Flatten 2D list in Python

Question

I have a 2D list in python. How do I flatten the list?

Answer 1

Here's an example for you:

mat = [[10, 20, 30, 40], [50, 60, 70, 80], [90, 100, 110, 120]]
flatlist = []
for sublist in mat:
   for item in sublist:
      flatlist.append(item)
print (flatlist)

Suppose you have a 2D list called mat, all you've to do is, crawl through the list elements and flatten the list by appending the list items one after the other.