What does extend mean in python

When talking about extend, we have to mention append.

Look at the code first, and then explain the principle

Principle:

The two methods extend and append of Lists look like Similar, but actually completely different. extend accepts a parameter, which is always a list, and adds each element in this list to the original list.

Here there are 3 elements in the list ('a', 'b' and 'c'), and use another one with 3 elements ('d', 'e' and 'f') list is expanded so there are 6 elements in the new list.

Append, on the other hand, accepts a parameter, which can be of any data type, and is simply appended to the end of the list. Here the append method is called with a list parameter containing 3 elements.

The original list containing 3 elements now contains 4 elements. Why 4 elements? Because the last element just appended is itself a list. Lists can contain any type of data, including other lists. This may or may not be the result you want. If your intention is to extend, don't use append.

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