regular expression: may or may not contain a string

I want to match a floating number that might be in the form of 0.1234567 or 1.23e-5 Here is my python code:

import re
def main():
    m2 = re.findall(r'\d{1,4}:[-+]?\d+\.\d+(e-\d+)?', '1:0.00003 3:0.123456 8:-0.12345')
    for svs_elem in m2:
         print svs_elem

main()

It prints blank... Based on my test, the problem was in (e-\d+)? part. Thank you!