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""" |
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ETLT |
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Copyright 2016 Set Based IT Consultancy |
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Licence MIT |
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""" |
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import re |
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from etlt.condition.FalseCondition import FalseCondition |
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from etlt.condition.GlobCondition import GlobCondition |
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from etlt.condition.PlainCondition import PlainCondition |
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from etlt.condition.RegularExpressionCondition import RegularExpressionCondition |
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from etlt.condition.TrueCondition import TrueCondition |
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class SimpleConditionFactory: |
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""" |
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A factory for simple conditions. |
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""" |
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_constructors = {} |
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""" |
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A map from scheme to object constructors. |
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dict[str, callable] |
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""" |
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# ------------------------------------------------------------------------------------------------------------------ |
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@staticmethod |
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def _split_scheme(expression): |
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""" |
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Splits the scheme and actual expression |
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:param str expression: The expression. |
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:rtype: str |
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""" |
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match = re.search(r'^([a-z]+):(.*)$', expression) |
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if not match: |
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scheme = 'plain' |
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actual = expression |
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else: |
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scheme = match.group(1) |
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actual = match.group(2) |
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return scheme, actual |
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# ------------------------------------------------------------------------------------------------------------------ |
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@staticmethod |
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def register_scheme(scheme, constructor): |
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""" |
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Registers a scheme. |
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:param str scheme: The scheme. |
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:param callable constructor: The SimpleCondition constructor. |
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""" |
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if not re.search(r'^[a-z]+$', scheme): |
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raise ValueError('{0!s} is not a valid scheme'.format(scheme)) |
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if scheme in SimpleConditionFactory._constructors: |
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raise ValueError('Scheme {0!s} is registered already'.format(scheme)) |
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SimpleConditionFactory._constructors[scheme] = constructor |
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# ------------------------------------------------------------------------------------------------------------------ |
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@staticmethod |
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def create_condition(field, expression): |
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""" |
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:param str field: The name of the field. |
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:param expression: The expression (including scheme). |
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:rtype: gdwh.map.SimpleCondition.SimpleCondition |
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""" |
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scheme, expression = SimpleConditionFactory._split_scheme(expression) |
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if scheme not in SimpleConditionFactory._constructors: |
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raise ValueError('Scheme {0!s} is not registered'.format(scheme)) |
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return SimpleConditionFactory._constructors[scheme](field, expression) |
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# ---------------------------------------------------------------------------------------------------------------------- |
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SimpleConditionFactory.register_scheme('false', FalseCondition) |
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SimpleConditionFactory.register_scheme('glob', GlobCondition) |
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SimpleConditionFactory.register_scheme('plain', PlainCondition) |
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SimpleConditionFactory.register_scheme('re', RegularExpressionCondition) |
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SimpleConditionFactory.register_scheme('true', TrueCondition) |
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PyETLT /
etlt
