flatten list in python

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

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)

regular_list = [[1, 2, 3, 4], [5, 6, 7], [8, 9]]
flat_list = [item for sublist in regular_list for item in sublist]
print('Original list', regular_list)
print('Transformed list', flat_list)

regular_list = [[1, 2, 3, 4], [5, 6, 7], [8, 9]]
flat_list = [item for sublist in regular_list for item in sublist]
print('Original list', regular_list)
print('Transformed list', flat_list)

regular_list = [[1, 2, 3, 4], [5, 6, 7], [8, 9]]
flat_list = [item for sublist in regular_list for item in sublist]
print('Original list', regular_list)
print('Transformed list', flat_list)