How do I concatenate two lists in Python?

There are a few ways to concatenate lists in Python. Here are a few options:

1. Use the + operator:

Concatenating lists in Python using the + operator

list1 = [1, 2, 3]
list2 = [4, 5, 6]
list3 = list1 + list2

list3 will be equal to [1, 2, 3, 4, 5, 6].

2. Use the extend() method:

Concatenating lists in Python using the extend method

list1 = [1, 2, 3]
list2 = [4, 5, 6]
list1.extend(list2)

list1 will be equal to [1, 2, 3, 4, 5, 6].

3. Use the unpacking syntax:

Concatenating lists in Python using unpacking

list1 = [1, 2, 3]
list2 = [4, 5, 6]
list3 = [*list1, *list2]

list3 will be equal to [1, 2, 3, 4, 5, 6].

4. Use the itertools module:

Concatenating lists in Python using itertools module

import itertools
list1 = [1, 2, 3]
list2 = [4, 5, 6]
list3 = list(itertools.chain(list1, list2))

list3 will be equal to [1, 2, 3, 4, 5, 6]. Note that itertools.chain is ideal for concatenating multiple iterables. For a single iterable containing multiple iterables, itertools.chain.from_iterable() is more efficient.

Note that the + operator, unpacking, and itertools.chain all create a new list. If you want to modify the original list in place, use the extend() method or the += operator.