mike bayer added the comment:
we basically need to be able to get the argument signature for anything that
passes callable(); function, method, class, object with __call__. So this is
the logic we use:
import inspect
def get_callable_argspec(fn):
if inspect.isfunction(fn) or inspect.ismethod(fn):
inspectable = fn
elif inspect.isclass(fn):
inspectable = fn.__init__
elif hasattr(fn, '__call__'):
inspectable = fn.__call__
else:
inspectable = fn
try:
return inspect.getargspec(inspectable)
except TypeError:
raise
def callable1(self, x, y):
pass
class SomeClass(object):
def __init__(self, x, y):
pass
def callable2(self, x, y):
pass
def __call__(self, x, y):
pass
callable3 = SomeClass
callable4 = SomeClass(2, 3)
for callable_ in (callable1, SomeClass(1, 2).callable2, callable3, callable4):
assert callable(callable_) # the interpreter can tell me this
# how can it reliably tell me this?
assert get_callable_argspec(callable_) == (["self", "x", "y"], None, None,
None)
If you pass a builtin like datetime.datetime.today to it,
isfunction()/ismethod()/isclass() return false, but it does have a __call__().
I'm working around this now by just refusing to act on anything that is
types.BuiltinMethodType or types.BuiltinFunctionType.
Any guidance on what the proper way is to get the argument signature for any
object that returns True for callable() would be very helpful (py2.6-3.x
compatible). I'm not sure if there's a stdlib call for this.
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<http://bugs.python.org/issue20828>
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