How to introspect a function defined in a Cython C extension module

I've retracted my duplicate suggestion (saying that it was impossible...) having investigated further. It seems to work fine with reasonably recent versions of Cython (v0.23.4) and Python 3.4.4.

import cython
import inspect
scope = cython.inline("""def f(a,*args,b=False): pass """)
print(inspect.getfullargspec(scope['f']))

gives the output

FullArgSpec(args=['a'], varargs='args', varkw=None, defaults=None, kwonlyargs=['b'], kwonlydefaults={'b': False}, annotations={})

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Also mentioned in the documentation is the compilation option "binding" which apparently makes this detail more accessible (although I didn't need it).

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I have a feeling that this may depend on improvements to inspect made relatively recently (possibly this fix) so if you're using Python 2 you're probably out of luck.

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Edit: your example works if you using the binding compilation option:

import cython
@cython.binding(True)
def example(a, b=None):                                                                                                                                                       
    pass

I suspect that inline adds it automatically (but the code to do inline is sufficiently convoluted that I can't find proof of that either way). You can also set it as a file-level option.