108 lines
3.0 KiB
Python
108 lines
3.0 KiB
Python
import inspect
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__all__ = ["generic"]
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try:
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from types import ClassType, InstanceType
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classtypes = type, ClassType
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except ImportError:
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classtypes = type
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InstanceType = None
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def generic(func, argpos=None):
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"""Create a simple generic function"""
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if argpos is None:
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if hasattr(func, 'argpos'):
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argpos = func.argpos
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else:
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argnames = inspect.getargspec(func)[0]
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if argnames and argnames[0] == 'self':
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argpos = 1
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else:
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argpos = 0
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_sentinel = object()
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def _by_class(*args, **kw):
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cls = args[argpos].__class__
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for t in type(cls.__name__, (cls, object), {}).__mro__:
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f = _gbt(t, _sentinel)
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if f is not _sentinel:
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return f(*args, **kw)
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else:
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return func(*args, **kw)
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_by_type = {object: func, InstanceType: _by_class}
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_gbt = _by_type.get
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def when_type(*types):
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"""Decorator to add a method that will be called for the given types"""
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for t in types:
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if not isinstance(t, classtypes):
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raise TypeError(
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"%r is not a type or class" % (t,)
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)
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def decorate(f):
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for t in types:
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if _by_type.setdefault(t, f) is not f:
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raise TypeError(
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"%r already has method for type %r" % (func, t)
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)
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return f
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return decorate
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_by_object = {}
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_gbo = _by_object.get
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def when_object(*obs):
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"""Decorator to add a method to be called for the given object(s)"""
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def decorate(f):
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for o in obs:
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if _by_object.setdefault(id(o), (o, f))[1] is not f:
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raise TypeError(
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"%r already has method for object %r" % (func, o)
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)
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return f
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return decorate
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def dispatch(*args, **kw):
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f = _gbo(id(args[argpos]), _sentinel)
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if f is _sentinel:
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for t in type(args[argpos]).__mro__:
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f = _gbt(t, _sentinel)
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if f is not _sentinel:
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return f(*args, **kw)
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else:
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return func(*args, **kw)
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else:
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return f[1](*args, **kw)
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dispatch.__name__ = func.__name__
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dispatch.__dict__ = func.__dict__.copy()
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dispatch.__doc__ = func.__doc__
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dispatch.__module__ = func.__module__
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dispatch.when_type = when_type
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dispatch.when_object = when_object
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dispatch.default = func
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dispatch.has_object = lambda o: id(o) in _by_object
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dispatch.has_type = lambda t: t in _by_type
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dispatch.argpos = argpos
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return dispatch
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def test_suite():
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import doctest
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return doctest.DocFileSuite(
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'README.txt',
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optionflags=doctest.ELLIPSIS | doctest.REPORT_ONLY_FIRST_FAILURE,
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)
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if __name__ == '__main__':
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import unittest
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r = unittest.TextTestRunner()
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r.run(test_suite())
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