quetion about "+=" and "runtime"

[gagaguy at gmail.com]

1.i have look " += " up,but i can't find it.is it ofthen used?
2.i saq a result like this in a web page:


$ time python permute2.py 56789 3
Got 120 items.
Maximum at 87596 ,product 84000

real    0m0.057s
user    0m0.050s
sys     0m0.000s

$ time python permute3.py 56789 3
Got 120 items.
Maximum at 87596 ,product 84000

real    0m0.040s
user    0m0.030s 
sys     0m0.010s 

i wanna know how to call out this