Python初始化配置

3.8 新版功能.

Python can be initialized with Py_InitializeFromConfig() and the PyConfig structure. It can be preinitialized with Py_PreInitialize() and the PyPreConfig structure.

There are two kinds of configuration:

  • The Python Configuration can be used to build a customized Python which behaves as the regular Python. For example, environments variables and command line arguments are used to configure Python.

  • The Isolated Configuration can be used to embed Python into an application. It isolates Python from the system. For example, environments variables are ignored, the LC_CTYPE locale is left unchanged and no signal handler is registred.

The Py_RunMain() function can be used to write a customized Python program.

See also Initialization, Finalization, and Threads.

参见

PEP 587 “Python 初始化配置”.

示例

Example of customized Python always running in isolated mode:

  1. int main(int argc, char **argv)
  2. {
  3.     PyStatus status;
  5.     PyConfig config;
  6.     PyConfig_InitPythonConfig(&config);
  7.     config.isolated = 1;
  9.     /* Decode command line arguments.
  10.        Implicitly preinitialize Python (in isolated mode). */
  11.     status = PyConfig_SetBytesArgv(&config, argc, argv);
  12.     if (PyStatus_Exception(status)) {
  13.         goto exception;
  14.     }
  16.     status = Py_InitializeFromConfig(&config);
  17.     if (PyStatus_Exception(status)) {
  18.         goto exception;
  19.     }
  20.     PyConfig_Clear(&config);
  22.     return Py_RunMain();
  24. exception:
  25.     PyConfig_Clear(&config);
  26.     if (PyStatus_IsExit(status)) {
  27.         return status.exitcode;
  28.     }
  29.     /* Display the error message and exit the process with
  30.        non-zero exit code */
  31.     Py_ExitStatusException(status);
  32. }

PyWideStringList

type PyWideStringList

List of wchar_t* strings.

If length is non-zero, items must be non-NULL and all strings must be non-NULL.

方法

  • PyStatus PyWideStringList_Append(PyWideStringList list, const* wchar_t item*)

    Append item to list.

    Python must be preinitialized to call this function.

  • PyStatus PyWideStringList_Insert(PyWideStringList list, Py_ssize_t index, const* wchar_t item*)

    Insert item into list at index.

    If index is greater than or equal to list length, append item to list.

    index must be greater than or equal to 0.

    Python must be preinitialized to call this function.

Structure fields:

  • Py_ssize_t length

    List 长度。

  • wchar_t **items

    列表项目。

PyStatus

type PyStatus

Structure to store an initialization function status: success, error or exit.

For an error, it can store the C function name which created the error.

Structure fields:

  • int exitcode

    Exit code. Argument passed to exit().

  • const char *err_msg

    错误信息

  • const char *func

    Name of the function which created an error, can be NULL.

Functions to create a status:

  • PyStatus PyStatus_Ok(void)

    完成。

  • PyStatus PyStatus_Error(const char *err_msg)

    Initialization error with a message.

    err_msg must not be NULL.

  • PyStatus PyStatus_NoMemory(void)

    Memory allocation failure (out of memory).

  • PyStatus PyStatus_Exit(int exitcode)

    以指定的退出代码退出 Python。

Functions to handle a status:

  • int PyStatus_Exception(PyStatus status)

    Is the status an error or an exit? If true, the exception must be handled; by calling Py_ExitStatusException() for example.

  • int PyStatus_IsError(PyStatus status)

    结果错误吗？

  • int PyStatus_IsExit(PyStatus status)

    结果是否退出？

  • void Py_ExitStatusException(PyStatus status)

    Call exit(exitcode) if status is an exit. Print the error message and exit with a non-zero exit code if status is an error. Must only be called if PyStatus_Exception(status) is non-zero.

注解

Internally, Python uses macros which set PyStatus.func, whereas functions to create a status set func to NULL.

