mirrors/cpython
1
0
Fork 0
mirror of https://github.com/python/cpython.git synced 2025-08-04 17:08:35 +00:00
Code Issues Projects Releases Packages Wiki Activity Actions 13
cpython/Doc/c-api/init_config.rst
Victor Stinner bdace21b76 bpo-38304: Remove PyConfig.struct_size (GH-16500) 
For now, we'll rely on the fact that the config structures aren't covered by the stable ABI.

We may revisit this in the future if we further explore the idea of offering a stable embedding API.
2019-10-01 08:46:42 +10:00

1071 lines
33 KiB
ReStructuredText
Raw Blame History

.. highlight:: c
.. _init-config:
***********************************
Python Initialization Configuration
***********************************
.. versionadded:: 3.8
Structures:
* :c:type:`PyConfig`
* :c:type:`PyPreConfig`
* :c:type:`PyStatus`
* :c:type:`PyWideStringList`
Functions:
* :c:func:`PyConfig_Clear`
* :c:func:`PyConfig_InitIsolatedConfig`
* :c:func:`PyConfig_InitPythonConfig`
* :c:func:`PyConfig_Read`
* :c:func:`PyConfig_SetArgv`
* :c:func:`PyConfig_SetBytesArgv`
* :c:func:`PyConfig_SetBytesString`
* :c:func:`PyConfig_SetString`
* :c:func:`PyConfig_SetWideStringList`
* :c:func:`PyPreConfig_InitIsolatedConfig`
* :c:func:`PyPreConfig_InitPythonConfig`
* :c:func:`PyStatus_Error`
* :c:func:`PyStatus_Exception`
* :c:func:`PyStatus_Exit`
* :c:func:`PyStatus_IsError`
* :c:func:`PyStatus_IsExit`
* :c:func:`PyStatus_NoMemory`
* :c:func:`PyStatus_Ok`
* :c:func:`PyWideStringList_Append`
* :c:func:`PyWideStringList_Insert`
* :c:func:`Py_ExitStatusException`
* :c:func:`Py_InitializeFromConfig`
* :c:func:`Py_PreInitialize`
* :c:func:`Py_PreInitializeFromArgs`
* :c:func:`Py_PreInitializeFromBytesArgs`
* :c:func:`Py_RunMain`
The preconfiguration (``PyPreConfig`` type) is stored in
``_PyRuntime.preconfig`` and the configuration (``PyConfig`` type) is stored in
``PyInterpreterState.config``.
See also :ref:`Initialization, Finalization, and Threads <initialization>`.
.. seealso::
:pep:`587` "Python Initialization Configuration".
PyWideStringList
----------------
.. c:type:: PyWideStringList
List of ``wchar_t*`` strings.
If *length* is non-zero, *items* must be non-NULL and all strings must be
non-NULL.
Methods:
.. c:function:: PyStatus PyWideStringList_Append(PyWideStringList *list, const wchar_t *item)
Append *item* to *list*.
Python must be preinitialized to call this function.
.. c: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:
.. c:member:: Py_ssize_t length
List length.
.. c:member:: wchar_t** items
List items.
PyStatus
--------
.. c: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:
.. c:member:: int exitcode
Exit code. Argument passed to ``exit()``.
.. c:member:: const char *err_msg
Error message.
.. c:member:: const char *func
Name of the function which created an error, can be ``NULL``.
Functions to create a status:
.. c:function:: PyStatus PyStatus_Ok(void)
Success.
.. c:function:: PyStatus PyStatus_Error(const char *err_msg)
Initialization error with a message.
.. c:function:: PyStatus PyStatus_NoMemory(void)
Memory allocation failure (out of memory).
.. c:function:: PyStatus PyStatus_Exit(int exitcode)
Exit Python with the specified exit code.
Functions to handle a status:
.. c:function:: int PyStatus_Exception(PyStatus status)
Is the status an error or an exit? If true, the exception must be
handled; by calling :c:func:`Py_ExitStatusException` for example.
.. c:function:: int PyStatus_IsError(PyStatus status)
Is the result an error?
.. c:function:: int PyStatus_IsExit(PyStatus status)
Is the result an exit?
.. c:function:: 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.
