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"""This is version 0.7 of Philip J. Eby's simplegeneric module

(http://pypi.python.org/pypi/simplegeneric), patched to work with Python 3,

which doesn't support old-style classes.

"""

#Name: simplegeneric

#Version: 0.7

#Summary: Simple generic functions (similar to Python's own len(), pickle.dump(), etc.)

#Home-page: http://pypi.python.org/pypi/simplegeneric

#Author: Phillip J. Eby

#Author-email: peak@eby-sarna.com

#License: PSF or ZPL

__all__ = ["generic"]

try:

from types import ClassType, InstanceType

except ImportError:

classtypes = type

else:

classtypes = type, ClassType

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}

try:

_by_type[InstanceType] = _by_class

except NameError: # Python 3

pass

_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,

)