Python/Harmattan/Performance Considerations for Python Apps
Based on Python faster (for fmms initially) and Qt startup time tips
Contents |
Profiling
Do not worry about performance unless you notice a problem. Then only optimize what you can justify with profiling.
To profile Python code, run it with
$ python -m cProfile -o .profile TOPLEVEL_SCRIPT.py
To then analyze the results
$ python -m pstats .profile > sort cumulative > stats 40
That sorted the results by the time it took for a function and all the functions it called. It then displays the top 40 results.
Improving Performance
Interpreter Choice
Unladen Swallow
PEP 3146 - Merging of Unladen Swallow
Currently Unladen Swallow has not seen too much performance benefit but has a longer start up time and takes more memory
Psyco / Cython
Do these work with Arm?
Shedskin
C with CTypes
Startup
/usr/bin/python Startup
Preloaders exists like PyLauncher that keep a python process around with heavy weight imports like gtk already imported. On application launch it forks the preloader process.
Preloaders were favored back in the Maemo 4.1 days but has fallen out of favor lately. Concerns center around always keeping an unused python process with heavy pieces of code imported always around [1].
Parsing .py files
Perceived Startup Performance
hildon_gtk_window_take_screenshot takes advantage of user perception to make the user think the app is launched faster.
Responsiveness
Memory Usage
FAQ
Is Python slow?
The standard response of "it depends". For a graphical application not doing too much processing a user will probably not notice it is written in Python. Compare that to an experiment by epage in writing a GST video filter in python that at best ran at 2 seconds per frame.