Python lists

Question

I’m just a beginner so this is probably really basic, but why does this

a = [1, 2, 3, 4]
b= a
b = b.remove(4)
print(a)

Output [1, 2, 3]

Shouldn’t a and b be independent from each other?

Answer 1

It is because 'b' is not a copy of 'a'.
Reference of 'a' is assigned to 'b'.
It means both the variables are pointing to the same list in the memory. You can use either one of them to make any changes to the list and it will be reflected in both.

Answer 2

Hi, ES135!
You can look at this one:

https://code.sololearn.com/c6HP42TW4Q5O/?ref=app

If you don’t want a and b to be referenced to the same object, you can do a (shallow) copy of the list: b = a[:] or b = a.copy().

Answer 3

Thank you for all the answers :)

Answer 4

The answer is in this topic:

https://stackoverflow.com/questions/19951816/JUMP_LINK__&&__python__&&__JUMP_LINK-changes-to-my-copy-variable-affect-the-original-variable

Answer 5

a is assigned to b. So when you print 'b' it should output 1, 2, 3, 4. So when you remove 4 from b you are removing 4 from the list. Therefore it outputs 1, 2, 3