示例:

  1. PyStatus alloc(void **ptr, size_t size)
  2. {
  3.     *ptr = PyMem_RawMalloc(size);
  4.     if (*ptr == NULL) {
  5.         return PyStatus_NoMemory();
  6.     }
  7.     return PyStatus_Ok();
  8. }
  10. int main(int argc, char **argv)
  11. {
  12.     void *ptr;
  13.     PyStatus status = alloc(&ptr, 16);
  14.     if (PyStatus_Exception(status)) {
  15.         Py_ExitStatusException(status);
  16.     }
  17.     PyMem_Free(ptr);
  18.     return 0;
  19. }

PyPreConfig

type PyPreConfig

Structure used to preinitialize Python.

Function to initialize a preconfiguration:

Structure fields:

Preinitialize Python with PyPreConfig

The preinitialization of Python:

The current preconfiguration (PyPreConfig type) is stored in _PyRuntime.preconfig.

Functions to preinitialize Python:

PyStatus Py_PreInitialize(const PyPreConfig *preconfig)

Preinitialize Python from preconfig preconfiguration.

preconfig must not be NULL.

PyStatus Py_PreInitializeFromBytesArgs(const PyPreConfig preconfig, int argc*, char const **argv)

Preinitialize Python from preconfig preconfiguration.

Parse argv command line arguments (bytes strings) if parse_argv of preconfig is non-zero.

preconfig must not be NULL.

PyStatus Py_PreInitializeFromArgs(const PyPreConfig preconfig, int argc*, wchar_t const **argv)

Preinitialize Python from preconfig preconfiguration.

Parse argv command line arguments (wide strings) if parse_argv of preconfig is non-zero.

preconfig must not be NULL.

The caller is responsible to handle exceptions (error or exit) using PyStatus_Exception() and Py_ExitStatusException().

For Python Configuration (PyPreConfig_InitPythonConfig()), if Python is initialized with command line arguments, the command line arguments must also be passed to preinitialize Python, since they have an effect on the pre-configuration like encodings. For example, the -X utf8 command line option enables the Python UTF-8 Mode.

PyMem_SetAllocator() can be called after Py_PreInitialize() and before Py_InitializeFromConfig() to install a custom memory allocator. It can be called before Py_PreInitialize() if PyPreConfig.allocator is set to PYMEM_ALLOCATOR_NOT_SET.

Python memory allocation functions like PyMem_RawMalloc() must not be used before the Python preinitialization, whereas calling directly malloc() and free() is always safe. Py_DecodeLocale() must not be called before the Python preinitialization.

Example using the preinitialization to enable the Python UTF-8 Mode:

  1. PyStatus status;
  2. PyPreConfig preconfig;
  3. PyPreConfig_InitPythonConfig(&preconfig);
  5. preconfig.utf8_mode = 1;
  7. status = Py_PreInitialize(&preconfig);
  8. if (PyStatus_Exception(status)) {
  9.     Py_ExitStatusException(status);
  10. }
  12. /* at this point, Python speaks UTF-8 */
  14. Py_Initialize();
  15. /* ... use Python API here ... */
  16. Py_Finalize();

PyConfig

type PyConfig

Structure containing most parameters to configure Python.

When done, the PyConfig_Clear() function must be used to release the configuration memory.

Structure methods:

Most PyConfig methods preinitialize Python if needed. In that case, the Python preinitialization configuration (PyPreConfig) in based on the PyConfig. If configuration fields which are in common with PyPreConfig are tuned, they must be set before calling a PyConfig method:

Moreover, if PyConfig_SetArgv() or PyConfig_SetBytesArgv() is used, this method must be called before other methods, since the preinitialization configuration depends on command line arguments (if parse_argv is non-zero).

The caller of these methods is responsible to handle exceptions (error or exit) using PyStatus_Exception() and Py_ExitStatusException().

Structure fields:

  • PyWideStringList argv

    Command line arguments: sys.argv.

