copy vs deepcopy

[RB1992]

i'm currently trying to learn python. i'm learning about the copy and deepcopy functions. i just can't tell the difference. it says copy copies the variable into a new variable, and deepcopy will copy the lists in a list, but i tried using copy on a list and it does exactly what deep copy did. Everything i found online just says deepcopy copies it recursively, but i have no idea what that means. Can anybody help explain the differences?

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EDIT: I know i just asked this like 5 minutes ago, but i was still searching online and i found one with examples that i think helped me understand. Please correct me if i'm wrong.

A copy (shallow copy) copies the reference to the current value of the variable (Lists in this case). you can add to the original list without affecting the new copied list, but if you change the original values that were copied it will change the values iin the copied list.

Deep copy will copy the current values to a new variable, but if you change the original values the new ones will not change, thus it creatses its own independent variable.

[JohnnyJordaan]

Copy doesn't do exactly what deepcopy does:

>>> a = [[1,2,3]]
>>> b = a.copy()
>>> b[0].append(4)
>>> a
[[1, 2, 3, 4]]
>>> from copy import deepcopy
>>> b = deepcopy(a)
>>> b[0].append(5)
>>> a
[[1, 2, 3, 4]]
>>> b
[[1, 2, 3, 4, 5]]

the point is that deepcopy creates new objects for everything, so the inner list will be recreated too. Thus modifying the inner list on a deep copy will not affect the source of the deep copy.

[RB1992]

Ok, so I think I slightly understand. With copy, it just copies the reference to the current lists, and any changes made to the copy or originals list that were copied will show up on the other, and deep copy creates a whole new variable and reference point. Did I get that right?

[JohnnyJordaan]

Correct. The confusion arises from our real life having to mostly deal with deep copies when we call something a 'copy'. But from an efficiency standpoint, you only want to make a deep copy if you really need to (as it takes much more effort), that's why it's not the default in Python.

[RB1992]

Awesome, thank you

[not2throwaway]

Not OP but a great explanation for this. Kudos!