In [7]: def _while(x):
   ...:     n = 0
   ...:     while n < x:
   ...:         n += 1
   ...: 

In [8]: def _for(x):
   ...:     for i in xrange(x):
   ...:         pass
   ...: 

In [10]: %timeit _while(100)
100000 loops, best of 3: 20.3 µs per loop

In [11]: %timeit _for(100)
100000 loops, best of 3: 7.93 µs per loop