How to use timeit module

If you want to use timeit in an interactive Python session, there are two convenient options:

1. Use the IPython shell. It features the convenient %timeit special function:

   In [1]: def f(x):
      ...:     return x*x
      ...: 
   
   In [2]: %timeit for x in range(100): f(x)
   100000 loops, best of 3: 20.3 us per loop
   

2. In a standard Python interpreter, you can access functions and other names you defined earlier during the interactive session by importing them from __main__ in the setup statement:

   >>> def f(x):
   ...     return x * x 
   ... 
   >>> import timeit
   >>> timeit.repeat("for x in range(100): f(x)", "from __main__ import f",
                     number=100000)
   [2.0640320777893066, 2.0876040458679199, 2.0520210266113281]