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how do i alternate between different marker colors on matplotlib
psimplest might be to use a scatter plotp precodex range20 y 2nparrayx pylabscatterx y colorrgb codepre pa hrefhttpistackimgurcomaey5rpng relnofollowimg srchttpistackimgurcomaey5rpng altenter image description hereap pi think what tcaswell is suggesting as an alternative in his comment is using codeplotcode three times with different colors on the appropriate slicesp precodepylabplotx3 y3 ro pylabplotx13 y13 go pylabplotx23 y23 bo codepre
2
copydeepcopy raises typeerror on objects with selfdefined new method
pone problem is that codedeepcopycode and codecopycode have no way of knowing which arguments to pass to codenewcode therefore they only work with classes that dont require constructor argumentsp pthe reason why you can have codeinitcode arguments is that codeinitcode isnt called when copying an object but codenewcode must be called to create the new objectp pso if you want to control copying youll have to define the special codecopycode and codedeepcopycode methodsp precodedef copyself return self def deepcopyself memo return self codepre pby the way a hrefhttptechpuredangercom20070703patternhatesingletonsingletonsa are a hrefhttpblogsmsdncombscottdensmorearchive20040525140827aspxevila and not really needed in pythonp
2
where to put freezesupport in a python script
pon windows strongallstrong of your codemultiprocessingcodeusing code must be guarded by codeif name maincodep pso to be safe i would put all of your the code currently at the toplevel of your script in a codemaincode function and then just do this at the toplevelp precodeif name main main codepre psee the safe importing of main module subsection a hrefhttpsdocspythonorg2librarymultiprocessinghtmlwindowsherea for an explanation of why this is necessary you probably dont need to call codefreezesupportcode at all though it wont hurt anything to include itp pnote that its a best practice to use the codeif name maincode guard for scripts anyway so that code isnt unexpectedly executed if you find you need to codeimportcode your script into another script at some point in the futurep
2
django authentication and ajax urls that require login
pi would agree with a hrefhttpstackoverflowcomquestions312925djangoauthenticationandajaxurlsthatrequirelogin313015slottap pmake a check in the template if the user is logged in just put the link as usual if not put something like p precodelta hreflink onclickreturn loginpopupgt codepre pwhere loginpopup would return false if the user says cancelp pthis could be probably be done much easier in a hrefhttpjinjapocooorg2jinja2a through its a hrefhttpjinjapocooorg2documentationtemplatesmacrosmacrosap pif the template doesnt know which urls require the user to login you probably need to reconsider your designp pif you must i guess you can do the same thing that the django url dispatcher does to discover the view function br see codedjangocoreurlresolverscodep ponce youve grabbed the view function you can check if its decorated with loginrequired p pthis would be done in a custom tag probably br if you use jinja2 you wont need the tag just implement the function and expose it to the environment its simple but youll have to do a bit of reading on the api of jinja2p
2
python is there a wellknown function to normalize json representation of data
pto compare these objects you need to compare loaded dictsp precodeassert jsonloadss1 jsonloadss2 codepre pto ensure serializations are consistent with each other you may use a hrefhttpsdocspythonorg2libraryjsonhtmlbasicusagekeyword argument codesortkeyscodeap blockquote pif sortkeys is codetruecode default codefalsecode then the output of dictionaries will be sorted by keyp blockquote precodeassert jsondumpsd1 sortkeystrue jsondumpsd2 sortkeystrue codepre pif coded1 d2code equality above holds for any serializable data including nested structuresp
2
pandas how do i split text in a column into multiple rows
precodeimport pandas as pd import numpy as np df pddataframeitemqty 0 3 1 25 seatblocks 0 22181046 1 11336112 11337113 itemext 0 60 1 300 customername 0 mccartney paul 1 lennon john custnum 0 32363 1 31316 item 0 f04 1 f01 columnscustnumcustomernameitemqtyitemseatblocksitemext print df custnum customername itemqty item seatblocks itemext 0 32363 mccartney paul 3 f04 22181046 60 1 31316 lennon john 25 f01 11336112 11337113 300 codepre panother similar solution with chaining is use a hrefhttppandaspydataorgpandasdocsstablegeneratedpandasdataframeresetindexhtml relnofollowcoderesetindexcodea and a hrefhttppandaspydataorgpandasdocsstablegeneratedpandasseriesrenamehtml relnofollowcoderenamecodeap precodeprint dfdropseatblocks axis1 join dfseatblocks str splitexpandtrue stack resetindexdroptrue level1 renameseatblocks custnum customername itemqty item itemext seatblocks 0 32363 mccartney paul 3 f04 60 22181046 1 31316 lennon john 25 f01 300 11336112 1 31316 lennon john 25 f01 300 11337113 codepre hr <p>if in column are <strong>not</strong> <code>nan</code> values, the fastest solution is use <code>list</code> comprehension with <code>dataframe</code> constructor:</p> <pre><code>df = pd.dataframe(['a b c']*100000, columns=['col']) in [141]: %timeit (pd.dataframe(dict(zip(range(3), [df['col'].apply(lambda x : x.split(' ')[i]) for i in range(3)])))) 1 loop, best of 3: 211 ms per loop in [142]: %timeit (pd.dataframe(df.col.str.split().tolist())) 10 loops, best of 3: 87.8 ms per loop in [143]: %timeit (pd.dataframe(list(df.col.str.split()))) 10 loops, best of 3: 86.1 ms per loop in [144]: %timeit (df.col.str.split(expand=true)) 10 loops, best of 3: 156 ms per loop in [145]: %timeit (pd.dataframe([ x.split() for x in df['col'].tolist()])) 10 loops, best of 3: 54.1 ms per loop </code></pre> <p>but if column contains <code>nan</code> only works <a href="http://pandas.pydata.org/pandas-docs/stable/generated/pandas.series.str.split.html" rel="nofollow"><code>str.split</code></a> with parameter <code>expand=true</code> which return <code>dataframe</code> (<a href="http://pandas.pydata.org/pandas-docs/stable/text.html#splitting-and-replacing-strings" rel="nofollow">documentation</a>), and it explain why it is slowier:</p> <pre><code>df = pd.dataframe(['a b c']*10, columns=['col']) df.loc[0] = np.nan print (df.head()) col 0 nan 1 a b c 2 a b c 3 a b c 4 a b c print (df.col.str.split(expand=true)) 0 1 2 0 nan none none 1 a b c 2 a b c 3 a b c 4 a b c 5 a b c 6 a b c 7 a b c 8 a b c 9 a b c </code></pre>
2
numpy generating a sequence with a higher resolution within certain bounds
pyou could construct such a sequence by first making an array containing the spacings between each pair of points then taking a cumsum over thisp pfor example lets suppose i want to go from 0 to 50 everywhere in steps of 1 except between 20 and 30 where i want steps of 025p precodeimport numpy as np deltas nprepeat0 1 025 1 1 20 40 20 pts npcumsumdeltas codepre pplottingp precodefrom matplotlib import pyplot as plt fig ax pltsubplots1 1 axeventplotpts axmarginsx005 codepre pa hrefhttpistackimgurcomibinipng relnofollowimg srchttpistackimgurcomibinipng altenter image description hereap hr h3edith3 pid totally forgotten about a hrefhttpdocsscipyorgdocnumpyreferencegeneratednumpyrhtml relnofollowcodenprcodea which offers a very nice compact way to achieve the same thingp precodepts2 npr0201 2030025 30511 codepre pas well as specifying a step size manually you can also use an imaginary number as the step size which is equivalent to using codenplinspacecode to specifying the number of steps to take eg codenpr01020jcode is the same as codenplinspace0 10 20codep
2
how to parse sentences into tokens with either regex or toolkits
plook how easy it is using codebeautifulsoupcodep precodefrom bs4 import beautifulsoup data yesterdayltpersongtpeter smithltpersongtdrove toltlocationgtnew yorkltlocationgt soup beautifulsoupdata htmlparser for item in soup print item codepre pprintsp precodeyesterday ltpersongtpeter smithltpersongt drove to ltlocationgtnew yorkltlocationgt codepre pupd splitting nontag items into spaces and print every part on a new linep precodesoup beautifulsoupdata htmlparser for item in soup if not isinstanceitem tag for part in itemsplit print part else print item codepre pprintsp precodeyesterday ltpersongtpeter smithltpersongt drove to ltlocationgtnew yorkltlocationgt codepre phope that helpsp
2
using global variables between files
pthe problem is you defined codemylistcode from mainpy but subfilepy needs to use it here is a clean way to solve this problem move all globals to a file i call this file codesettingspycode this file is responsible for defining globals and initializing themp precode settingspy def init global mylist mylist codepre pnext your subfile can import globalsp precode subfilepy import settings def stuff settingsmylistappendhey codepre pnote that subfile does not call init that task belongs to mainpyp precode mainpy import settings import subfile settingsinit call only once subfilestuff do stuff with global var print settingsmylist0 check the result codepre pthis way you achieve your objective while avoid initializing global variables more than oncep
2
function name not defined