    Set parse_argv to 1 to parse argv the same way the regular Python parses Python command line arguments and then to strip Python arguments from argv.

    If argv is empty, an empty string is added to ensure that sys.argv always exists and is never empty.

    Default: NULL.

    See also the orig_argv member.

  • wchar_t *base_exec_prefix

    sys.base_exec_prefix.

    Default: NULL.

    Part of the Python Path Configuration output.

  • wchar_t *base_executable

    Python base executable: sys._base_executable.

    Set by the __PYVENV_LAUNCHER__ environment variable.

    Set from PyConfig.executable if NULL.

    Default: NULL.

    Part of the Python Path Configuration output.

  • wchar_t *base_prefix

    sys.base_prefix.

    Default: NULL.

    Part of the Python Path Configuration output.

  • int buffered_stdio

    If equals to 0 and configure_c_stdio is non-zero, disable buffering on the C streams stdout and stderr.

    Set to 0 by the -u command line option and the PYTHONUNBUFFERED environment variable.

    stdin is always opened in buffered mode.

    Default: 1.

  • int bytes_warning

    If equals to 1, issue a warning when comparing bytes or bytearray with str, or comparing bytes with int.

    If equal or greater to 2, raise a BytesWarning exception in these cases.

    Incremented by the -b command line option.

    Default: 0.

  • int warn_default_encoding

    If non-zero, emit a EncodingWarning warning when io.TextIOWrapper uses its default encoding. See 选择性的 EncodingWarning for details.

    Default: 0.

    3.10 新版功能.

  • wchar_t *check_hash_pycs_mode

    Control the validation behavior of hash-based .pyc files: value of the --check-hash-based-pycs command line option.

    Valid values:

    • L"always": Hash the source file for invalidation regardless of value of the ‘check_source’ flag.

    • L"never": Assume that hash-based pycs always are valid.

    • L"default": The ‘check_source’ flag in hash-based pycs determines invalidation.

    Default: L"default".

    See also PEP 552 “Deterministic pycs”.

  • int configure_c_stdio

    If non-zero, configure C standard streams:

    • On Windows, set the binary mode (O_BINARY) on stdin, stdout and stderr.

    • If buffered_stdio equals zero, disable buffering of stdin, stdout and stderr streams.

    • If interactive is non-zero, enable stream buffering on stdin and stdout (only stdout on Windows).

    Default: 1 in Python config, 0 in isolated config.

  • int dev_mode

    If non-zero, enable the Python Development Mode.

    Default: -1 in Python mode, 0 in isolated mode.

  • int dump_refs

    Dump Python refererences?

    If non-zero, dump all objects which are still alive at exit.

    Set to 1 by the PYTHONDUMPREFS environment variable.

    Need a special build of Python with the Py_TRACE_REFS macro defined: see the configure --with-trace-refs option.

    Default: 0.

  • wchar_t *exec_prefix

    The site-specific directory prefix where the platform-dependent Python files are installed: sys.exec_prefix.

    Default: NULL.

    Part of the Python Path Configuration output.

  • wchar_t *executable

    The absolute path of the executable binary for the Python interpreter: sys.executable.

    Default: NULL.

    Part of the Python Path Configuration output.

  • int faulthandler

    Enable faulthandler?

    If non-zero, call faulthandler.enable() at startup.

    Set to 1 by -X faulthandler and the PYTHONFAULTHANDLER environment variable.

    Default: -1 in Python mode, 0 in isolated mode.

  • wchar_t *filesystem_encoding

    Filesystem encoding: sys.getfilesystemencoding().

    On macOS, Android and VxWorks: use "utf-8" by default.

    On Windows: use "utf-8" by default, or "mbcs" if legacy_windows_fs_encoding of PyPreConfig is non-zero.

    Default encoding on other platforms:

    • "utf-8" if PyPreConfig.utf8_mode is non-zero.

