Question

following this topic: allow users to "extend" API functions

class Inspector:
    def __init__(self, passedFunc):
        self.passedFunc = passedFunc

    def __call__(self, *args, **kwargs):
        # Inspector needs to generate a list of arguments of the passed function and print them in *correct* order

        # now how to generate a list of arguments using data from both ''args' and 'kwargs'?
        # the user might keep default argument values, in which case both will be None,
        # he might only use args, in which case it is easy,
        # but he might also use kwargs, in which case I don't see how to generate a list with correct order of arguments
        # and he might use all 3 from above together

        # I found this solution for when only default arguments are used
        if args == () and kwargs == {}: args = self.passedFunc.__defaults__

        print args  

@Inspector
def exampleFunc(value=0, otherValue=3):
    pass

exampleFunc()

How to generate a correct order args list for all scenarios?

Answer 1

This is how you can build the actual parameters list in the decorator:

import inspect

class Inspector:
    def __init__(self, passedFunc):
        self.passedFunc = passedFunc

    def __call__(self, *args, **kwargs):

        spec = inspect.getargspec(self.passedFunc)
        params = dict(zip(spec.args, args))
        defaults = dict(zip(spec.args[-len(spec.defaults):], spec.defaults))

        for k, v in kwargs.items():
            if k not in spec.args:
                raise TypeError('unexpected argument', k)
            if k in params:
                raise TypeError('mulitple values for argument', k)
            params[k] = v

        for k in spec.args:
            if k not in params:
                if k in defaults:
                    params[k] = defaults[k]
                else:
                    raise TypeError('missing argument', k)

        args_in_order = [params[x] for x in spec.args]

        print args_in_order

Example:

@Inspector
def exampleFunc(value=0, otherValue=3):
    pass

exampleFunc()  # 0,3
exampleFunc('foo')  # foo,3
exampleFunc(otherValue='foo', value=555) # 555,foo