Question

I have a list M below which came from an external file (This is a large list in reality, len(M)>10000).

M=[(1, 100), (2, 200), (3, 300), (4, 400)]

However, I want to separate it into M1=[1,2,3,4] and M2=[100,200,300,400].
Here is how I do it at the moment,

M1 = [] 
M2 = [] 
for M1,M2 in M:
  M1.append(M1) 
  M2.append(M2)

I was wondering if there is a simpler and more efficient way to do it, a solution that uses built-in functions in Python.

Answer 1

Just do it:

M1, M2 = zip(*M)

M1 and M2 will be tuples. You can transform them into lists if you want:

M1, M2 = map(list, zip(*M))

or with a genexp:

M1, M2 = (list(i) for i in zip(*M))