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Python Python Basics (2015) Python Data Types Splitting and Joining

Ivica Dimitrijev
Ivica Dimitrijev
1,466 Points
Posted by Ivica Dimitrijev
Ivica Dimitrijev
1,466 Points

List problem: var_one and var_two

If I write: var_one = ["a", "b", "c"] var_two = var_one print(var_two)

I get: ['a', 'b', 'c']

But if I write: var_one = ["a", "b", "c"] var_two = var_one.extend(["d", "e"]) I get empty list or None

Why is that?

I'm sure it was mentioned in the videos but can't find it.

2 Answers

Stuart Wright
Stuart Wright
41,118 Points
Stuart Wright
Stuart Wright
41,118 Points

The extend() method alters a list in place, and returns None. So if you say:

var_two = var_one.extend(["d", "e"])

var_one will now have the new elements appended to it (check it out in the console), but var_two will be equal to None, since that is what extend() returns.

An alternative syntax if you want to assign to a new variable rather than change in place would be simply:

var_two = var_one + ["d", "e"]