this post was submitted on 22 Jul 2025
17 points (100.0% liked)

Python

7340 readers
47 users here now

Welcome to the Python community on the programming.dev Lemmy instance!

πŸ“… Events

PastNovember 2023

October 2023

July 2023

August 2023

September 2023

🐍 Python project:
πŸ’“ Python Community:
✨ Python Ecosystem:
🌌 Fediverse
Communities
Projects
Feeds

founded 2 years ago
MODERATORS
erlingur@programming.dev
jnovinger@programming.dev
norambna@programming.dev
17
Avoiding boilerplate by using immutable default arguments (vulwsztyn.codeberg.page)
submitted 1 week ago by Vulwsztyn@programming.dev to c/python@programming.dev
8 comments fedilink hide all child comments
 

Hi, I recently realised one can use immutable default arguments to avoid a chain of:

def append_to(element, to=None):
    if to is None:
        to = []

at the beginning of each function with default argument for set, list, or dict.

you are viewing a single comment's thread
view the rest of the comments
[–] Narann@jlai.lu 4 points 1 week ago (7 children)

This is the way you're supposed to write it in Python.

It is something you get used to, yet I think it's sad.

[–] m_f@discuss.online 5 points 1 week ago (5 children)

You can use mutable default arguments now with a new syntax:

https://peps.python.org/pep-0671/

def bisect_right(a, x, lo=0, hi=>len(a), *, key=None):
def connect(timeout=>default_timeout):
def add_item(item, target=>[]):
def format_time(fmt, time_t=>time.time()):
[–] Narann@jlai.lu 2 points 1 week ago (1 children)

Does not seems to work on 3.12:

Python 3.12.11 (main, Jun 29 2025, 16:18:35) [MSC v.1944 64 bit (AMD64)] on win32
>>> def toto(tata=>[]):
  File "<stdin>", line 1
    def toto(tata=>[]):
                  ^
SyntaxError: invalid syntax
[–] logging_strict@programming.dev 1 points 1 week ago* (last edited 1 week ago)

Upvote for the sanity check.

As the OP mentioned, this is a proposed/draft feature that may or may not ever happen.

With these kinda posts, should start a betting pool. To put money down on whether this feature sees the light of day within an agreed upon fixed time frame.

load more comments (3 replies)
load more comments (4 replies)