ipython - What is %timeit in python?

Question

I always read the code to calculate the time like this way:

%timeit function()

Can you explain what means "%" here?

I think, the "%" is always used to replace something in a string, like %s means replace a string, %d replace a data, but I have no idea about this case.

Answer 1

%timeit is an ipython magic function, which can be used to time a particular piece of code (A single execution statement, or a single method).

From the docs:

%timeit

Time execution of a Python statement or expression

Usage, in line mode:
    %timeit [-n<N> -r<R> [-t|-c] -q -p<P> -o] statement

To use it, for example if we want to find out whether using xrange is any faster than using range, you can simply do:

In [1]: %timeit for _ in range(1000): True
10000 loops, best of 3: 37.8 μs per loop

In [2]: %timeit for _ in xrange(1000): True
10000 loops, best of 3: 29.6 μs per loop

And you will get the timings for them.

The major advantage of %timeit are:

• that you don't have to import timeit.timeit from the standard library, and run the code multiple times to figure out which is the better approach.

• %timeit will automatically calculate number of runs required for your code based on a total of 2 seconds execution window.

• You can also make use of current console variables without passing the whole code snippet as in case of timeit.timeit to built the variable that is built in an another environment that timeit works.