How to convert an H:MM:SS time string to seconds in Python?

def get_sec(time_str):
    """Get seconds from time."""
    h, m, s = time_str.split(':')
    return int(h) * 3600 + int(m) * 60 + int(s)


print(get_sec('1:23:45'))
print(get_sec('0:04:15'))
print(get_sec('0:00:25'))