    • "ascii" if Python detects that nl_langinfo(CODESET) announces the ASCII encoding (or Roman8 encoding on HP-UX), whereas the mbstowcs() function decodes from a different encoding (usually Latin1).

    • "utf-8" if nl_langinfo(CODESET) returns an empty string.

    • Otherwise, use the locale encoding: nl_langinfo(CODESET) result.

    At Python statup, the encoding name is normalized to the Python codec name. For example, "ANSI_X3.4-1968" is replaced with "ascii".

    See also the filesystem_errors member.

  • wchar_t *filesystem_errors

    Filesystem error handler: sys.getfilesystemencodeerrors().

    On Windows: use "surrogatepass" by default, or "replace" if legacy_windows_fs_encoding of PyPreConfig is non-zero.

    On other platforms: use "surrogateescape" by default.

    Supported error handlers:

    • "strict"

    • "surrogateescape"

    • "surrogatepass" (only supported with the UTF-8 encoding)

    See also the filesystem_encoding member.

  • unsigned long hash_seed

  • int use_hash_seed

    Randomized hash function seed.

    If use_hash_seed is zero, a seed is chosen randomly at Python startup, and hash_seed is ignored.

    Set by the PYTHONHASHSEED environment variable.

    Default use_hash_seed value: -1 in Python mode, 0 in isolated mode.

  • wchar_t *home

    Python home directory.

    If Py_SetPythonHome() has been called, use its argument if it is not NULL.

    Set by the PYTHONHOME environment variable.

    Default: NULL.

    Part of the Python Path Configuration input.

  • int import_time

    If non-zero, profile import time.

    Set the 1 by the -X importtime option and the PYTHONPROFILEIMPORTTIME environment variable.

    Default: 0.

  • int inspect

    Enter interactive mode after executing a script or a command.

    If greater than 0, enable inspect: when a script is passed as first argument or the -c option is used, enter interactive mode after executing the script or the command, even when sys.stdin does not appear to be a terminal.

    Incremented by the -i command line option. Set to 1 if the PYTHONINSPECT environment variable is non-empty.

    Default: 0.

  • int install_signal_handlers

    Install Python signal handlers?

    Default: 1 in Python mode, 0 in isolated mode.

  • int interactive

    If greater than 0, enable the interactive mode (REPL).

    Incremented by the -i command line option.

    Default: 0.

  • int isolated

    If greater than 0, enable isolated mode:

    • sys.path contains neither the script’s directory (computed from argv[0] or the current directory) nor the user’s site-packages directory.

    • Python REPL doesn’t import readline nor enable default readline configuration on interactive prompts.

    • Set use_environment and user_site_directory to 0.

    Default: 0 in Python mode, 1 in isolated mode.

    See also PyPreConfig.isolated.

  • int legacy_windows_stdio

    If non-zero, use io.FileIO instead of io.WindowsConsoleIO for sys.stdin, sys.stdout and sys.stderr.

    Set to 1 if the PYTHONLEGACYWINDOWSSTDIO environment variable is set to a non-empty string.

    Only available on Windows. #ifdef MS_WINDOWS macro can be used for Windows specific code.

    Default: 0.

    See also the PEP 528 (Change Windows console encoding to UTF-8).

  • int malloc_stats

    If non-zero, dump statistics on Python pymalloc memory allocator at exit.

    Set to 1 by the PYTHONMALLOCSTATS environment variable.

    The option is ignored if Python is configured using the --without-pymalloc option.

    Default: 0.

  • wchar_t *platlibdir

    Platform library directory name: sys.platlibdir.

    Set by the PYTHONPLATLIBDIR environment variable.

    Default: value of the PLATLIBDIR macro which is set by the configure --with-platlibdir option (default: "lib").

    Part of the Python Path Configuration input.

    3.9 新版功能.

  • wchar_t *pythonpath_env

    Module search paths (sys.path) as a string separated by DELIM (os.path.pathsep).

    Set by the PYTHONPATH environment variable.

    Default: NULL.