.. note::
Internally, Python uses macros which set ``PyStatus.func``,
whereas functions to create a status set ``func`` to ``NULL``.
Example::
PyStatus alloc(void **ptr, size_t size)
{
*ptr = PyMem_RawMalloc(size);
if (*ptr == NULL) {
return PyStatus_NoMemory();
}
return PyStatus_Ok();
}
int main(int argc, char **argv)
{
void *ptr;
PyStatus status = alloc(&ptr, 16);
if (PyStatus_Exception(status)) {
Py_ExitStatusException(status);
}
PyMem_Free(ptr);
return 0;
}
PyPreConfig
-----------
.. c:type:: PyPreConfig
Structure used to preinitialize Python:
* Set the Python memory allocator
* Configure the LC_CTYPE locale
* Set the UTF-8 mode
Function to initialize a preconfiguration:
.. c:function:: void PyPreConfig_InitIsolatedConfig(PyPreConfig *preconfig)
Initialize the preconfiguration with :ref:`Python Configuration
<init-python-config>`.
.. c:function:: void PyPreConfig_InitPythonConfig(PyPreConfig *preconfig)
Initialize the preconfiguration with :ref:`Isolated Configuration
<init-isolated-conf>`.
Structure fields:
.. c:member:: int allocator
Name of the memory allocator:
* ``PYMEM_ALLOCATOR_NOT_SET`` (``0``): don't change memory allocators
(use defaults)
* ``PYMEM_ALLOCATOR_DEFAULT`` (``1``): default memory allocators
* ``PYMEM_ALLOCATOR_DEBUG`` (``2``): default memory allocators with
debug hooks
* ``PYMEM_ALLOCATOR_MALLOC`` (``3``): force usage of ``malloc()``
* ``PYMEM_ALLOCATOR_MALLOC_DEBUG`` (``4``): force usage of
``malloc()`` with debug hooks
* ``PYMEM_ALLOCATOR_PYMALLOC`` (``5``): :ref:`Python pymalloc memory
allocator <pymalloc>`
* ``PYMEM_ALLOCATOR_PYMALLOC_DEBUG`` (``6``): :ref:`Python pymalloc
memory allocator <pymalloc>` with debug hooks
``PYMEM_ALLOCATOR_PYMALLOC`` and ``PYMEM_ALLOCATOR_PYMALLOC_DEBUG``
are not supported if Python is configured using ``--without-pymalloc``
See :ref:`Memory Management <memory>`.
.. c:member:: int configure_locale
Set the LC_CTYPE locale to the user preferred locale? If equals to 0, set
:c:member:`coerce_c_locale` and :c:member:`coerce_c_locale_warn` to 0.
.. c:member:: int coerce_c_locale
If equals to 2, coerce the C locale; if equals to 1, read the LC_CTYPE
locale to decide if it should be coerced.
.. c:member:: int coerce_c_locale_warn
If non-zero, emit a warning if the C locale is coerced.
.. c:member:: int dev_mode
See :c:member:`PyConfig.dev_mode`.
.. c:member:: int isolated
See :c:member:`PyConfig.isolated`.
.. c:member:: int legacy_windows_fs_encoding (Windows only)
If non-zero, disable UTF-8 Mode, set the Python filesystem encoding to
``mbcs``, set the filesystem error handler to ``replace``.
Only available on Windows. ``#ifdef MS_WINDOWS`` macro can be used for
Windows specific code.
.. c:member:: int parse_argv
If non-zero, :c:func:`Py_PreInitializeFromArgs` and
:c:func:`Py_PreInitializeFromBytesArgs` parse their ``argv`` argument the
same way the regular Python parses command line arguments: see
:ref:`Command Line Arguments <using-on-cmdline>`.
.. c:member:: int use_environment
See :c:member:`PyConfig.use_environment`.
.. c:member:: int utf8_mode
If non-zero, enable the UTF-8 mode.
Preinitialization with PyPreConfig
----------------------------------
Functions to preinitialize Python:
.. c:function:: PyStatus Py_PreInitialize(const PyPreConfig *preconfig)
Preinitialize Python from *preconfig* preconfiguration.
