[Python-ideas] Add "default" kwarg to list.pop()

[Steven D'Aprano]

On Thu, Nov 01, 2018 at 09:36:19PM +0200, Serhiy Storchaka wrote:
> 31.10.18 13:07, Antoine Pitrou пише:
> >l.pop(default=...) has the potential to be multi-thread-safe, while
> >your alternatives haven't.
> 
> The multi-thread-safe alternative is:
> 
>     try:
>         value = l.pop()
>     except IndexError:
>         value = default

That's not an expression, so there are limits to where and when you can 
use it. What we need is a helper function that wraps that, called "pop". 
And since this seems to be reoccuring request going back nearly 20 years 
now:

https://mail.python.org/pipermail/python-dev/1999-July/000550.html
https://stackoverflow.com/questions/31216428/python-pop-from-empty-list

as is the more general get(list, index, default=None) helper:

https://stackoverflow.com/questions/2574636/getting-a-default-value-on-index-out-of-range-in-python
https://stackoverflow.com/questions/2492087/how-to-get-the-nth-element-of-a-python-list-or-a-default-if-not-available
https://stackoverflow.com/questions/5125619/why-doesnt-list-have-safe-get-method-like-dictionary
https://stackoverflow.com/questions/17721748/default-value-for-out-of-bounds-list-index

we could save people from having to re-invent the wheel over and over 
again by add them to a new module called 
"things_that_should_be_list_methods_but_arent.py" 

*wink*



-- 
Steve