PEP 671 Syntax for late bound function default values

[stevendaprano]

PEP 671 proposes to introduce syntax to solve the "early binding gotcha" when mutable objects are used as default arguments. Instead of writing

def func(arg=None):
    if arg is None:
        arg = []

one could instead use the special syntax arg=>[] in the function signature.

The author of the PEP is looking for support for the proposal. Who likes the idea of having a way to set late-bound defaults in the function signature is this way?

For those who are unsure of the difference between early and late binding in this context, it is this:

• Default values in Python currently are evaluated once, when the function is created, and then re-used when needed. (Early-binding.)
  
• This PEP proposes to add a second mechanism, which re-evaluates the default expression each time the default value is needed. (Late-binding.)
  

For anyone who wants to read the background, there are a couple of long discussions on this topic in the Python-Ideas mailing list, starting last year and continuing here with some pauses in between.

[Gribouillis]

It is a good idea. It is frequent to have the structure

if arg is sentinel:
    arg = some_value

The pep would make better and cleaner code. +1

*Pronouns: he/him **(why is my pronoun here?)*

This is so ridiculous. Why does GvR add this to his signature in discussions? Or perhaps it is politically correct must for people working for Microsoft?

[DeaD_EyE]

I thought it's already in Python 3.11, but it's still a draft.

This change can help to clean up the existing code bases. I like the idea because it's directly visible in the function signature, and you don't have to look in the code of the function. The old way to archive this, is a bit verbose.

This is so ridiculous. Why does GvR add this to his signature in discussions? Or perhaps it is politically correct must for people working for Microsoft?

He is a part of BigTech, which is a part of Transhumanism (Eugenics).
Google: Yuval Noah Harari