    Part of the Python Path Configuration input.

  • PyWideStringList module_search_paths

  • int module_search_paths_set

    Module search paths: sys.path.

    If module_search_paths_set is equal to 0, the function calculating the Python Path Configuration overrides the module_search_paths and sets module_search_paths_set to 1.

    Default: empty list (module_search_paths) and 0 (module_search_paths_set).

    Part of the Python Path Configuration output.

  • int optimization_level

    Compilation optimization level:

    • 0: Peephole optimizer, set __debug__ to True.

    • 1: Level 0, remove assertions, set __debug__ to False.

    • 2: Level 1, strip docstrings.

    Incremented by the -O command line option. Set to the PYTHONOPTIMIZE environment variable value.

    Default: 0.

  • PyWideStringList orig_argv

    The list of the original command line arguments passed to the Python executable: sys.orig_argv.

    If orig_argv list is empty and argv is not a list only containing an empty string, PyConfig_Read() copies argv into orig_argv before modifying argv (if parse_argv is non-zero).

    See also the argv member and the Py_GetArgcArgv() function.

    Default: empty list.

    3.10 新版功能.

  • int parse_argv

    Parse command line arguments?

    If equals to 1, parse argv the same way the regular Python parses command line arguments, and strip Python arguments from argv.

    The PyConfig_Read() function only parses PyConfig.argv arguments once: PyConfig.parse_argv is set to 2 after arguments are parsed. Since Python arguments are strippped from PyConfig.argv, parsing arguments twice would parse the application options as Python options.

    Default: 1 in Python mode, 0 in isolated mode.

    在 3.10 版更改: The PyConfig.argv arguments are now only parsed if PyConfig.parse_argv equals to 1.

  • int parser_debug

    Parser debug mode. If greater than 0, turn on parser debugging output (for expert only, depending on compilation options).

    Incremented by the -d command line option. Set to the PYTHONDEBUG environment variable value.

    Default: 0.

  • int pathconfig_warnings

    On Unix, if non-zero, calculating the Python Path Configuration can log warnings into stderr. If equals to 0, suppress these warnings.

    It has no effect on Windows.

    Default: 1 in Python mode, 0 in isolated mode.

    Part of the Python Path Configuration input.

  • wchar_t *prefix

    The site-specific directory prefix where the platform independent Python files are installed: sys.prefix.

    Default: NULL.

    Part of the Python Path Configuration output.

  • wchar_t *program_name

    Program name used to initialize executable and in early error messages during Python initialization.

    • If Py_SetProgramName() has been called, use its argument.

    • On macOS, use PYTHONEXECUTABLE environment variable if set.

    • If the WITH_NEXT_FRAMEWORK macro is defined, use __PYVENV_LAUNCHER__ environment variable if set.

    • Use argv[0] of argv if available and non-empty.

    • Otherwise, use L"python" on Windows, or L"python3" on other platforms.

    Default: NULL.

    Part of the Python Path Configuration input.

  • wchar_t *pycache_prefix

    Directory where cached .pyc files are written: sys.pycache_prefix.

    Set by the -X pycache_prefix=PATH command line option and the PYTHONPYCACHEPREFIX environment variable.

    If NULL, sys.pycache_prefix is set to None.

    Default: NULL.

  • int quiet

    Quiet mode. If greater than 0, don’t display the copyright and version at Python startup in interactive mode.

    Incremented by the -q command line option.

    Default: 0.

  • wchar_t *run_command

    Value of the -c command line option.

    Used by Py_RunMain().

    Default: NULL.

  • wchar_t *run_filename

    Filename passed on the command line: trailing command line argument without -c or -m.

    For example, it is set to script.py by the python3 script.py arg command.

    Used by Py_RunMain().

    Default: NULL.

  • wchar_t *run_module

    Value of the -m command line option.

    Used by Py_RunMain().

    Default: NULL.

  • int show_ref_count

    Show total reference count at exit?

