On the documentation page "The Python Profilers" https://docs.python.org/3.4/library/profile.html#instant-user-s-manual the following example is given:

p.sort_stats('time', 'cum').print_stats(.5, 'init')

This raises a KeyError, because 'cum' is not available as a sort key to pstats.Stats.sort_stats. As per the documentation of this method (https://docs.python.org/3.4/library/profile.html#the-stats-class) you can either use 'cumulative' or 'cumtime', which both work as expected.

Since 'cumulative' is used a few examples earlier I suggest to use that for consistency.

Tested with the following Python version:

Python 3.4.3 on Ubuntu 15.04