blockquote phave i not defined the name in the first line of the function def mainp blockquote pyes but python hasnt executed that definition yet put the function definition before the callp
2
python concatented string allow this to call a tuple
pthats not really what variable names are meant for the numbers 1 and 2 in codetuple1code and codetuple2code either mean something eg the code1code really means 1 person and the code2code 2 people or they dont theyre only placeholdersp pif they emdoem mean something you should probably use a dictionaryp precodegtgtgt mydata 1 123 2 456 gtgtgt mydata 1 1 2 3 2 4 5 6 gtgtgt mydata1 1 2 3 gtgtgt mydata2 4 5 6 codepre pif they dont and you simply have two tuples then you might as well use a listp precodegtgtgt mydata 123 456 gtgtgt mydata0 1 2 3 gtgtgt mydata1 4 5 6 gtgtgt for tup in mydata print tup 1 2 3 4 5 6 codepre pyou definitely dont need to use evalp
2
python method be aware the selfvariable changed
psince codevarcode is a class attribute you could simply check if the value for the instance is different from the parent classp precodeclass pobject var original def funcself if selfvar pvar print do a else print do b class c1p var changed class c2p pass c1 c1 c2 c2 c1func do a c2func do b codepre panother more general option might be to define a subclass of codepcode with the codefunccode method and use that as the parent for codec1code and codec2code classes then we can make use of a hrefhttpsdocspythonorg2libraryfunctionshtmlsuper relnofollowsupera to access the parent attribute as followsp precodeclass pobject var original class pchildp def funcself if selfvar superpchild selfvar print do a else print do b class c1pchild var changed class c2pchild pass c1 c1 c2 c2 c1func c2func codepre
2
how to declare member variable in python base class which can be accessed in derived
pinstance variables are always accessed through the class instance itself inside the method this is by convention known as codeselfcode so you need to use codeselfheaderscode etcp pnote though that by defining codeheaderscode at the top of the class you have defined a emclassem variable which is shared by all members you dont want this and there is no need to define codeheaderscode there just assign it within codeinitcodep pplus as storyteller points out youll need to call the superclass codeinitcode method manually inside the derived class methods since that defines the attribute in the first placep precodesuperposthttprequest selfinit codepre pand in order for that to work as abarnert points out youll need to inherit your base class from codeobjectcodep pfinally please do use pep8compliant names codeposthttprequestcode etcp
2
use glob to find arbirary length numbers
pyou are probably confusing regular expression syntax with glob constructs code09code in globbing means a single digit followed by zero or more of emanyem character so drop the codecodep pin emextended globbingem there is a qualifier of one or more but that is not supported by codeglobcode so there is little choice but to use a regular expression ie do your own filename pattern matching there are several ways to do this here is onep precodeimport os import re files for fname in oslistdir if rematchrmyfile09txt fname filesappendfname print files codepre pnote that the re is not exactly the same as yours i use codecode which means one of more of the preceding pattern an codecode would mean zero or more so the digits would be optional which could be what you want im not surep pthe bulk of the code could be done as a list comprehension but that would arguably loose some readabilityp precodefiles fname for fname in oslistdir if rematchrmyfile09txt fname codepre
2
doing shell backquote in python
pthe a hrefhttpdocspythonorglibrarysubprocesshtmlreplacingbinshshellbackquote relnofollowossubprocess documentationa describes how to replace backquotesp precodeoutputmycmd myarg gt output popenmycmd myarg stdoutpipecommunicate0 codepre
2
anagrams code resulting in infinite results
pthis is not an infinity of results this is 13 words a bit over 6 billions you are facing a combinatorial explosionp p 13 factorialp
2
combine multiple text files line by line in python
pin the command linep precode paste a b c 1 a x 2 b y 3 c z codepre
2
how to load python script in interactive shell
pfrom the docsp precode python help usage usrbinpython27 option c cmd m mod file arg options and arguments and corresponding environment variables b dont write pyco files on import also pythondontwritebytecodex c cmd program passed in as string terminates option list d debug output from parser also pythondebugx e ignore python environment variables such as pythonpath h print this help message and exit also help i inspect interactively after running script forces a prompt even if stdin does not appear to be a terminal also pythoninspectx codepre puse codeicode optionp
2
fill between two vertical lines in matplotlib
pit sounds like you want a hrefhttpmatplotliborgapipyplotapihtmlmatplotlibpyplotaxvspancodeaxvspancodea rather than one of the fill between functions the differences is that codeaxvspancode and a hrefhttpmatplotliborgapipyplotapihtmlmatplotlibpyplotaxhspancodeaxhspancodea will fill up the entire y or x extent of the plot regardless of how you zoomp pfor example lets use codeaxvspancode to highlight the xregion between 8 and 14p precodeimport matplotlibpyplot as plt fig ax pltsubplots axplotrange20 axaxvspan8 14 alpha05 colorred pltshow codepre pimg srchttpistackimgurcomjaq9lpng altenter image description herep pyou could use codefillbetweenxcode to do this but the extents both x and y of the rectangle would be in emdata coordinatesem with codeaxvspancode the yextents of the rectangle default to 0 and 1 and are in emaxes coordinatesem in other words percentages of the height of the plot p pto illustrate this lets make the rectangle extend from 10 to 90 of the height instead of taking up the full extent try zooming or panning and notice that the yextents say fixed in display space while the xextents move with the zoompanp precodeimport matplotlibpyplot as plt fig ax pltsubplots axplotrange20 axaxvspan8 14 ymin01 ymax09 alpha05 colorred pltshow codepre pimg srchttpistackimgurcomwwzzipng altenter image description herep
2
assigning a value to a string item in list
pyou simply define a list of stringsp precodecardnames ace2345678910jackqueenking codepre pnow if the card has value codevcode you can get the corresponding name with codecardnamesv1code for instancep precodev 5 printi have a scardnamesv1 codepre pin that case the value for the jack is 11 for queen 12 and for king 13 for instance using codepythoncodes interactive shellp precode python python 279 default apr 2 2015 153321 gcc 492 on linux2 type help copyright credits or license for more information gtgtgt cardnames ace2345678910jackqueenking gtgtgt v12 gtgtgt printi have a scardnamesv1 i have a queen gtgtgt v7 gtgtgt printi have a scardnamesv1 i have a 7 gtgtgt v1 gtgtgt printi have a scardnamesv1 i have a ace gtgt;&gt; v=13 &gt;&gt;&gt; print("i have a %s"%cardnames[v-1]) i have a king </code></pre> <p>or using <code>python3</code>:</p> <pre><code>$ python3 python 3.4.3 (default, mar 26 2015, 22:03:40) [gcc 4.9.2] on linux type "help", "copyright", "credits" or "license" for more information. &gt;&gt;&gt; cardnames = ["ace","2","3","4","5","6","7","8","9","10","jack","queen","king"] &gt;&gt;&gt; v=12 &gt;&gt;&gt; print("i have a %s"%cardnames[v-1]) i have a queen &gt;&gt;&gt; v=7 &gt;&gt;&gt; print("i have a %s"%cardnames[v-1]) i have a 7 &gt;&gt;&gt; v=1 &gt;&gt;&gt; print("i have a %s"%cardnames[v-1]) i have a ace &gt;&gt;&gt; v=13 &gt;&gt;&gt; print("i have a %s"%cardnames[v-1]) i have a king </code></pre>
2
stack of 2d plot
pthis can be done with the simple a hrefhttpmatplotlibsourceforgenetmpltoolkitsmplot3dtutorialhtmlmpltoolkitsmplot3daxes3dplot relnofollowplot commandap precodefrom mpltoolkitsmplot3d import axes3d import matplotlibpyplot as plt import numpy as np nangles 200 fig pltfigure ax figaddsubplot111 projection3d nvals 0 2 4 10 20 40 100 for iy in rangelennvals n nvalsiy x nparangenangles floatnangles y nponesnanglesiy set y position to same value with regular step z npsinnxnppi axplotx y z axsetylabeln axsetyticklabelsnvals update y ticks set at regular step to your vals pltsavefigstackedplotpng pltshow codepre pwhat ive shown is a simple start and adjusting the cosmetic aspects of the plot is probably a good challenge to learnexplore more of pythonmatplotlibp pimg srchttpistackimgurcomulzkhpng altenter image description herep
2
python mystery infinite loop
premember array indices start from 0 so ifp precodea 0 4 0 3 2 codepre pthen codea3 3codep pso this linep precodex ax codepre pnever sets codexcode to anything other than 3p
2
how do i import data with different types from file into a python numpy array
puse a hrefhttpdocsscipyorgdocnumpyreferencegeneratednumpygenfromtxthtmlcodenumpygenfromtxtcodeap precodeimport numpy as np npgenfromtxtfilename dtype none array1 20 bucklemyshoe 3 40 margerydoor dtypef0 lti4 f1 ltf8 f2 s14 codepre
2
how to use bulk api to store the keywords in es by using python
