[Python-Dev] Python startup time (original) (raw)
Victor Stinner victor.stinner at gmail.com
Wed Jul 19 10:26:56 EDT 2017
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2017-07-19 15:22 GMT+02:00 Oleg Broytman <phd at phdru.name>:
On Wed, Jul 19, 2017 at 02:59:52PM +0200, Victor Stinner <victor.stinner at gmail.com> wrote:
"Python is very slow to start on Windows 7" https://stackoverflow.com/questions/29997274/python-is-very-slow-to-start-on-windows-7 However hard you are going to optimize Python you cannot fix those "defenders", "guards" and "protectors". :-) This particular link can be excluded from consideration.
Sorry, I didn't read carefully each link I posted. Even for me knowing what Python does at startup, it's hard to explain why 3 people have different timing: 15 ms, 75 ms and 300 ms for example. In my experience, the following things impact Python startup:
- -S option: loading or not the site module
- Paths in sys.path: PYTHONPATH environment variable for example
- .pth files files in sys.path
- Python running in a virtual environment or not
- Operating system: Python loads different modules at startup depending on the OS. Naoki INADA just removed _osx_support from being imported in the site module on macOS for example.
My list is likely incomplete.
In the performance benchmark suite, a controlled virtual environment is created to have a known set of modules. FYI running Python is a virtual environment is slower than "system" python which runs outside a virtual environment...
Victor
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