Line-by-line code profiling in Python

Oct 1st, 2015 in Python by Michael Cho

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How to find slow sections in your Python code.

An easy way to find the slow sections of your python code.

Add the profiler library


pip install line_profiler

Add @profile decorator

Above the function to profile, e.g.:


@profile
def parse_teams_cache(teams, include_search=False, user=None):
    team_items = []
    .... etc ...

Enable the function / file to be called from the command line

By adding something like the following to the bottom of the file:


if __name__ == "__main__":
    teams = Group.leaders()
    user = User.query.get(5347)
    parse_teams_cache(teams, include_search=False, user=user)

Run the profiler


kernprof -l -v pages/helpers/team_helper.py

Results

Results show the slowest code is in loading the cache, ie:


Line #      Hits         Time  Per Hit   % Time  Line Contents
==============================================================
   143                                           @profile
   144                                           def parse_teams_cache(teams):
   145         1            2      2.0      0.0      team_items = []
   146        27           27      1.0      0.0      for team in teams:
   147        26          185      7.1      0.2          team_cache_key = ...
   148        26        99097   3811.4     98.5          team_cache = ...
   149        26           47      1.8      0.0          if team_cache:
   150        26         1154     44.4      1.1              team_item = ...