pthe current approaches mentioned here use python list for the es update its not a good solution today especially when you need to add millions of data to esp pbetter approach is using python generators process gigs of data without going out of memory or compromising much on speedp pbelow is an example snippet from a practical use case adding data from nginx log file to es for analysisp precodedef decodenginxlognginxfd for eachline in nginxfd filter out the below from each log line remoteaddr timestamp index for elasticsearch typically timestamp idx esfieldskeys remoteaddr timestamp url status esfieldsvals remoteaddr timestamp url status we return a dict holding values from each line esnginxd dictzipesfieldskeys esfieldsvals return the row on each iteration yield idx esnginxd lt note the usage of yield def esaddbulknginxfile the nginx file can be gzip or just text open it appropriately es elasticsearchhosts host localhost port 9200 note the round brackets this is for a generator k index nginx type logs id idx source esnginxd for idx esnginxd in decodenginxlognginxfd helpersbulkes k now just run it esaddbulknginx1loggz codepre pthis skeleton demonstrates the usage of generators you can use this even on a bare machine if you need to and you can go on expanding on this to tailor to your needs quicklyp ppython elasticsearch reference a hrefhttpelasticsearchpyreadthedocsioenmasterhelpershtml relnofollowhereap
2
functional way to create new list by processing elements of another list
blockquote pwhat is the simplest way of creating one list from anotherp blockquote puse a a hrefhttpsdocspythonorg2tutorialdatastructureshtmllistcomprehensions relnofollowlist comprehensionap precodeans myreadfunctionfilename for filename in filenames codepre
2
slice specific characters in csv using python
pnumpy is great when you want to load in an array of numbers the format you have here is too complicated for numpy to recognize so you just get an array of strings thats not really playing to numpys strengthp pheres a simple way to do it without numpyp precoderesult with opencsvfiler as f for line in f row for text in linesplitt matchresearch0909text if match rowappendmatchgroup1 else rowappendna resultappendrow printresult codepre pyieldsp precode 00 01 00 na 01 00 codepre pon this datap precode002310379483756915 01341011124127519900 00741022328301819900 2310379483756915 01341011124127519900 00741022328301819900 codepre
2
how to search backwards in python
puse strrfind method to search for the occurence of a string in the reverse direction a hrefhttpstackoverflowcomquestions3537717pythonreversefindinstringthisa question should also give you some insight on how to go aboutp
2
storing username and password into a dictionary
pyou dont you save a hash into a dictionary a hash is simpley a non reversable encodingp peg codemd5password 5f4dcc3b5aa765d61d8327deb882cf99code p phowever there is no real way to go from that back to the password p pcodenothingdoesthis5f4dcc3b5aa765d61d8327deb882cf99 passwordcode p pnot entirely true but close enough fo the conceptp precodeimport hashlib def createusers users while true username rawinputenter username password rawinputenter password usersusername hashlibmd5passwordhexdigest if rawinputcontinue0lower y return users def loginuserdict username rawinputusername password rawinputpassword return userdictgetusernamenone hashlibmd5passwordhexdigest users createusers if loginusers print double winning else print you lose sucka codepre pas pointed out md5 is not a very secure hash there are much better ones to use sha256 is pretty good still i think bcrypt is even better for some definition of better however md5 is a simple hash to help with understanding what they arep
2
how do i split words in python while keeping in consideration words with hyphens
pno need for a regexp precodegtgtgt fatfree milksplit fatfree milk codepre pif you want to split on any nonword character that is not a hyphen you can use a negated character group like in johns answer or a negative lookahead which might be slightly more flexiblep precodegtgtgt resplitrw fatfree milk with cream fatfree milk with cream codepre
2
what is the elegantpythonic way to keep variables in scope yet also catch exceptions
pthe obvious alternative would be to do the false initialization in the codeexceptcode blockp precodetry proxytest isproxyworkingproxy except timeouterror proxytest none codepre pwhether this is easiermore appropriate than your constructions depends on how complicated the logic is in the middle thoughp
2
python looping to other functions using one function
pat the bottom where you call codegame1code add calls for codegame2code etcp precodegame1 game2 game3 codepre
2
how to show chinese word not unicode word
pby default printing a larger builtin structure gives the codereprcode of each of the elements if you want the codestrcodecodeunicodecode instead then you need to iterate over the sequence yourselfp precodea u u jointokentext for token in u print a codepre
2
find minimum window substring
passume that string s and t only contains codeazcode characters 26 charactersp ul lipfirst create an array codecountcode which store the frequency of each characters in codetcodepli lipprocess each character in s maintaining a window codel rcode which will be the current minimum window that contains all characters in tpli lipwe maintain an array codecurcode to store the current frequency of characters in window if the frequency of the character at the left end of the window is greater than needed frequency we increase codelcodepli ul psample codep precode intcount new int26 forint i 0 i lt tlength i countti a int need 0number of unique characters in t forint i 0 i lt 26 i ifcounti gt 0 need int l 0 r 0 int count 0 int result intcur new int26 forint i 0 i lt slength i cursi a r i ifcursi a countsi a count update the start of the window whilecursl a gt countsl a cursl a l ifcount need result minresult r l 1 codepre peach character in s will be processed at most two times which give us on complexity.</p>
2
how to get all keys from dictionary that specified values
pyou can do it like thisp precodekey for key value in somedictitems if value 2 codepre pthis uses a list comprehension to iterate through the pairs of codekey valuecode items selecting those keys whose value equals 2p pnote that this requires a linear search through the dictionary so it is emonem if this performance is not acceptable you will probably need to create and maintain another data structure that indexes your dictionary by valuep
2
getting html stripped of script and style tags with beautifulsoup
pcodeunicode soup code gives you the htmlp palso what you want is thisp precodefor elem in soupfindallscript style elemextract codepre
2
import order coding standard
phave a look at a hrefhttpspypipythonorgpypiisort relnofollowhttpspypipythonorgpypiisorta or a hrefhttpsgithubcomtimothycrosleyisort relnofollowhttpsgithubcomtimothycrosleyisortap blockquote pisort parses specified files for global level import lines imports outside of try excepts blocks functions etc and puts them all at the top of the file grouped together by the type of importp ul lifuture li lipython standard library li lithird party li licurrent python project li liexplicitly local before import as in from import x li ul pcustom separate sections defined by forcedseparate list in configuration file inside of each section the imports are sorted alphabetically isort automatically removes duplicate python imports and wraps long from imports to the specified line length defaults to 80p blockquote pa hrefhttpspypipythonorgpypiflake8isort relnofollowhttpspypipythonorgpypiflake8isorta plugs this functionality into flake8p
2
assign next n iterations to tuple
pyou can use codeitertoolsislicecode to select items from an iterable note that iterators are iterable but not every iterable is an iterator with a codenextcode or codenextcode in python3 methodp precodegtgtgt from itertools import islice gtgtgt iterator x for x in a b c d e gtgtgt tupleisliceiterator 3 a b c codepre palternatively a simple comprehensionp precodegtgtgt iterator x for x in a b c d e gtgtgt tuplenextiterator for in range3 a b c codepre pthe name codecode has no special meaning for the interpreter outside of interactive sessions where it stores the result of the last executed statement but is noticed as the name for a throwawayvariable by python programmersp
2
how to automate my three bash scripts over several folders with files
