join two list in a list oython code example

Example 1: join lists python

first_list = ["1", "2"]
second_list = ["3", "4"]

# Multiple ways to do this:
first_list += second_list
first_list = first_list + second_list
first_list.extend(second_list)

Example 2: merge lists in list python

import itertools
a = [['a','b'], ['c']]
print(list(itertools.chain.from_iterable(a)))