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