return list of list into list python code example

Example 1: python flat list from list of list

flat_list = [item for sublist in l for item in sublist]

#which is equivalent to this 
flat_list = []
for sublist in l:
    for item in sublist:
        flat_list.append(item)

Example 2: flatten a list of lists python

flattened = [val for sublist in list_of_lists for val in sublist]