"""
Compare two version numbers version1 and version2.
If version1 > version2 return 1, if version1 < version2 return -1, otherwise return 0.

You may assume that the version strings are non-empty and contain only digits and the . character.
The . character does not represent a decimal point and is used to separate number sequences.
For instance, 2.5 is not "two and a half" or "half way to version three", it is the fifth second-level revision of the
second first-level revision.

Here is an example of version numbers ordering:

0.1 < 1.1 < 1.2 < 13.37
"""


def compare(version1, version2):
    subs1 = version1.split('.')
    subs2 = version2.split('.')

    i = 0
    n = max(len(subs1), len(subs2))
    while i < n:
        a = int(subs1[i]) if i < len(subs1) else 0
        b = int(subs2[i]) if i < len(subs2) else 0
        if a < b or a < b:
            return -1
        elif a > b or a > b:
            return 1

    return 0


if __name__ == '__main__':
    print compare('2.0', '1.9')