    Set to 1 by -X showrefcount command line option.

    Need a debug build of Python (the Py_REF_DEBUG macro must be defined).

    Default: 0.

  • int site_import

    Import the site module at startup?

    If equal to zero, disable the import of the module site and the site-dependent manipulations of sys.path that it entails.

    Also disable these manipulations if the site module is explicitly imported later (call site.main() if you want them to be triggered).

    Set to 0 by the -S command line option.

    sys.flags.no_site is set to the inverted value of site_import.

    Default: 1.

  • int skip_source_first_line

    If non-zero, skip the first line of the PyConfig.run_filename source.

    It allows the usage of non-Unix forms of #!cmd. This is intended for a DOS specific hack only.

    Set to 1 by the -x command line option.

    Default: 0.

  • wchar_t *stdio_encoding

  • wchar_t *stdio_errors

    Encoding and encoding errors of sys.stdin, sys.stdout and sys.stderr (but sys.stderr always uses "backslashreplace" error handler).

    If Py_SetStandardStreamEncoding() has been called, use its error and errors arguments if they are not NULL.

    Use the PYTHONIOENCODING environment variable if it is non-empty.

    Default encoding:

    Default error handler:

    • On Windows: use "surrogateescape".

    • "surrogateescape" if PyPreConfig.utf8_mode is non-zero, or if the LC_CTYPE locale is “C” or “POSIX”.

    • "strict" otherwise.

  • int tracemalloc

    Enable tracemalloc?

    If non-zero, call tracemalloc.start() at startup.

    Set by -X tracemalloc=N command line option and by the PYTHONTRACEMALLOC environment variable.

    Default: -1 in Python mode, 0 in isolated mode.

  • int use_environment

    Use environment variables?

    If equals to zero, ignore the environment variables.

    Default: 1 in Python config and 0 in isolated config.

  • int user_site_directory

    If non-zero, add the user site directory to sys.path.

    Set to 0 by the -s and -I command line options.

    Set to 0 by the PYTHONNOUSERSITE environment variable.

    Default: 1 in Python mode, 0 in isolated mode.

  • int verbose

    Verbose mode. If greater than 0, print a message each time a module is imported, showing the place (filename or built-in module) from which it is loaded.

    If greater or equal to 2, print a message for each file that is checked for when searching for a module. Also provides information on module cleanup at exit.

    Incremented by the -v command line option.

    Set to the PYTHONVERBOSE environment variable value.

    Default: 0.

  • PyWideStringList warnoptions

    Options of the warnings module to build warnings filters, lowest to highest priority: sys.warnoptions.

    The warnings module adds sys.warnoptions in the reverse order: the last PyConfig.warnoptions item becomes the first item of warnings.filters which is checked first (highest priority).

    The -W command line options adds its value to warnoptions, it can be used multiple times.

    The PYTHONWARNINGS environment variable can also be used to add warning options. Multiple options can be specified, separated by commas (,).

    Default: empty list.

  • int write_bytecode

    If equal to 0, Python won’t try to write .pyc files on the import of source modules.

    Set to 0 by the -B command line option and the PYTHONDONTWRITEBYTECODE environment variable.

    sys.dont_write_bytecode is initialized to the inverted value of write_bytecode.

    Default: 1.

  • PyWideStringList xoptions

    Values of the -X command line options: sys._xoptions.

    Default: empty list.

If parse_argv is non-zero, argv arguments are parsed the same way the regular Python parses command line arguments, and Python arguments are stripped from argv.

The xoptions options are parsed to set other options: see the -X command line option.

在 3.9 版更改: The show_alloc_count field has been removed.

Initialization with PyConfig

Function to initialize Python:

PyStatus Py_InitializeFromConfig(const PyConfig *config)

Initialize Python from config configuration.

The caller is responsible to handle exceptions (error or exit) using PyStatus_Exception() and Py_ExitStatusException().

