Yesterday I was attending a conference about a MOCK like library and the speaker told us about some "inspect" functionalities not working correctly with builtins. For instance:
"""
Python 3.3.0 (default, Oct 2 2012, 02:07:16)
[GCC 4.4.3] on linux
Type "help", "copyright", "credits" or "license" for more information.
>>> import inspect
>>> def f(a=None) :
... pass
...
>>> inspect.getcallargs(f)
{'a': None}
>>> inspect.getargspec(f)
ArgSpec(args=['a'], varargs=None, keywords=None, defaults=(None,))
>>> inspect.getcallargs(list)
Traceback (most recent call last):
File "<stdin>", line 1, in <module>
File "/usr/local/lib/python3.3/inspect.py", line 993, in getcallargs
spec = getfullargspec(func)
File "/usr/local/lib/python3.3/inspect.py", line 850, in getfullargspec
raise TypeError('{!r} is not a Python function'.format(func))
TypeError: <class 'list'> is not a Python function
>>> inspect.getargspec(list)
Traceback (most recent call last):
File "<stdin>", line 1, in <module>
File "/usr/local/lib/python3.3/inspect.py", line 823, in getargspec
getfullargspec(func)
File "/usr/local/lib/python3.3/inspect.py", line 850, in getfullargspec
raise TypeError('{!r} is not a Python function'.format(func))
TypeError: <class 'list'> is not a Python function
>>>
"""
Can we annotate builtins to support this?. What about types defined in CModules?
I am fully aware that the interpreter doesn't know how a method/function written in C is going to parse the parameter list/keywords. And that even if we solve this (for instance, with annotations that create wrappers calling "PyArg_Parse()" automatically), every C extension out there would need to support it too.
Just brainstorming.
So at this point you should use inspect.signature(), not getfullargspec().
With that you could do this if you either allowed setting the __signature__ attribute and then provided code that would set it, made __signature__ a property that returned the Signature object if desired on a built-in, or come up with some automated way to take the argument string from PyArg_Parse() as you suggested.