The %timeit magic command is often helpful, yet a bit limited when you need detailed information about what takes most of the execution time in your code. This magic command is meant for benchmarking (comparing the execution times of different versions of a function) rather than profiling (getting a detailed report of the execution time, function by function).
Python includes a profiler named cProfile that breaks down the execution time into the contributions of all called functions. IPython provides convenient ways to leverage this tool in an interactive session.
IPython offers the %prun line magic and the %%prun cell magic to easily profile one or multiple lines of code. The %run magic command also accepts a -p flag to run a Python script under the control of the profiler. These commands accept a lot of options, and you may want to take a look at their documentation with %prun? and %run?.