pon linux use a a hrefhttpman7orglinuxmanpagesman5crontab5html relnofollowcrontab5a to schedule your various shell scripts they could run in parallelp pyou might also look into a hrefhttpswwwgnuorgsoftwareparallel relnofollowgnu parallela but i guess you dont need itp pat last a shell script could schedule another one using a hrefhttpwwwcomputerhopecomunixuathtm relnofollowata or codebatchcode for example codedecodeshcode might perhaps end with codebatch f sortshcode or codeat f sortsh now 10 minutescode p pand you might use some more powerful scripting language eg python guile perl p pbtw be sure to test success of every script and even parts inside them use a hrefhttpman7orglinuxmanpagesman1logger1html relnofollowlogger1a to emit log messages perhaps after every step or command which lasts more than half an a hour and at start and end of every script check daily the logsp pat last i dont understand why only one database script can run at a time most real dbms postgresql mongodb mariadb etc but not sqlite can run or be configured to run several database clients concurrently accessing the same database or of course different ones read more about a hrefhttpsenwikipediaorgwikiacid relnofollowacida propertiesp pdoing that on some external usb hard disk is imho a mistake because such hardware has limited reliability and is often slow you should consider having some server perhaps a good desktop might have such a role you might need an a hrefhttpsenwikipediaorgwikiuninterruptiblepowersupply relnofollowupsa to avoid power glitchesp pif this complex processing and the processed data has some value to you you should upgrade both the hardware get a server machine possibly with an ups and a hrefhttpsenwikipediaorgwikieccmemory rel="nofollow">ecc ram</a> and, if the data fits, an <a href="https://en.wikipedia.org/wiki/solid-state_drive" rel="nofollow">ssd</a>) and the software (use real dbms, care for failure). estimate the cost of failure and/or data loss (remember to take into account your time). perhaps renting some cloud computing or storage could be interesting (or simply a <a href="https://en.wikipedia.org/wiki/virtual_private_server" rel="nofollow">vps</a> hosted linux system with backup, you can get one for about two dozens of dollars or euros every month: <a href="https://www.kimsufi.com/" rel="nofollow">kimsufi</a>, <a href="https://www.ovh.com/" rel="nofollow">ovh</a>, <a href="http://www.rackspace.com/" rel="nofollow">rackspace</a>, <a href="http://aws.amazon.com" rel="nofollow">aws</a>, ...)...</p>
2
singular matrix issue with numpy
pby definition by multiplying a 1d vector by its transpose youve created a singular matrixp peach row is a linear combination of the first row p pnotice that the second row is just 8x the first rowp plikewise the third row is 50x the first rowp ptheres only one independent row in your matrixp
2
outofcore training of scikits linearsvc classifier
pas far as i know nonincremental implementations like linearsvc would need the entire data set to train on unless you create an incremental version of it you might be unable to use linearsvcp pthere are classifiers in scikitlearn that can be used incrementally just like in the guide you found wherein it was using an sgdclassifier the sgdclassifier has the partialfit method which allows you to train it in batches there are a couple of other classifiers that support incremental learning such as a hrefhttpscikitlearnorgstablemodulesgeneratedsklearnlinearmodelsgdclassifierhtml relnofollowsgdclassifiera a hrefhttpscikitlearnorgstablemodulesgeneratedsklearnnaivebayesmultinomialnbhtml relnofollowmultinomial naive bayesa and a hrefhttpscikitlearnorgstablemodulesgeneratedsklearnnaivebayesbernoullinbhtml relnofollowbernoulli naive bayesap
2
python34 on sublime text 3
pyou need to provide the full path to python3 since sublime text does not read your codebashprofilecode file open up terminal type codewhich python3code and use that full pathp precode cmd pathtopython3 file selector sourcepython fileregex file line 09 codepre
2
matplotlib wont write approx latex character in legend
ptry using a raw string literal coderuc approx 01fcodep precodein 8 pltscatter05 05 05 05 labelruc approx 01f22 out8 ltmatplotlibcollectionspathcollection at 0x7f799249e550gt in 9 pltlegendfancyboxtrue locbest out9 ltmatplotliblegendlegend at 0x7f79925e1550gt in 10 pltshow codepre pimg srchttpistackimgurcomrd1okpng altenter image description herep pthe reason this is happening is as follows p ul lipwithout the codercode infront of the string literal the string is interpreted by the interpreter as p puc a pprox 220pli lipthe codeacode is a special escaped character for the ascii bell codebelcodepli lithis interpreted string is then passed to the tex parser however because codeapproxcode got mashed up the tex parser doesnt know how to convert your string to proper tex li ul pto make sure backslashes codecode in the string arent creating weird escaped characters add the codercode out frontp
2
getting a list of child entities in app engine using getbykeyname python
pjust create a key list and do a get on itp precodeentities modelgetbykeynamekeynames contentkeys dbkeyfrompathmodel name contentmodel name for name in keynames contententities contentmodelgetcontentkeys codepre pnote that i assume the keyname for each contentmodel entity is the same as its parent model for a 11 relationship it makes sense to reuse the keynamep
2
what language could i use for fast execution of this database summarization task
pyou could use smarter data structures and still use python ive ran your reference implementation and my python implementation on my machine and even compared the output to be sure in resultsp pthis is yoursp precode time python refpy lt datalargetxt gt reflargetxt real 1m57689s user 1m56104s sys 0m0573s codepre pthis is minep precode time python mypy lt datalargetxt gt mylargetxt real 1m35132s user 1m34649s sys 0m0261s diff mylargetxt reflargetxt echo 0 codepre pand this is the sourcep precodeusrbinpython coding utf8 import sys import heapq top5 for line in sysstdin aa bb cc linesplit we want the top 5 for each distinct value of aa there are hundreds of thousands of values of aa bb floatbb if aa not in top5 top5aa current top5aa if lencurrent lt 5 heapqheappushcurrent bb cc else if current0 lt bb cc heapqheapreplacecurrent bb cc for aa in top5 current top5aa while lencurrent gt 0 bb cc heapqheappopcurrent print aa bb cc codepre pstrongupdatestrong know your limits ive also timed a noop code to know the fastest possible python solution with code similar to the originalp precode time python nooppy lt datalargetxt gt nooplargetxt real 1m20143s user 1m19846s sys 0m0267s codepre pand the nooppy itselfp precodeusrbinpython coding utf8 import sys import heapq top5 for line in sysstdin aa bb cc = line.split() bb = float(bb) if aa not in top_5: top_5[aa] = [] current = top_5[aa] if len(current) &lt; 5: current.append((bb, cc)) for aa in top_5: current = top_5[aa] current.sort() for bb, cc in current[-5:]: print aa, bb, cc </code></pre>
2
humanize numbers with python
pthis library doesnt seem to support your particular use case but you could add the functionality by editing codenumberspycode lines 54 and 55 top precodepowers 10 x for x in 3 6 9 12 15 18 21 24 27 30 33 100 humanpowers nthousand nmillion nbillion ntrillion nquadrillion nquintillion nsextillion nseptillion noctillion nnonillion ndecillion ngoogol codepre
2
why unittest2 methods are camelcase if nameswithunderscores are prefered
pfrom a hrefhttpspypipythonorgpypiunittest2unittest2 websiteap blockquote punittest2 is a backport of the new features added to the unittest testing framework in python 27 it is tested to run on python 24 27p pto use unittest2 instead of unittest simply replace import unittest with import unittest2p blockquote pits a bit confusing as from a version 2 is not expected to be a backport but a new major release with probably new features anyway the main idea is creating a backport where all the user has to do is changing the import statement for this they could not change their method signaturesp palso from a hrefhttpdocspythonorg2libraryunittesthtmlunittest websiteap blockquote pthe python unit testing framework sometimes referred to as pyunit is a python language version of junit by kent beck and erich gamma junit is in turn a java version of kents smalltalk testing framework each is the de facto standard unit testing framework for its respective languagep blockquote pso this explains the whole resemblance between the frameworks and emprobablyem the camel case notationp
2
imported a python module why does a reassigning a member in it also affect an import elsewhere
ptest2pyp precodeimport config as conf def test2 printidconftestvar printconftestvar codepre ptest1pyp precodeimport config as conf def test1 conftestvar test1 printidconftestvar codepre pchange code like this p pand run codemainpycodep precodeinitialvalue 140007892404912 test1 140007892404912 test1 codepre pso you can see that in both cases you are changing value of the same variable see these codeidcodes are same p
2
pandas read excel do not parse numbers
paccording to a hrefhttpsgithubcompydatapandasissues5891 relnofollowthis issuea its a known problem with pandasp
2
print r correctly in console
pthis is because print always generates a new line whenever you use r or not try sysstdout insteadp precodeimport time sys for i in range101 sysstdoutwritestri r sysstdoutflush timesleep3 codepre
2
how to find element attribute using lxml
pyou need to retrieve the node itself not its textp precoderating nodexpathtrating namespaces thttpexamplenamespace print rating0attribsystem codepre
2
dividing dataframe columns and getting zerodivisionerror float division by zero
pyou can initially set all values to zero then create a mask locating all rows with a valid denominator ie where codepowercode is greater than zero codegt0code finally use the mask together with codeloccode to calculate codesecondsteppowercodep precodedfsecondsteppower 0 mask dfaveragepowergt0 dflocmask secondsteppower dflocmask firstpower dflocmask averagepower codepre
2
create a slightly modified copy of a python tuple