If PyImport_FrozenModules(), PyImport_AppendInittab() or PyImport_ExtendInittab() are used, they must be set or called after Python preinitialization and before the Python initialization. If Python is initialized multiple times, PyImport_AppendInittab() or PyImport_ExtendInittab() must be called before each Python initialization.

The current configuration (PyConfig type) is stored in PyInterpreterState.config.

Example setting the program name:

  1. void init_python(void)
  2. {
  3.     PyStatus status;
  5.     PyConfig config;
  6.     PyConfig_InitPythonConfig(&config);
  8.     /* Set the program name. Implicitly preinitialize Python. */
  9.     status = PyConfig_SetString(&config, &config.program_name,
  10.                                 L"/path/to/my_program");
  11.     if (PyStatus_Exception(status)) {
  12.         goto exception;
  13.     }
  15.     status = Py_InitializeFromConfig(&config);
  16.     if (PyStatus_Exception(status)) {
  17.         goto exception;
  18.     }
  19.     PyConfig_Clear(&config);
  20.     return;
  22. exception:
  23.     PyConfig_Clear(&config);
  24.     Py_ExitStatusException(status);
  25. }

More complete example modifying the default configuration, read the configuration, and then override some parameters:

  1. PyStatus init_python(const char *program_name)
  2. {
  3.     PyStatus status;
  5.     PyConfig config;
  6.     PyConfig_InitPythonConfig(&config);
  8.     /* Set the program name before reading the configuration
  9.        (decode byte string from the locale encoding).
  11.        Implicitly preinitialize Python. */
  12.     status = PyConfig_SetBytesString(&config, &config.program_name,
  13.                                      program_name);
  14.     if (PyStatus_Exception(status)) {
  15.         goto done;
  16.     }
  18.     /* Read all configuration at once */
  19.     status = PyConfig_Read(&config);
  20.     if (PyStatus_Exception(status)) {
  21.         goto done;
  22.     }
  24.     /* Append our custom search path to sys.path */
  25.     status = PyWideStringList_Append(&config.module_search_paths,
  26.                                      L"/path/to/more/modules");
  27.     if (PyStatus_Exception(status)) {
  28.         goto done;
  29.     }
  31.     /* Override executable computed by PyConfig_Read() */
  32.     status = PyConfig_SetString(&config, &config.executable,
  33.                                 L"/path/to/my_executable");
  34.     if (PyStatus_Exception(status)) {
  35.         goto done;
  36.     }
  38.     status = Py_InitializeFromConfig(&config);
  40. done:
  41.     PyConfig_Clear(&config);
  42.     return status;
  43. }

Isolated Configuration

PyPreConfig_InitIsolatedConfig() and PyConfig_InitIsolatedConfig() functions create a configuration to isolate Python from the system. For example, to embed Python into an application.

This configuration ignores global configuration variables, environments variables, command line arguments (PyConfig.argv is not parsed) and user site directory. The C standard streams (ex: stdout) and the LC_CTYPE locale are left unchanged. Signal handlers are not installed.

Configuration files are still used with this configuration. Set the Python Path Configuration (“output fields”) to ignore these configuration files and avoid the function computing the default path configuration.

Python Configuration

PyPreConfig_InitPythonConfig() and PyConfig_InitPythonConfig() functions create a configuration to build a customized Python which behaves as the regular Python.

Environments variables and command line arguments are used to configure Python, whereas global configuration variables are ignored.

This function enables C locale coercion (PEP 538) and Python UTF-8 Mode (PEP 540) depending on the LC_CTYPE locale, PYTHONUTF8 and PYTHONCOERCECLOCALE environment variables.

Python Path Configuration

PyConfig contains multiple fields for the path configuration:

If at least one “output field” is not set, Python calculates the path configuration to fill unset fields. If module_search_paths_set is equal to 0, module_search_paths is overridden and module_search_paths_set is set to 1.

