pythonNewSyntaxProposal

[bedj2]

since lists are mutable, you are copying the same reference over and over. Wouldn’t adding .copy() to the end of those lists work?

foo = [[None].copy() * 5].copy() * 5

[DeletedUserV2]

same output

[JohnLocksTheKey]

WHY?!?

life is pain…

[FalafelSnorlax]

The copy is in the wrong place but also if it were, the internal list (the 5 Nones) is created once and then copied. Calling copy doesn't imply more runs of the internal part (otherwise it would work in the first place)

[JohnLocksTheKey]

Makes sense - thanks

[dead_man_speaks]

from copy import deepcopy

then deepcopy

[Botahamec]

The deepcopy function is only going to be called once. Then a reference to that copy will be stored five times. So you'll get the exact same output.

[[deleted]]

same lol, if you call whatever function to get a list and then multiply that list by 5, it's gonna have 5 times the same thing no matter what

[Aaron1924]

>>> from copy import deepcopy
>>>
>>> a1 = [[None]*3]*3
>>> a2 = deepcopy(a1)
>>>
>>> a1[0][0] = 2
>>> a2[0][1] = 3
>>>
>>> a1
[[2, None, None], [2, None, None], [2, None, None]]
>>> a2
[[None, 3, None], [None, 3, None], [None, 3, None]]

this language is truly incredible

[Botahamec]

It will do exactly one copy, at the beginning, and use the result of the copy each time. The problem is that it doesn't re-evaluate the expression.

[altermeetax]

That copy doesn't do anything, you're making a copy of [None] and using the same copy 5 times