Python C extension: method signatures for documentation?

Question

I am writing C extensions, and I\'d like to make the signature of my methods visible for introspection.

static PyObject* foo(PyObject *self, PyObject *args)          


        

Answer 1

My usual approach to finding out about things like this is: "use the source".

Basically, I would presume that the standard modules of python would use such a feature when available. Looking at the source (for example here) should help, but in fact even the standard modules add the prototype after the automatic output. Like this:

torsten@pulsar:~$ python2.6
>>> import fcntl
>>> help(fcntl.flock)
flock(...)
    flock(fd, operation)

    Perform the lock operation op on file descriptor fd.  See the Unix [...]

So as upstream is not using such a feature, I would assume it is not there. :-)

Okay, I just checked current python3k sources and this is still the case. That signature is generated in pydoc.py in the python sources here: pydoc.py. Relevant excerpt starting in line 1260:

        if inspect.isfunction(object):
            args, varargs, varkw, defaults = inspect.getargspec(object)
            ...
        else:
            argspec = '(...)'

inspect.isfunction checks if the object the documentation is requested for is a Python function. But C implemented functions are considered builtins, therefore you will always get name(...) as the output.