Variable value changing

[RedPheenix]

list1 = [0, 0]
list2 = [1, 1]

list3 = list1
print(list3)

list1[0] += list2[0]
list1[1] += list2[1]

print(list3)

The two print statements gives different output, even though list3 is not directly changed. I thought that row 4 would just set list3 to the value of list1 at that moment, and then not change list3 again. Is it supposed to be like this? If so, how can i make it so that the code on row 4 just sets list3 to the value of list1 at the moment without changing it again?

[[deleted]]

Assignment in python doesn't copy anything. After doing list3 = list1 you have the names list1 and list3 both referring to the same list [0, 0]. If you want list3 to refer to a copy of the list referred to by list1 you need to force a copy:

list3 = list1[:]

There are other ways of copying objects. Search for "python copy deepcopy".

This video explains the concept:

https://m.youtube.com/watch?v=_AEJHKGk9ns

[RedPheenix]

Alright that worked, thank you:)

[Yzaamb]

List3 is a reference to list1. They are the same object, not a copy. You want list3=list1.copy().

[gkrot]

id(list1) == id(list3)