What's the equivalent for while (cin >> var) in python?

There's no direct equivalent in Python. But you can simulate it with two nested loops:

for line in sys.stdin:
    for var in line.split():

If you need something other than a string you'll need to convert it in a separate step:

        var = int(var)

This could be helpfull.

import sys

for line in sys.stdin:
    #Do stuff