Mandatory Default variables and parameter propagation while changing signature (refactoring) in pycharm

Question

I'm doing an evaluation of pycharm and is stuck with the refactoring bit. What I want to achieve is to add a new parameter in one of the functions. I have two problems here.

1. Whenever I add a new parameter, it says 'Default Value is missing'
2. Propagate Parameters seems disabled all the time

So, is default value mandatory? and how would I reflect the new parameter in all function calls?

Attaching a screenshot if that helps..

Answer 1

It appears that "Default value" is not supposed to mean "default value" in the Python sense: it is the text to be put in calls that will be changed according to the new signature, these necessarily defaulting on the extended signature.

This would also explain the additional checkbox for actually putting that value as a "Python default value" with the new parameter. It is then shown as a Python default value (= ...) in the signature preview.

Thus, if you place the text thing2 in the box for "Default value" for new_param, and leave the checkbox unchecked, then after refactoring (which is then possible)

fn1(thing1)

becomes

fn1(thing1, thing2)

at the call site, and the refactored definition of fn1 then becomes

def fn1(param1, new_param):
    #  ...

That is, no Python default values are involved.