Question

simple Python question:

Example list: A = [1,2,3,4,5]

I need to generate another list B which is a shallow copy of list A such that B is a new list containing the same elements in the same order (so that I can substitute one of B’s elements w/o affecting A). How can I do this?

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clarification: I want to do something like

def some_func(A)
   B = {what do I do here to get a copy of A's elements?}
   B[0] = some_other_func(B[0])
   yet_another_func(B)

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based on all your answers + the Python docs, a better way to do what I want is the following:

def some_func(A)
   B = [some_other_func(A[0])] + A[1:]
   yet_another_func(B)

thanks for pointing me in the right direction!

Answer 1

Here are 3 ways to make a copy of list A:

Use slice notation:

copy_of_A = A[:]

Use the list constructor:

copy_of_A = list(A)

Use the copy module:

from copy import copy
copy_of_A = copy(A)

As you requested these copies are all shallow copies. To learn about the difference between shallow copy and deep copy read the documentation of the copy module.