Python 2.7.10:

String of len: 1 took:     0.4830     0.2990 seconds
String of len: 4 took:     0.7270     0.4400 seconds
String of len: 6 took:     0.9650     0.5440 seconds
String of len: 12 took:     1.5160     0.8450 seconds
String of len: 80 took:     6.8230     3.8810 seconds
String of len: 222 took:    17.1750    10.7700 seconds
String of len: 443 took:    33.0310    21.9950 seconds

Python 3.5.2:

String of len: 1 took:     0.3653     0.1944 seconds
String of len: 4 took:     0.6361     0.3704 seconds
String of len: 6 took:     0.8627     0.4727 seconds
String of len: 12 took:     1.3805     0.7927 seconds
String of len: 80 took:     6.8161     4.6341 seconds
String of len: 222 took:    16.8068    12.5249 seconds
String of len: 443 took:    32.2237    24.9165 seconds