It is possible to completely ignore the function calculating the default path configuration by setting explicitly all path configuration output fields listed above. A string is considered as set even if it is non-empty. module_search_paths is considered as set if module_search_paths_set is set to 1. In this case, path configuration input fields are ignored as well.

Set pathconfig_warnings to 0 to suppress warnings when calculating the path configuration (Unix only, Windows does not log any warning).

If base_prefix or base_exec_prefix fields are not set, they inherit their value from prefix and exec_prefix respectively.

Py_RunMain() and Py_Main() modify sys.path:

If site_import is non-zero, sys.path can be modified by the site module. If user_site_directory is non-zero and the user’s site-package directory exists, the site module appends the user’s site-package directory to sys.path.

The following configuration files are used by the path configuration:

  • pyvenv.cfg

  • python._pth (仅Windows)

  • pybuilddir.txt (仅Unix)

The __PYVENV_LAUNCHER__ environment variable is used to set PyConfig.base_executable

Py_RunMain()

int Py_RunMain(void)

Execute the command (PyConfig.run_command), the script (PyConfig.run_filename) or the module (PyConfig.run_module) specified on the command line or in the configuration.

By default and when if -i option is used, run the REPL.

Finally, finalizes Python and returns an exit status that can be passed to the exit() function.

See Python Configuration for an example of customized Python always running in isolated mode using Py_RunMain().

Py_GetArgcArgv()

void Py_GetArgcArgv(int argc, wchar_t *argv*)

Get the original command line arguments, before Python modified them.

See also PyConfig.orig_argv member.

Multi-Phase Initialization Private Provisional API

This section is a private provisional API introducing multi-phase initialization, the core feature of the PEP 432:

  • “Core” initialization phase, “bare minimum Python”:

    • Builtin types;

    • Builtin exceptions;

    • Builtin and frozen modules;

    • The sys module is only partially initialized (ex: sys.path doesn’t exist yet).

  • “Main” initialization phase, Python is fully initialized:

私有临时API：

  • PyConfig._init_main: if set to 0, Py_InitializeFromConfig() stops at the “Core” initialization phase.

  • PyConfig._isolated_interpreter: if non-zero, disallow threads, subprocesses and fork.

PyStatus _Py_InitializeMain(void)

Move to the “Main” initialization phase, finish the Python initialization.

No module is imported during the “Core” phase and the importlib module is not configured: the Path Configuration is only applied during the “Main” phase. It may allow to customize Python in Python to override or tune the Path Configuration, maybe install a custom sys.meta_path importer or an import hook, etc.

It may become possible to calculatin the Path Configuration in Python, after the Core phase and before the Main phase, which is one of the PEP 432 motivation.

The “Core” phase is not properly defined: what should be and what should not be available at this phase is not specified yet. The API is marked as private and provisional: the API can be modified or even be removed anytime until a proper public API is designed.

Example running Python code between “Core” and “Main” initialization phases:

  1. void init_python(void)
  2. {
  3.     PyStatus status;
  5.     PyConfig config;
  6.     PyConfig_InitPythonConfig(&config);
  7.     config._init_main = 0;
  9.     /* ... customize 'config' configuration ... */
  11.     status = Py_InitializeFromConfig(&config);
  12.     PyConfig_Clear(&config);
  13.     if (PyStatus_Exception(status)) {
  14.         Py_ExitStatusException(status);
  15.     }
  17.     /* Use sys.stderr because sys.stdout is only created
  18.        by _Py_InitializeMain() */
  19.     int res = PyRun_SimpleString(
  20.         "import sys; "
  21.         "print('Run Python code before _Py_InitializeMain', "
  22.                "file=sys.stderr)");
  23.     if (res < 0) {
  24.         exit(1);
  25.     }
  27.     /* ... put more configuration code here ... */
  29.     status = _Py_InitializeMain();
  30.     if (PyStatus_Exception(status)) {
  31.         Py_ExitStatusException(status);
  32.     }
  33. }