Tips to avoid for loops
PythonSpeed/PerformanceTips - Python Wiki
Use More Iterators
python - Using numpy arrays to avoid for loops - combinatorics - Stack Overflow
Pythonで多重forループを避ける簡単な手法 - Qiita
multiprocessing - what is the neat way to divide huge nested loops to 8(or more) processes using Python? - Stack Overflow