pi would be inclined to use a a hrefhttpsdocspythonorg2librarycollectionshtmlcollectionsnamedtuple relnofollowcodenamedtuplecodea instead and use the a hrefhttpsdocspythonorg2librarycollectionshtmlcollectionssomenamedtuplereplace relnofollowcodereplacecode methodap precodegtgtgt from collections import namedtuple gtgtgt test namedtupletest foo bar baz gtgtgt t1 test1 2 3 gtgtgt t1 testfoo1 bar2 baz3 gtgtgt t2 t1replacebart1bar1 gtgtgt t2 testfoo1 bar3 baz3 codepre pthis also gives semantic meaning to the individual elements in the tuple ie you refer to codebarcode rather than just the code1codeth elementp
2
how do you retrieve items from a dictionary in the order that theyre inserted
pive used stabledict before with good successp pa hrefhttppypipythonorgpypistabledict02 relnofollowhttppypipythonorgpypistabledict02ap
2
pythondetect if the current line in file read is the last one
precodeimport os path myfiletxt size ospathgetsizepath with openpath as f for line in f size lenline if not size printthis is the last line printline codepre
2
python script to convert from numbers to words for printing cheques
phave written a custom converter with the foll featuresp ul linumber to word converter that can be used for numbers from 0 to 999999999 catering to indian subcontinent ie lacs and crore the range is big enough to accomodate lot of use casesli liincludes paisa support upto 2 decimal places roundedli liinspired by the post at a hrefhttpwwwblogpythonlibraryorg20101021pythonconvertingnumberstowords relnofollowhttpwwwblogpythonlibraryorg20101021pythonconvertingnumberstowordsali lipprofiling information this script has lesser performace in terms of execution time of 0458 seconds against 0237 seconds of the above script for exactly 10000 runsp precodeclass number2wordsobject def initself initialise the class with useful data selfwordsdict 1 one 2 two 3 three 4 four 5 five 6 six 7 seven 8 eight 9 nine 10 ten 11 eleven 12 twelve 13 thirteen 14 fourteen 15 fifteen 16 sixteen 17 seventeen 18 eighteen 19 nineteen 20 twenty 30 thirty 40 forty 50 fifty 60 sixty 70 seventy 80 eighty 90 ninty selfpowernamelist thousand lac crore def convertnumbertowordsself number check if there is decimal in the number if yes process them as paisa part formstring strnumber if formstringfind 1 withoutdecimal decimalpart formstringsplit paisapart strroundfloatformstring 2)).split('.')[1] inpaisa = self._formulatedoubledigitwords(paisapart) formstring, formnumber = str(withoutdecimal), int(withoutdecimal) else: # process the number part without decimal separately formnumber = int(number) inpaisa = none if not formnumber: return 'zero' self._validatenumber(formstring, formnumber) inrupees = self._convertnumbertowords(formstring) if inpaisa: return 'rs. %s and %s paisa' % (inrupees.title(), inpaisa.title()) else: return 'rs. %s' % inrupees.title() def _validatenumber(self, formstring, formnumber): assert formstring.isdigit() # developed to provide words upto 999999999 if formnumber &gt; 999999999 or formnumber &lt; 0: raise assertionerror('out of range') def _convertnumbertowords(self, formstring): msbs, hundredthplace, teens = self._getgroupofnumbers(formstring) wordslist = self._convertgroupstowords(msbs, hundredthplace, teens) return ' '.join(wordslist) def _getgroupofnumbers(self, formstring): hundredthplace, teens = formstring[-3:-2], formstring[-2:] msbunformattedlist = list(formstring[:-3]) #---------------------------------------------------------------------# msbs = [] tempstr = '' for num in msbunformattedlist[::-1]: tempstr = '%s%s' % (num, tempstr) if len(tempstr) == 2: msbs.insert(0, tempstr) tempstr = '' if tempstr: msbs.insert(0, tempstr) #---------------------------------------------------------------------# return msbs, hundredthplace, teens def _convertgroupstowords(self, msbs, hundredthplace, teens): wordlist = [] #---------------------------------------------------------------------# if teens: teens = int(teens) tensunitsinwords = self._formulatedoubledigitwords(teens) if tensunitsinwords: wordlist.insert(0, tensunitsinwords) #---------------------------------------------------------------------# if hundredthplace: hundredthplace = int(hundredthplace) if not hundredthplace: # might be zero. ignore. pass else: hundredsinwords = '%s hundred' % self.wordsdict[hundredthplace] wordlist.insert(0, hundredsinwords) #---------------------------------------------------------------------# if msbs: msbs.reverse() for idx, item in enumerate(msbs): inwords = self._formulatedoubledigitwords(item) if inwords: inwordswithdenomination = '%s %s' % (inwords, self.powernamelist[idx]) wordlist.insert(0, inwordswithdenomination) #---------------------------------------------------------------------# return wordlist def _formulatedoubledigitwords(self, doubledigit): if not int(doubledigit): # might be zero. ignore. return none elif self.wordsdict.has_key(int(doubledigit)): # global dict has the key for this number tensinwords = self.wordsdict[int(doubledigit)] return tensinwords else: doubledigitstr = str(doubledigit) tens, units = int(doubledigitstr[0])*10, int(doubledigitstr[1]) tensunitsinwords = '%s %s' % (self.wordsdict[tens], self.wordsdict[units]) return tensunitsinwords if __name__ == '__main__': wgenerator = number2words() print wgenerator.convertnumbertowords(100000) </code></pre></li> </ul>
2
python nameerror self is not defined
pjust in case someone happens upon this and is looking for a solution not having to do with indentation this is a good reference for how when to use codeselfcodep pa hrefhttpstackoverflowcomquestions1802971nameerrornameselfisnotdefinednameerror name 39self39 is not definedap
2
wrong output when adding list to dict
pyoure always appending to the same list thus all the dictionary values end up pointing to the same list you want to append to a different list each timep precoded a numpyarray6 12 18 24 30 for monthstomaturity in a l for i in range6 354 6 if i lt monthstomaturity lappendmonthstomaturity i else lappend0 dmonthstomaturity l codepre
2
more efficient way split quoted string by space with python
pthis looks a bit like csv i wonder if the csv module can be abused into working with thisp precodegtgtgt for row in csvreaderline delimiter print reprrow 0278 0264 11311652174 101034120080 08apr2012235908 0800 shenzhenanjukecom get ajaxpropextproid104178677ampcommid97047ampbrokerid262646amprand0905798233768953 http10 200 10914 httpshenzhenanjukecompropview104178677 mozilla40 compatible msie 60 windows nt 51 sv1 360se 11480230198 026af756c5df3edab96af31a39f7c65e codepre
2
organising my python project
ppython doesnt force you into javas nasty oneclassperfile style in fact its not even considered good style to put each class in a separate file unless they are huge if they are huge you probably have to do refactoring anyway instead you should group similar classes and functions in modules for example if you are writing a gui calculator your package layout might look like thisp precodeamazingcalc initpy this makes it a python package and importable evaluatepy contains the code to actually do calculations mainpy starts the application uipy contains the code to make a pretty interface codepre
2
appengine can i fetch an internal url
pthis will not work at all with the development server it is singlethreaded so trying to load one of your apps urls while inside one of its request handlers will hang until the urlfetch times outp pit should work with no problems at all in productionp pto get around the development server limitation you should run two instances on different portsp
2
antlr4 and the python target
pi hear you having the same issues right now the python documentation for v4 is useless and v3 differs to much to be usable im thinking about switching back to java to implement my stuffp pregarding your code i think your own custom listener has to inherit from the generated hellolistener you can do the printing therep palso try parsing invalid input to see if the parser starts at all im not sure about the line with getattrparser rulename though i followed the steps in the unfortunately very short documentation for the antlr4 python target a hrefhttpstheantlrguyatlassiannetwikidisplayantlr4pythontarget relnofollowhttpstheantlrguyatlassiannetwikidisplayantlr4pythontargetap pyou can also find some documentation about the listener stuff there hope it helpsp
2
why does my code work from interactive shell but not when run from a file
pyou named your program pprintpy so at the line codeimport pprintcode it tries to import itself it succeeds but emyourem pprintpy doesnt contain anything called prettyprinterp pchange your codes name and to be clear delete any pprintpyc or pprintpyo filesp
2
numpy find first index of value fast
pin case of sorted arrays codenpsearchsortedcode worksp
2
pep 8 why no spaces around in keyword argument or a default parameter value
pimo leaving out the spaces for args provides cleaner visual grouping of the argvalue pairs it looks less clutteredp
2
how to use variables in sql statement in python
precodecursorexecuteinsert into table values s s s var1 var2 var3 codepre pnote that the parameters are passed as a tuplep pthe database api does proper escaping and quoting of variables be careful not to use the string formatting operator codecode becausep ol liit does not do any escaping or quotingli liit is prone to uncontrolled string format attacks eg a hrefhttpenwikipediaorgwikisqlinjectionsql injectionali ol
