Python getargspec, getfullargspec, Signature performance comparison

gistfile1.txt

# So interestingly, Signature seems to be twice as fast in Python 3.6 and 3.7 as it 
# was in Python 3.3 and 3.4.  However, it is still 6-18 times slower than the old
# getargspec or getfullargspec that was in Python 3.3.

Python 2.7 getargspec (doesn't use Signature)         : specimen_one (6 args)   : 0.0503
Python 2.7 getargspec (doesn't use Signature)         : specimen_two (0 args)   : 0.0496
Python 2.7 getargspec (doesn't use Signature)         : specimen_three (6 args) : 0.0500
Python 2.7 getargspec (doesn't use Signature)         : specimen_four (13 args) : 0.0652

Python 3.3 getfullargspec (doesn't use Signature)     : specimen_one (6 args)   : 0.0539
Python 3.3 getfullargspec (doesn't use Signature)     : specimen_two (0 args)   : 0.0590
Python 3.3 getfullargspec (doesn't use Signature)     : specimen_three (6 args) : 0.0596
Python 3.3 getfullargspec (doesn't use Signature)     : specimen_four (13 args) : 0.0568

Python 3.3 signature                                  : specimen_one (6 args)   : 0.6158
Python 3.3 signature                                  : specimen_two (0 args)   : 0.2562
Python 3.3 signature                                  : specimen_three (6 args) : 0.4190
Python 3.3 signature                                  : specimen_four (13 args) : 0.8836

Python 3.4 signature                                  : specimen_one (6 args)   : 0.5991
Python 3.4 signature                                  : specimen_two (0 args)   : 0.2798
Python 3.4 signature                                  : specimen_three (6 args) : 0.4509
Python 3.4 signature                                  : specimen_four (13 args) : 0.8818

Python 3.6 signature                                  : specimen_one (6 args)   : 0.3167
Python 3.6 signature                                  : specimen_two (0 args)   : 0.1298
Python 3.6 signature                                  : specimen_three (6 args) : 0.2366
Python 3.6 signature                                  : specimen_four (13 args) : 0.5633

Python 3.7 signature                                  : specimen_one (6 args)   : 0.2447
Python 3.7 signature                                  : specimen_two (0 args)   : 0.1301
Python 3.7 signature                                  : specimen_three (6 args) : 0.1784
Python 3.7 signature                                  : specimen_four (13 args) : 0.4597

Python 3.4 getfullargspec (uses Signature internally) : specimen_one (6 args)   : 0.7807
Python 3.4 getfullargspec (uses Signature internally) : specimen_two (0 args)   : 0.3409
Python 3.4 getfullargspec (uses Signature internally) : specimen_three (6 args) : 0.5325
Python 3.4 getfullargspec (uses Signature internally) : specimen_four (13 args) : 1.2213

Python 3.6 getfullargspec (uses Signature internally) : specimen_one (6 args)   : 0.3634
Python 3.6 getfullargspec (uses Signature internally) : specimen_two (0 args)   : 0.1247
Python 3.6 getfullargspec (uses Signature internally) : specimen_three (6 args) : 0.2484
Python 3.6 getfullargspec (uses Signature internally) : specimen_four (13 args) : 0.6777

Python 3.7 getfullargspec (uses Signature internally) : specimen_one (6 args)   : 0.3142
Python 3.7 getfullargspec (uses Signature internally) : specimen_two (0 args)   : 0.1060
Python 3.7 getfullargspec (uses Signature internally) : specimen_three (6 args) : 0.2232
Python 3.7 getfullargspec (uses Signature internally) : specimen_four (13 args) : 0.5562

test.py

from __future__ import print_function


def specimens():
    def specimen_one(a, b, c=10, d=15):
        pass

    def specimen_two():
        pass

    def specimen_three(*args, **kw):
        pass

    def specimen_four(
        argument_one,
        argument_two,
        argument_three,
        argument_four,
        argument_five,
        argument_six,
        argument_seven,
        argument_eight=None,
        argument_nine=None,
        argument_ten=None,
    ):
        pass

    return specimen_one, specimen_two, specimen_three, specimen_four


import inspect
import sys
import timeit


def tests():
    try:
        yield inspect.getfullargspec
    except AttributeError:
        yield inspect.getargspec

    try:
        yield inspect.signature
    except AttributeError:
        pass


def run_tests():
    global spec
    global test

    for test in tests():
        for spec in specimens():

            time = timeit.timeit(
                "test(spec)", "from __main__ import spec, test", number=10000
            )

            argspec = inspect.getargspec(spec)

            header = "Python %s %s%s" % (
                ".".join(str(x) for x in sys.version_info[0:2]),
                test.__name__,
                " (uses Signature internally)"
                if sys.version_info >= (3, 4)
                and test.__name__ == "getfullargspec"
                else " (doesn't use Signature)"
                if test.__name__ in ("getfullargspec", "getargspec")
                else "",
            )
            header += " " * (54 - len(header))

            header = "%s: %s (%s args)" % (
                header,
                spec.__name__,
                sum(
                    len(element) if element is not None else 0
                    for element in argspec
                ),
            )

            header += " " * (80 - len(header))
            print(
                "%s: %.4f"
                % (
                    header,
                    time,
                )
            )
        print("\n")


if __name__ == "__main__":
    run_tests()