copy a list in python

Question

Please what's the difference between this two codes in python:

white=[2,4,8,9]
black = white

and

white=[2,4,8,9]
black = white[:]

thank you so much.

Answer 1

The first copies a reference to the list white to the variable black

So any changes to black will also alter white and visa versa

Think of it as an alias or nickname for white

The second copies the contents of the list white to the variable black and is perhaps better written like this

black = list(white)

In this case there is no connection between the two variables black and white as it is the contents of white that are copied and not a reference to white itself.

Extra to take into account the relevant comment below (thanks Jon Clements): you can read more about deep copies vs shallow copies here Understanding dict.copy() - shallow or deep?