how to unlist a list in python

# Basic syntax:
unnested_list = list(chain(*nested_list))
# Where chain comes from the itertools package and is useful for 
#	unnesting any iterables

# Example usage:
from itertools import chain
nested_list = [[1,2], [3,4]]
my_unnested_list = list(chain(*nested_list))
print(my_unnested_list)
--> [1, 2, 3, 4]

Here is what the above code is Doing:
1. Importing the chain function from the itertools package
2. Creating a nested list
3. Creating a variable that stores the result of the chain function
4. Printing the result