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class Pipeline(object): |
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"""Defines a pipeline for transforming sequence data. |
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The input is assumed to be utf-8 encoded `str` (Python 3) or |
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`unicode` (Python 2). |
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Attributes: |
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convert_token: The function to apply to input sequence data. |
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pipes: The Pipelines that will be applied to input sequence |
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data in order. |
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""" |
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def __init__(self, convert_token=None): |
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"""Create a pipeline. |
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Arguments: |
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convert_token: The function to apply to input sequence data. |
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If None, the identity function is used. Default: None |
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""" |
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if convert_token is None: |
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self.convert_token = Pipeline.identity |
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elif callable(convert_token): |
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self.convert_token = convert_token |
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else: |
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raise ValueError("Pipeline input convert_token {} is not None " |
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"or callable".format(convert_token)) |
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self.pipes = [self] |
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def __call__(self, x, *args): |
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"""Apply the the current Pipeline(s) to an input. |
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Arguments: |
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x: The input to process with the Pipeline(s). |
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Positional arguments: Forwarded to the `call` function |
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of the Pipeline(s). |
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""" |
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for pipe in self.pipes: |
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x = pipe.call(x, *args) |
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return x |
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def call(self, x, *args): |
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"""Apply _only_ the convert_token function of the current pipeline |
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to the input. If the input is a list, a list with the results of |
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applying the `convert_token` function to all input elements is |
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returned. |
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Arguments: |
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x: The input to apply the convert_token function to. |
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Positional arguments: Forwarded to the `convert_token` function |
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of the current Pipeline. |
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""" |
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if isinstance(x, list): |
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return [self.convert_token(tok, *args) for tok in x] |
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return self.convert_token(x, *args) |
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def add_before(self, pipeline): |
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"""Add a Pipeline to be applied before this processing pipeline. |
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Arguments: |
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pipeline: The Pipeline or callable to apply before this |
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Pipeline. |
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""" |
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if not isinstance(pipeline, Pipeline): |
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pipeline = Pipeline(pipeline) |
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self.pipes = pipeline.pipes[:] + self.pipes[:] |
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return self |
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def add_after(self, pipeline): |
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"""Add a Pipeline to be applied after this processing pipeline. |
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Arguments: |
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pipeline: The Pipeline or callable to apply after this |
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Pipeline. |
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""" |
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if not isinstance(pipeline, Pipeline): |
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pipeline = Pipeline(pipeline) |
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self.pipes = self.pipes[:] + pipeline.pipes[:] |
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return self |
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@staticmethod |
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def identity(x): |
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"""Return a copy of the input. |
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This is here for serialization compatibility with pickle. |
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""" |
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return x |
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