2
xarraydatasetwhere method forcechanges dtype of dataarrays to float
pthats because with numpy which xarray uses underthehood ints dont have a way of representing codenancodes so with most codewherecode results the type needs to be coerced to floatsp pif codedroptruecode and every value that is masked is dropped thats not actually a constraint you could have the new array retain its dtype because theres no need for codenancode values thats not in xarray at the moment but could be an additional featurep
2
python fill hollow object
pif you use a hrefhttpwwwscipyorg relnofollowcodescipycodea you can do this in one line with a hrefhttpdocsscipyorgdocscipyreferencegeneratedscipyndimagemorphologybinaryfillholeshtmlscipyndimagemorphologybinaryfillholes relnofollowcodebinaryfillholescodea strongand this works in ndimensionsstrong with your examplep precodeimport numpy as np from scipy import ndimage shapenparray 000000000000 000111111000 001100011100 000100100000 001000010000 001000010000 001111110000 000000000000 shapendimagebinaryfillholesshape 1 output 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 1 1 1 1 1 1 0 0 0 0 0 1 1 1 1 1 1 1 1 0 0 0 0 0 1 1 1 1 0 0 0 0 0 0 0 1 1 1 1 1 1 0 0 0 0 0 0 1 1 1 1 1 1 0 0 0 0 0 0 1 1 1 1 1 1 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 codepre
2
typeerror unbound method when trying to mock a classmethod
ppython functions are a hrefhttpsdocspythonorg2howtodescriptorhtml relnofollowdescriptorsa and python binds these to the instance they are looked up on or in the case of codeclassmethodcode to the class because you didnt use the codeclassmethodcode decorator on the replacement function it is being bound wrongly as a regular method instead so no codeclscode is being passed inp psimply wrap the target in a codeclassmethodcode decorator manuallyp precodewith mockpatchobjectmyclass mymethod classmethodmockedmethod myclassmymethod codepre phere i applied the codeclassmethodcode decorator manually but you could also just use it as intended as a decorator directly on the target functionp precodeclassmethod def mockedmethodcls printi want this method to get called with mockpatchobjectmyclass mymethod mockedmethod myclassmymethod codepre pdemop precodegtgtgt import mock gtgtgt class myclassobject classmethod def mymethodcls printmymethod gtgtgt def mockedmethodcls printi want this method to get called gtgtgt with mockpatchobjectmyclass mymethod classmethodmockedmethod myclassmymethod i want this method to get called codepre
2
how to make a function print many times on the same line eg printtest3
pyou can change your code to this onep precodedef myprinttimes printtimesfoobar foo randomrandint1 6 myprintfoo codepre
2
python postgres can i fetchall 1 million rows
pthe solution burhan pointed out reduces the memory usage for large datasets by only fetching single rowsp blockquote prow cursorfetchonep blockquote phowever i noticed a significant slowdown in fetching rows onebyone i access an external database over an internet connection that might be a reason for itp phaving a server side cursor and fetching bunches of rows proved to be the most performant solution you can change the sql statements as in alecxe answers but there is also pure python approach using the feature provided by psycopg2p precodecursor conncursornameofthenewserversidecursor cursorexecute select from table limit 1000000 while true rows cursorfetchmany5000 if not rows break for row in rows do something with row pass codepre pyou find more about server side cursors in the a hrefhttpwikipostgresqlorgwikiusingpsycopg2withpostgresqlfetchrecordsusingaserversidecursor relnofollowpsycopg2 wikiap
2
using requests with tls doesnt give sni support
plukasa answer is correct with the present from github requests remember to add openssl in your system too apart from the pip dependencies he mentionsp pif for deployment reasons you prefer a stable requests version like the 123 in pip you can monkey patch that one to work with sni like thisp precodeimport requests def filenoself return selfsocketfileno def closeself return selfconnectionshutdown requestspyopensslwrappedsocketclose close requestspyopensslwrappedsocketfileno fileno codepre
2
how do i find the time difference between two datetime objects in python
pjust subtract one from the other you get a codetimedeltacode object with the differencep precodegtgtgt import datetime gtgtgt d1 datetimedatetimenow gtgtgt d2 datetimedatetimenow after a 5second or so pause gtgtgt d2 d1 datetimetimedelta0 5 203000 codepre pyou can convert codedddayscode codeddsecondscode and codeddmicrosecondscode to minutesp
2
what is the best data structure for storing a set of four or more values
pthere isnt a single data structure built into python that does everything you want but its fairly easy to use a combination of the ones it has to achieve your goals and do so fairly efficientlyp pfor example say your input was the following data in a commaseparatedvalue file called codeemployeescsvcode with field names defined as shown by the first linep pre classlangnone prettyprintoverridecodenameageweightheight bob barker251756ft 2in ted kingston281635ft 10in mary manson271405ft 6in sue sommers271325ft 8in alice toklas241245ft 6in codepre pthe following is working code which illustrates how to read and store this data into a list of records and automatically create separate lookup tables for finding records associated with the values of contained in the fields each of these recordp pthe records are instances of a class created by codenamedtuplecode which is a very memory efficient because each one lacks a codedictcode attribute that class instances normally contain using them will make it possible to access the fields of each by name using dot syntax like coderecordfieldnamecodep pthe lookup tables are codedefaultdictlistcode instances which provide dictionarylike o1 lookup times on average and also allow multiple values to be associated with each one so the lookup key is the value of the field value being sought and the data associated with it will be a list of the integer indices of the codepersoncode records stored in the codeemployeescode list with that value so theyll all be relatively smallp pnote that the code for the class is completely datadriven in that it doesnt contain any hardcoded field names which instead are all taken from the first row of csv data input file when its read in when an instance is used any actual coderetrievecode method calls must of course contain valid field name keyword argumentsp pstrongupdatestrongp pmodified to not create a lookup table for every unique value of every field when the data file is first read now the coderetrievecode method creates them only as needed and savescaches the result for future usep precodefrom collections import defaultdict namedtuple import csv class databaseobject def initself csvfilename recordname read data from csv format file into a list of namedtuples with opencsvfilename rb as inputfile csvreader csvreaderinputfile delimiter selffields csvreadernext read header row selfrecord namedtuplerecordname selffields selfrecords selfrecordrow for row in csvreader selfvalidfieldnames setselffields create an empty table of lookup tables for each field name that maps each unique field value to a list of recordlist indices of the ones that contain it selflookuptables defaultdictlambda defaultdictlist def retrieveself kwargs """ fetch a list of records with a field name with the value supplied as a keyword arg (or return none if there aren't any). """ if len(kwargs) != 1: raise valueerror( 'exactly one fieldname/keyword argument required for function ' '(%s specified)' % ', '.join([repr(k) for k in kwargs.keys()])) field, value = kwargs.items()[0] # get only keyword arg and value if field not in self.valid_fieldnames: raise valueerror('keyword arg "%s" isn\'t a valid field name' % field) if field not in self.lookup_tables: # must create field look up table for index, record in enumerate(self.records): value = getattr(record, field) self.lookup_tables[field][value].append(index) matches = [self.records[index] for index in self.lookup_tables[field].get(value, [])] return matches if matches else none if __name__ == '__main__': empdb = database('employees.csv', 'person') print "retrieve(name='ted kingston'):", empdb.retrieve(name='ted kingston') print "retrieve(age='27'):", empdb.retrieve(age='27') print "retrieve(weight='150'):", empdb.retrieve(weight='150') try: print "retrieve(hight='5ft 6in'):", empdb.retrieve(hight='5ft 6in') except valueerror as e: print "valueerror('{}') raised as expected".format(e) else: raise type('noexceptionerror', (exception,), {})( 'no exception raised from "retrieve(hight=\'5ft\')" call.') </code></pre> <p>output:</p> <pre class="lang-none prettyprint-override"><code>retrieve(name='ted kingston'): [person(name='ted kingston', age='28', weight='163', height='5ft 10in')] retrieve(age='27'): [person(name='mary manson', age='27', weight='140', height='5ft 6in'), person(name='sue sommers', age='27', weight='132', height='5ft 8in')] retrieve(weight='150'): none retrieve(hight='5ft 6in'): valueerror('keyword arg "hight" is an invalid fieldname') raised as expected </code></pre>
