Revert to default function argument value when passing from dict with missing key

Question

Suppose I have a function with a default argument value set in the definition, like this:

def foo(a=1):
    print(a)

The input data comes from a dictionary which sometimes does or doesn't have the key. I want to have the default value set when the key is not present in the dictionary I am querying. So far I tried to solve it using the .get function, but that's not working as expected because it returns None if the key is missing:

dictionary_a={a:10, b: 100, c: 42}

dictionary_b={b: 100, c: 42}


foo(dictionary_a.get("a"))

> 10

foo(dictionary_b.get("a"))

> None

Querying it like dictionary["a"] also doesn't work because if the key is missing there is an error. How can I make this work as intended?

Answer 1

Try setting all default parameters to None and change it inside the function.

def foo(a=None, b=None):
   if a is None:
     a = 1
   if b is None:
     b = 2