THIS Feature Made Me Cry In Python #code #python #programming

This feature made me cry in Python #code #python #programming

[BenoitCOMPERE]

It's not only Python, all languages have this distinction between a shallow copy and a deep copy

[vorpal]

At my last job, we had a huge data model represented as a tree where most of the nodes were immutable but some were mutable and we wanted the immutable ones to be not copied at all (just return the reference) and the others to be recursively copied, so I made an @immutable decorator that could be used to abort copying / deep copying, and it worked very well and drastically reduced memory use and increased performance.

[danutmh]

you would think that copy should be making a deepcopy and shallowcopy be a separate function, not the other way around

[ElementEvilTeam]

I just tested it. [:] creates a shallow copy.
>>> a = [0, ['a', 'b'], 2]
>>> b = a[:]
>>> b[1][0] = 'Bob'
>>> print(a)
[0, ['Bob', 'b'], 2]
>>> print(b)
[0, ['Bob', 'b'], 2]

[olivierDurand-zhvu]

I use both C++ and python, and if you do a vector of variant in C++, copy works. Copy in C++ is deep copy else we talk of reference.

[fredtrunce]

I had this exact problem with a game that I made and it took me forever to figure out why it was doing this

[rawesomeness_]

down side of not being able to use pointers

[firebolt]

yuss, i used this method to create child nodes for my minimax algorithm

[classmanOfficial]

This happens for lists inside dictionaries too!!!, how am I just learning this 0-0

[emre_ez]

when i first started coding i used to just use a for loop to copy them so this wouldnt happen

[leokillerable]

So then what is the point of having a copy method on list if b = a.copy() is equivalent to just b = a ?

[raiyaanshaikh]

Array names are essentially pointers! It's an interesting (often annoying) feature, but I can see why one would use it.

[xsamueljr]

Would `list.copy()` be enough if there are no nested lists inside?

[luluw]

Its because .copy() points to memory location.

[dragweb]

i feel like doing b = a[:] could work too, but maybe i'm wrong i didn't test it with a nested container

[robinpipslayertekprofitsfa]

Wait....that's a Python built-in?! 🤯🤯🤯🤯

[javiarfasyah]

I think you'll need recursive copy

[tomasslavik]

You can design your own recursive deepcopy function.

[midlander]

Given Python's behavior shown in the video, I thought "b=a.copy()" would just make b a pointer to the "a" memory chunk, but the behavior shown in the video refers to a nested list. If a=[1, 2, 3] and b=a.copy(), then b[1]=5, say, makes b=[1, 5, 3], but still a=[1, 2, 3] (use appropriate "print" statements), so "b" is not just a pointer to variable "a" under b=a.copy(). I honestly don't know what's going on.

[staywithmeforever]

I don't even use copy or deep copy
B=list(a)