Bug report

3.11.0b1 appears to have a regression in the behavior of Py_InitializeFromConfig() in the way that sys.path is computed.

Reproduction case 1:

This code attempts to set the path through the config.pythonpath_env variable.

int main(int argc, char *argv[]) { PyConfig config; PyConfig_InitIsolatedConfig(&config); PyConfig_SetString(&config, &config.pythonpath_env, L"/path/to/app:/other/path"); Py_InitializeFromConfig(&config); PyRun_SimpleString("import sys; print(f'{sys.path=}')"); return 0 } 

In Python 3.8.13, 3.9.12 and 3.10.4, this code shows 6 items when sys.path is printed:

• /path/to/app
• /other/path
• /path/to/Python/lib/python3X.zip
• /path/to/Python/lib/python3.X
• /path/to/Python/lib/python3.X/lib-dynload
• /path/to/Python/lib/python3.X/site-packages

In Python 3.11.0b1, the first two items are not present.

Reproduction case 2:

This example is a closer match to the "more complete example" in the docs; it reads a full configuration, then appending the extra search paths.

int main(int argc, char *argv[]) { PyConfig config; PyConfig_InitIsolatedConfig(&config); PyConfig_Read(&config); PyWideStringList_Append(&config.module_search_paths, L"/path/to/app"); PyWideStringList_Append(&config.module_search_paths, L"/other/path"); Py_InitializeFromConfig(&config); PyRun_SimpleString("import sys; print(f'{sys.path=}')"); return 0 } 

Again, in Python 3.8.13, 3.9.12 and 3.10.4, this code shows 6 items when sys.path is printed (although the order is different):

• /path/to/Python/lib/python3X.zip
• /path/to/Python/lib/python3.X
• /path/to/Python/lib/python3.X/lib-dynload
• /path/to/app
• /other/path
• /path/to/Python/lib/python3.X/site-packages

In Python 3.11.0b1, this raises an error, dumping the path configuration with _Py_DumpPathConfig(). This appears to be because it's modifying the path enough to make the encodings module unimportable.

If the 2 path appends are omitted (but the PyConfig_Read() call is retained), it runs, and outputs sys.path - but with the 2 custom module search paths missing.

Analysis

As best as I can make out, the regression was introduced by 99fcf15 (cc @zooba) as part of a refactor of getpath().

Your environment

Observed in Python 3.11.0b1 on macOS 12.3.1 on M1 hardware; however, I don't think there's anything Mac specific about it.

FWIW, I discovered this while porting the support library used by Briefcase to publish macOS and iOS apps.