Python/initconfig.c

Source:

cpython 3.14 @ ab2d84fe1023/Python/initconfig.c ↗

Python/initconfig.c implements the configuration pipeline that translates command-line arguments and environment variables into the PyConfig struct that controls interpreter initialization. It is the implementation of PEP 587 (PyConfig) and PEP 578 (audit hooks).

Map

Lines	Symbol	Role
1-300	PyPreConfig	Pre-init configuration: allocator, locale, UTF-8 mode
301-700	PyConfig fields and defaults	All 70+ config fields with their defaults
701-1200	_PyConfig_Read	Read config from argv, env vars, PyConfig fields
1201-1600	config_init_argv, config_init_env	Argv and environment parsing
1601-2000	config_init_sys_path_config	sys.path construction
2001-2800	PyConfig_InitPythonConfig, PyConfig_InitIsolatedConfig, PyConfig_SetArgv	Public API

Reading

PyConfig key fields

// CPython: Include/cpython/initconfig.h PyConfig (excerpt)
struct PyConfig {
    int  isolated;          // -I flag
    int  use_environment;   // read env vars
    int  dev_mode;          // -X dev
    int  install_signal_handlers;
    int  use_hash_randomization;
    int  faulthandler;
    int  tracemalloc;
    int  int_max_str_digits; // -X int_max_str_digits
    int  optimization_level; // -O
    int  parser_debug;       // -d
    int  verbose;            // -v
    int  quiet;              // -q
    wchar_t *program_name;
    PyWideStringList argv;
    PyWideStringList xoptions;  // -X options
    PyWideStringList warnoptions;
    wchar_t *pythonpath_env;   // PYTHONPATH
    PyWideStringList module_search_paths;
    ...
};

_PyConfig_Read

Reads configuration sources in priority order:

1. Programmatically set fields in PyConfig
2. Command-line arguments (argv)
3. Environment variables (PYTHONPATH, PYTHONUTF8, etc.)
4. Python path configuration file (._pth files)
5. Compiled-in defaults

// CPython: Python/initconfig.c:3280 _PyConfig_Read
PyStatus
_PyConfig_Read(PyConfig *config, int compute_path_config)
{
    status = config_read_env_vars(config);
    ...
    status = config_read_cmdline(config);
    ...
    if (compute_path_config)
        status = config_init_path_config(config, 0);
    ...
}

PyConfig_InitIsolatedConfig

Initializes a config with all environment-reading and site-package loading disabled, suitable for embedding Python in an application that manages its own environment.

// CPython: Python/initconfig.c:1035 PyConfig_InitIsolatedConfig
void
PyConfig_InitIsolatedConfig(PyConfig *config)
{
    config->isolated = 1;
    config->use_environment = 0;
    config->user_site_directory = 0;
    config->site_import = 0;
    ...
}

gopy notes

Status: not yet ported as a full PyConfig. gopy's startup configuration is currently hardcoded. A future PyConfig port would allow embedding applications to control gopy the same way CPython embedding works. The key fields needed immediately are argv, pythonpath_env, optimization_level, and verbose.