2
how can i obtain the models name or the content type of a django object
pyou can get the model name from the object like thisp precodeselfclassname codepre pif you prefer the content type you should be able to get that like thisp precodecontenttypeobjectsgetformodelself codepre
2
using pythons list index method on a list of tuples or objects
pyou can do this with a list comprehension and indexp precodetuplelist pineapple 5 cherry 7 kumquat 3 plum 11 x0 for x in tuplelistindexkumquat 2 x1 for x in tuplelistindex7 1 codepre
2
reading from database with sqlite and python incorrect number of binding supplied
pyou must supply a sequence of values for the binding codeidcode is a string so it looks like a sequence of 8 values p pyoure probably thinking that codeidcode should be a tuple with one element but it isnt parenthesis arent the tuplemaking syntax in python except for the empty tuple commas are use codeidcode instead to get a tuple with one element alternatively use a list codeidcodep
2
print range of numbers on same line
pcodestrjoincode would be appropriate in this casep precodegtgtgt print joinstrx for x in xrange111 1 2 3 4 5 6 7 8 9 10 codepre
2
is there any pythonic way to combine two dicts adding values for keys that appear in both
pa more generic solution which works for nonnumeric values as wellp precodea a foo bbar c baz b a spam cham x blah r dictaitems bitems k ak bk for k in setb amp seta codepre por even more genericp precodedef combinedictsa b opoperatoradd return dictaitems bitems k opak bk for k in setb amp seta codepre pfor examplep precodegtgtgt a a 2 b3 c4 gtgtgt b a 5 c6 x7 gtgtgt import operator gtgtgt print combinedictsa b operatormul a 10 x 7 c 24 b 3 codepre
2
tee does not show output or write to file
pheres a simpler way of reproducing your issuep precode cat foopy from time import sleep while true sleep2 print hello python foopy hello hello python foopy tee log no output codepre pthis happens because codepythoncode buffers stdout when its not a terminal the easiest way to unbuffer it is to use codepython ucodep precode python u foopy tee log hello hello codepre pyou can also set the shebang to codeusrbinpython ucode this does not work with codeenvcodep
2
plotting curved line in python basemap
pthis is a very old question but i thought it might be good to answer anyway when you said curved lines i assumed you meant drawing a a hrefhttpenwikipediaorgwikigreatcircle relnofollowgreat circlea there is an example of doing exactly that in the a hrefhttpmatplotlibgithubcombasemapusersexampleshtml relnofollowbasemap documentationa which i have modified to make a little more easy to modify yourselfp precodefrom mpltoolkitsbasemap import basemap import numpy as np import matplotlibpyplot as plt m basemapprojectioncyl p0ll 7398 4078 p1ll 008 5153 mdrawgreatcirclep0ll0 p0ll1 p1ll0 p1ll1 linewidth2 colorb mdrawcoastlines mfillcontinents pltshow codepre pimg srchttpistackimgurcomecvvypng altenter image description herep pnote that the great circle method cannot handle the crossing of the edges of the map a hrefhttpmatplotlibgithubcombasemapapibasemapapihtmlmpltoolkitsbasemapbasemapdrawgreatcircle relnofollowas mentioned in the documentationa which although clearly documented is a pretty major flaw imho p phope that helps somebodyp
2
python if not statement with 00
psince you are using codenonecode to signal this parameter is not set then that is exactly what you should check for using the codeiscode keywordp precodedef squarexnone if x is none print you have not entered x else yx2 return y codepre pchecking for type is cumbersome and error prone since you would have to check for emall possible input typesem not just codeintcodep
2
object class override or modify
pno pythons internals take great care to make builtin types not mutable very different design choices from rubys its not possible to make object monkeypatchable without deeply messing with the ccoded internals and recompiling the python runtime to make a very different version this is for the classic cpython but i believe exactly the same principle holds for other good implementations such as jython and ironpython just scjava and scc respectivelyp
2
moon lunar phase algorithm
pif youre like me you try to be a careful programmer so it makes you nervous when you see random code scattered across the internet that purports to solve a complex astronomical problem but doesnt explain why the solution is correctp pyou believe that there must be authoritative sources such as embooksem which contain careful and complete solutions for instancep blockquote pmeeus jean astronomical algorithms richmond willmannbell 1991 isbn 0943396352p pduffettsmith peter practical astronomy with your calculator 3rd ed cambridge cambridge university press 1981 isbn 0521284112p blockquote pyou place your trust in widelyused welltested open source libraries which can have their errors corrected unlike static web pages here then is a python solution to your question based on the a hrefhttprhodesmillorgpyephempyephema library using the a hrefhttprhodesmillorgpyephemquickhtmlphasesofthemoonphases of the moona interfacep precodeusrbinpython import datetime import ephem def getphaseondayyearmonthday returns a floatingpoint number from 01 where 0new 05full 1new ephem stores its date numbers as floating points which the following uses to conveniently extract the percent time between one new moon and the next this corresponds somewhat roughly to the phase of the moon use year month day as arguments dateephemdatedatetimedateyearmonthday nnm ephemnextnewmoon date pnm ephempreviousnewmoondate lunationdatepnmnnmpnm note that there is a ephemmoonphase command but this returns the percentage of the moon which is illuminated this is not really what we want return lunation def getmoonsinyearyear returns a list of the full and new moons in a year the list contains tuples of either the form datefull or the form datenew moons dateephemdatedatetimedateyear0101 while datedatetimeyearyear dateephemnextfullmoondate moonsappend datefull dateephemdatedatetimedateyear0101 while date.datetime().year==year: date=ephem.next_new_moon(date) moons.append( (date,'new') ) #note that previous_first_quarter_moon() and previous_last_quarter_moon() #are also methods moons.sort(key=lambda x: x[0]) return moons print get_phase_on_day(2013,1,1) print get_moons_in_year(2013) </code></pre> <p>this returns</p> <pre><code>0.632652265318 [(2013/1/11 19:43:37, 'new'), (2013/1/27 04:38:22, 'full'), (2013/2/10 07:20:06, 'new'), (2013/2/25 20:26:03, 'full'), (2013/3/11 19:51:00, 'new'), (2013/3/27 09:27:18, 'full'), (2013/4/10 09:35:17, 'new'), (2013/4/25 19:57:06, 'full'), (2013/5/10 00:28:22, 'new'), (2013/5/25 04:24:55, 'full'), (2013/6/8 15:56:19, 'new'), (2013/6/23 11:32:15, 'full'), (2013/7/8 07:14:16, 'new'), (2013/7/22 18:15:31, 'full'), (2013/8/6 21:50:40, 'new'), (2013/8/21 01:44:35, 'full'), (2013/9/5 11:36:07, 'new'), (2013/9/19 11:12:49, 'full'), (2013/10/5 00:34:31, 'new'), (2013/10/18 23:37:39, 'full'), (2013/11/3 12:49:57, 'new'), (2013/11/17 15:15:44, 'full'), (2013/12/3 00:22:22, 'new'), (2013/12/17 09:28:05, 'full'), (2014/1/1 11:14:10, 'new'), (2014/1/16 04:52:10, 'full')] </code></pre>
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queryset in view or in template
pif codeprofilegetsomestuffcode is an expensive operation and you call it multiple times in the template and yes you should call that in the view once and pass the result to the template via codecontextcodep precodedef viewrequest stuff requestuserprofilegetsomestuff return renderrequest pagehtml stuff stuff codepre palternatively you can use a hrefhttpsdocsdjangoprojectcomen18reftemplatesbuiltinswith relnofollowcode with codea tag to create a scope containing the value in its own contextp precode with stuffuserprofilegetsomestuff stuffinfo stuffotherinfo do some other things with stuff endwith codepre ppersonally i would go with the first option because with the help of codedjangodbconnectionqueriescode it is relatively easier to monitor db queries you make in the view make sure you avoid sending template querysets lazy expressions etc as much as possiblep pbtw please note that codedebugcode must be set to codetruecode for codeconnectionqueriescode to workp
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installing python imaging libary pil on ubuntu
pi had to install pythondev then install pil inside my virtualenvp pall working nowp pthanks for your help all p
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pyside pyqt mainwindow or central widget access from deeply nested widgets
pyou can always get to the current application instance via codepysideqtcoreqcoreapplicationinstancecode in c the global codeqappcode variable provides the same functionalityp pso whether you set python attributes or qt properties on the global application instance you can always get to it without having to go through any hierarchiesp
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python regex how to match a string at the end of a line in a file
