Well we don't actually need inspect here.

>>> func = lambda x, y: (x, y)
>>> 
>>> func.__code__.co_argcount
2
>>> func.__code__.co_varnames
('x', 'y')
>>>
>>> def func2(x,y=3):
...  print(func2.__code__.co_varnames)
...  pass # Other things
... 
>>> func2(3,3)
('x', 'y')
>>> 
>>> func2.__defaults__
(3,)

Essentially, I'm trying to work out how to, from within a function, get a completely populated *args and **kwargs, including the function's named parameters.

How about saving the arguments via locals() at the beginning of the function?

def my_func(a, *args, **kwargs):
    saved_args = {**locals()}  # Updated to make a copy per loco.loop
    print("saved_args is", saved_args)
    local_var = 10
    print("saved_args is", saved_args)
    print("But locals() is now", locals())
    
my_func(20, 30, 40, 50, kwarg1='spam', kwarg2='eggs')

It gives this output:

saved_args is {'a': 20, 'args': (30, 40, 50), 'kwargs': {'kwarg1': u'spam', 'kwarg2': u'eggs'}}
saved_args is {'a': 20, 'args': (30, 40, 50), 'kwargs': {'kwarg1': u'spam', 'kwarg2': u'eggs'}}
But locals is now {'a': 20, 'saved_args': {...}, 'args': (30, 40, 50), 'local_var': 10, 'kwargs': {'kwarg1': u'spam', 'kwarg2': u'eggs'}}

Hat tip: https://stackoverflow.com/a/3137022/2829764

This is the best way to have it in order, a list of tuples:

>>> import inspect
>>> def name_and_args():
...     caller = inspect.stack()[1][0]
...     args, _, _, values = inspect.getargvalues(caller)
...     return [(i, values[i]) for i in args]
... 

>>> def f(a, b, c):
...     print(name_and_args())
...

>>> f(1, 2, 3)
[('a', 1), ('b', 2), ('c', 3)]

So just call the name_and_args function in every function as we have in f.

Here's a simple implementation:

from functools import wraps

def prints_invocation(f):
    @wraps(f)
    def wrapped(*args):
        print "%s(%s)" % (f.__name__, ', '.join(repr(a) for a in args))
        return f(*args)
    return wrapped

>>> @prints_invocation
... def add(x, y):
...     return x + y
>>> add(1, 2)
add(1, 2)
3

It would be fairly trivial to extend this to print kwargs and return values