Function BPY_python_start

source/blender/python/intern/bpy_interface.cc:351–634

#endif

void BPY_python_start(bContext *C, int argc, const char **argv)
{
#ifndef WITH_PYTHON_MODULE
  BLI_assert_msg(Py_IsInitialized() == 0, "Python has already been initialized");

  /* It's necessary to disable isolation so `user-site-packages` can be used.
   * Leave everything else disabled (mainly environment variables). */
  const std::optional<bool> isolated_override = ((py_use_system_env == false) &&
                                                 (py_use_user_env == true)) ?
                                                    std::optional(false) :
                                                    std::nullopt;

  /* #PyPreConfig (early-configuration). */
  {
    PyPreConfig preconfig;
    PyStatus status;

    /* To narrow down reports where the systems Python is inexplicably used, see: #98131. */
    CLOG_DEBUG(BPY_LOG_INTERFACE,
               "Initializing %s support for the systems Python environment such as 'PYTHONPATH', "
               "%s support for the user-site directory.",
               py_use_system_env ? "*with*" : "*without*",
               py_use_user_env ? "*with*" : "*without*");

    if (py_use_system_env) {
      PyPreConfig_InitPythonConfig(&preconfig);
    }
    else {
      /* Only use the systems environment variables and site when explicitly requested.
       * Since an incorrect 'PYTHONPATH' causes difficult to debug errors, see: #72807.
       * An alternative to setting `preconfig.use_environment = 0` */
      PyPreConfig_InitIsolatedConfig(&preconfig);
    }

    if (isolated_override) {
      preconfig.isolated = isolated_override.value();
    }

    /* Force UTF8 on all platforms, since this is what's used for Blender's internal strings,
     * providing consistent encoding behavior across all Blender installations.
     *
     * This also uses the `surrogateescape` error handler ensures any unexpected bytes are escaped
     * instead of raising an error.
     *
     * Without this `sys.getfilesystemencoding()` and `sys.stdout` for example may be set to ASCII
     * or some other encoding - where printing some UTF8 values will raise an error.
     *
     * This can cause scripts to fail entirely on some systems.
     *
     * This assignment is the equivalent of enabling the `PYTHONUTF8` environment variable.
     * See `PEP-540` for details on exactly what this changes. */
    preconfig.utf8_mode = true;

    /* Note that there is no reason to call #Py_PreInitializeFromBytesArgs here
     * as this is only used so that command line arguments can be handled by Python itself,
     * not for setting `sys.argv` (handled below). */
    status = Py_PreInitialize(&preconfig);
    pystatus_exit_on_error(status);