Programmatically get function arguments (without **kwargs)?

Question

Given the following function:

def test(* p1=None, p2=None):
  ...

Called as follows:

test(p2="hello")

Can I programmatically obtain a list/dictionary of the arguments and their value at runtime?

1: Don't want to use **kwargs because I want to force the user to use the proper argument names (and plan to do type annotation as well).

2: I've looked at the inspect module for getting the defaults, but does not seem to let me see the run-time values.

Looking to create code something like this:

request = {k: v for k,v in __some_magic_location__ if v is not None}

So, in that case, would you want an output of `{"p2": "hello"}` or `{"p1": None, "p2": "hello"}?` — internet_user, Jan 24 '18 at 16:26
A pity it's closed now, but I don't want to un-dupe-hammer it open, either. Just wanted to suggest using a decorator `def deco(f): def _f(**kwargs): print("PARAMS:", kwargs) return f(**kwargs) return _f` and then `@deco def test(...)`; this way, you can use `kwargs` to print the arguments, and at the same time prevent the user from passing invalid keyword-arguments or arguments without a name. — tobias_k, Jan 24 '18 at 16:34

Vincent · Accepted Answer · 2018-01-24T16:23:01.633

4

>>> def test(*, p1=None, p2=None):
...     return locals()
...
>>> test(p2='hello')
{'p1': None, 'p2': 'hello'}

edited Jan 24 '18 at 16:23

answered Jan 24 '18 at 16:22

Vincent

1

I think it is safe to assume that OP **cannot** change `test` – Ma0 Jan 24 '18 at 16:22
@Ev.Kounis The OP said they "don't want to use **kwargs", so I think this is exactly what they want. – Aran-Fey Jan 24 '18 at 16:25
@Rawing You have a point there. This problem just seems too trivial in this case. – Ma0 Jan 24 '18 at 16:25
What is the `*` for? – mrCarnivore Jan 24 '18 at 16:30
Yes, I can change test. Had just never run across 'locals' before. The "*" is a Python3 syntax indicating that all the arguments after it need to be passed by name, not position. – rgacote Jan 25 '18 at 17:38
Also, if you use locals() within a class method, you need to filter out the 'self' entry. – rgacote Jan 25 '18 at 19:05

Ajax1234 · Answer 2 · 2018-01-24T17:48:29.350

1

You can use inspect.getcallargs:

import inspect
def test(*, p1=None, p2=None):
  pass

print(inspect.getcallargs(test, p2 = 'Hello'))

Output:

{'p2': 'Hello', 'p1': None}

edited Jan 24 '18 at 17:48

answered Jan 24 '18 at 16:21

Ajax1234

2 Answers2