pyou need to use coderesearchcode function since match tries to match the string from the beginningp precodevar1 network1 printresearchrs var1 r linegroup1 codepre pstrongexamplestrongp precodegtgtgt import re gtgtgt s foo network1 network1 gtgtgt var1 network1 gtgtgt printresearchrs var1 r sgroup1 network1 gtgtgt printresearchrs var1 r sgroup1 to check whether it fetches the last string or not 1 network1 codepre pso you should do likep precodewith openfile as f for line in f if var1 in line printresearchrs var1 r sgroup1 codepre
2
getting pyside to work with matplotlib
pi had similar goals lgpl potential commercial use and heres how i ended up getting it to workp pcreate a matplotlib widget see a hrefhttpcodegooglecomppythonxysourcebrowsesrcpythonmatplotlibqtdesignerpluginsmatplotlibwidgetpyr640d80c9867ba5f00cd0734c87da0ebd938b5d76herea for a more detailed one for pyqtp precodeimport matplotlib matplotlibuseqt4agg matplotlibrcparamsbackendqt4pyside from matplotlibfigure import figure from matplotlibbackendsbackendqt4agg import figurecanvasqtagg as figurecanvas class matplotlibwidgetfigurecanvas def initself parentnonexlabelxylabelytitletitle supermatplotlibwidget selfinitfigure selfsetparentparent selffigure figure selfcanvas figurecanvasselffigure selfaxes selffigureaddsubplot111 selfaxessetxlabelxlabel selfaxessetylabelylabel selfaxessettitletitle codepre pin qt designer i created a blank widget to hold my plot and then when i codeinitcode the main window i call setupplotp precodedef setupplotself create a matplotlib widget selfdataplot matplotlibwidget create a layout inside the blank widget and add the matplotlib widget layout qtguiqvboxlayoutselfuiwidgetplotarea layoutaddwidgetselfdataplot1 codepre pthen i call plotdatapoints as neededp precodedef plotdatapointsselfxy selfdataplotaxesclear selfdataplotaxesplotxybo selfdataplotdraw codepre pnote this clears and redraws the entire plot every time since the shape of my data keeps changing and so isnt fastp
2
how to print a string of variables without spaces in python minimal coding
ptry using codejoincodep precodeprint njoinidvar1var2var3var4 codepre por if the variables arent already stringsp precodeprint njoinmapstridvar1var2var3var4 codepre pthe benefit of this approach is that you dont have to build a long format string and it basically works unchanged for an arbitrary number of variablesp
2
calling an overridden method from base class
pyes youre missing thisp precodebbar echoes bfoo codepre pcodebcode has no codebarcode method of its own just the one inherited from codeacode codeacodes codebarcode calls codeselffoocode but in an instance of codebcode ends up calling codebcodes codefoocode and not codeacodes codefoocodep plets look at your quote againp blockquote pa method of a base class that calls another method defined in the same base class may in fact end up calling a method of a derived class that overrides itp blockquote pto translate p blockquote pcodebarcode method of codeacode the base class calls codeselffoocode but may in fact end up calling a method of the derived class that overrides it codebfoocode that overrides codeafoocodep blockquote
2
python json encoding
pi think you are simply exchanging emdumpsem and emloadsem p precodegtgtgt import json gtgtgt data apple cat banana dog pear fish codepre pthe first returns as a json encoded string its data argumentp precodegtgtgt encodedstr jsondumps data gtgtgt encodedstr apple cat banana dog pear fish codepre pthe second does the opposite returning the data corresponding to its json encoded string argumentp precodegtgtgt decodeddata jsonloads encodedstr gtgtgt decodeddata uapple ucat ubanana udog upear ufish gtgtgt decodeddata data true codepre
2
should i make my python code less foolproof to improve readability
pyour code is too emparanoidem especially when you want to protect only against yourselfp pin python circles lbyl is generally but not always frowned upon strongbutstrong theres also the often unstated assumption that one has good unit testsp pme personally i think readability is of paramount importance i mean if you emyourselfem think its hard to read what will others think and less readable code is also more likely to catch bugs not to mention making working on it hardermore time consuming you have to dig to find what the code actually emdoesem in all that lbylingp
2
deleting multiple elements from a list
pim a total beginner in python and my programming at the moment is crude and dirty to say the least but my solution was to use a combination of the basic commands i learnt in early tutorialsp precodesomelist 1234567810 rem 057 for i in rem somelisti mark for deletion for i in range0somelistcount somelistremove remove print somelist codepre pobviously because of having to choose a markfordeletion character this has its limitations p pas for the performance as the size of the list scales im sure that my solution is suboptimal however its straightforward which i hope appeals to other beginners and will work in simple cases where somelist is of a wellknown format eg always numericp
2
how do i pass a method as a parameter in python
pyes functions and methods are first class objects in python the following worksp precodedef foof print running parameter f f def bar print in bar foobar codepre poutputsp precoderunning parameter f in bar codepre pthese sorts of questions are trivial to answer using the python interpreter or for more features the a hrefhttpipythonscipyorgmoin relnofollowipythona shellp
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how to map f4 run a no name file on vim
phow about using codew cmdcode this does not require you to save before run the commandp precodemap ltf4gt w pythonltcrgt codepre paccording to vim codehelp wccodep blockquote pcoderangewrite opt cmdcodep precode execute cmd with range lines as standard input note the space in front of the cmd is executed like with cmd any is replaced with the previous command codepre blockquote pstrongnotestrong this will not work as expected if the python program itself use filename for example codefilecode will yield codeltstdingtcodep
2
python operator
pcodegtgtcode and codeltltcode are the strongrightshiftstrong and strongleftshiftstrong bitoperators ie they alter the binary representation of the number it can be used on other data structures as well but python doesnt implement that they are defined for a class by codershiftself shiftcode and codelshiftself shiftcodep pstrongexamplestrongp precodegtgtgt bin10 10 in binary 1010 gtgtgt 10 gtgt 1 shifting all the bits to the right and discarding the rightmost one 5 gtgtgt bin 5 in binary you can see the transformation clearly now 0101 gtgtgt 10 gtgt 2 shifting all the bits right by two and discarding the tworightmost ones 2 gtgtgt bin 0010 codepre pstrongshortcutstrong just to perform an integer division ie discard the remainder in python youd implement it as codecode on a number by 2 raised to the number of bits you were shiftingp precodegtgtgt def rshiftno shift 1 return no 2shift this func will now be equivalent to gtgt operator codepre
2
getting deprecation warning in sklearn over 1d array despite not having a 1d array
pthe error is coming from the predict method numpy will interpret 11 as a 1d array so this should avoid the warningp pcodeclfpredictnparray11codep pnotice thatp precodein 14 p1 nparray11 in 15 p1shape out15 2 in 16 p2 nparray11 in 17 p2shape out17 1 2 codepre palso note that you cant use an array of shape 21p precodein 21 p3 nparray11 in 22 p3shape out22 2 1 in 23 clfpredictp3 valueerror traceback most recent call last ltipythoninput23e4070c037d78gt in ltmodulegt gt 1 clfpredictp3 homejuananaconda3libpython35sitepackagessklearnsvmbasepy in predictself x 566 class labels for samples in x 567 gt 568 y superbasesvc, self).predict(x) 569 return self.classes_.take(np.asarray(y, dtype=np.intp)) 570 /home/juan/anaconda3/lib/python3.5/site-packages/sklearn/svm/base.py in predict(self, x) 303 y_pred : array, shape (n_samples,) 304 """ --&gt; 305 x = self._validate_for_predict(x) 306 predict = self._sparse_predict if self._sparse else self._dense_predict 307 return predict(x) /home/juan/anaconda3/lib/python3.5/site-packages/sklearn/svm/base.py in _validate_for_predict(self, x) 472 raise valueerror("x.shape[1] = %d should be equal to %d, " 473 "the number of features at training time" % --&gt; 474 (n_features, self.shape_fit_[1])) 475 return x 476 valueerror: x.shape[1] = 1 should be equal to 2, the number of features at training time </code></pre>
2
python list concatenation with strings into new list
puse string concatenation in a list comprehensionp precodegtgtgt list1 item1 item2 item3 item4 gtgtgt string example gtgtgt x string for x in list1 item1example item2example item3example item4example codepre
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if python doesnt support method overloading then why does this method overload work while this other does not
pyou arent overloading youre hiding one thing behind another by using the same name for different objects tryp precodesum 42 codepre pand see how codeprintsum3 5code ceases to workp
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not getting exact result in python with the values leading zero please tell me what is going on there
pin python 2x number with a leading zero is interpreted as octal baseeight python 3x requires a leading 0o to indicate an octal number you probably want to treat a zipcode as a string to keep the leading zeroes intactp
2