.. c:function:: PyStatus Py_PreInitializeFromBytesArgs(const PyPreConfig *preconfig, int argc, char * const *argv)
Preinitialize Python from *preconfig* preconfiguration and command line
arguments (bytes strings).
.. c:function:: PyStatus Py_PreInitializeFromArgs(const PyPreConfig *preconfig, int argc, wchar_t * const * argv)
Preinitialize Python from *preconfig* preconfiguration and command line
arguments (wide strings).
The caller is responsible to handle exceptions (error or exit) using
:c:func:`PyStatus_Exception` and :c:func:`Py_ExitStatusException`.
For :ref:`Python Configuration <init-python-config>`
(:c:func:`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 :option:`-X utf8 <-X>` command line option
enables the UTF-8 Mode.
``PyMem_SetAllocator()`` can be called after :c:func:`Py_PreInitialize` and
before :c:func:`Py_InitializeFromConfig` to install a custom memory allocator.
It can be called before :c:func:`Py_PreInitialize` if
:c:member:`PyPreConfig.allocator` is set to ``PYMEM_ALLOCATOR_NOT_SET``.
Python memory allocation functions like :c:func:`PyMem_RawMalloc` must not be
used before Python preinitialization, whereas calling directly ``malloc()`` and
``free()`` is always safe. :c:func:`Py_DecodeLocale` must not be called before
the preinitialization.
Example using the preinitialization to enable the UTF-8 Mode::
PyStatus status;
PyPreConfig preconfig;
PyPreConfig_InitPythonConfig(&preconfig);
preconfig.utf8_mode = 1;
status = Py_PreInitialize(&preconfig);
if (PyStatus_Exception(status)) {
Py_ExitStatusException(status);
}
/* at this point, Python will speak UTF-8 */
Py_Initialize();
/* ... use Python API here ... */
Py_Finalize();
PyConfig
--------
.. c:type:: PyConfig
Structure containing most parameters to configure Python.
Structure methods:
.. c:function:: PyStatus PyConfig_InitPythonConfig(PyConfig *config)
Initialize configuration with :ref:`Python Configuration
<init-python-config>`.
.. c:function:: PyStatus PyConfig_InitIsolatedConfig(PyConfig *config)
Initialize configuration with :ref:`Isolated Configuration
<init-isolated-conf>`.
.. c:function:: PyStatus PyConfig_SetString(PyConfig *config, wchar_t * const *config_str, const wchar_t *str)
Copy the wide character string *str* into ``*config_str``.
Preinitialize Python if needed.
.. c:function:: PyStatus PyConfig_SetBytesString(PyConfig *config, wchar_t * const *config_str, const char *str)
Decode *str* using ``Py_DecodeLocale()`` and set the result into ``*config_str``.
Preinitialize Python if needed.
.. c:function:: PyStatus PyConfig_SetArgv(PyConfig *config, int argc, wchar_t * const *argv)
Set command line arguments from wide character strings.
Preinitialize Python if needed.
.. c:function:: PyStatus PyConfig_SetBytesArgv(PyConfig *config, int argc, char * const *argv)
Set command line arguments: decode bytes using :c:func:`Py_DecodeLocale`.
Preinitialize Python if needed.
.. c:function:: PyStatus PyConfig_SetWideStringList(PyConfig *config, PyWideStringList *list, Py_ssize_t length, wchar_t **items)
Set the list of wide strings *list* to *length* and *items*.
Preinitialize Python if needed.
.. c:function:: PyStatus PyConfig_Read(PyConfig *config)
Read all Python configuration.
Fields which are already initialized are left unchanged.
Preinitialize Python if needed.
.. c:function:: void PyConfig_Clear(PyConfig *config)
Release configuration memory.
Most ``PyConfig`` methods preinitialize Python if needed. In that case, the
Python preinitialization configuration in based on the :c:type:`PyConfig`.
If configuration fields which are in common with :c:type:`PyPreConfig` are
tuned, they must be set before calling a :c:type:`PyConfig` method:
* :c:member:`~PyConfig.dev_mode`
* :c:member:`~PyConfig.isolated`
* :c:member:`~PyConfig.parse_argv`
* :c:member:`~PyConfig.use_environment`
Moreover, if :c:func:`PyConfig_SetArgv` or :c:func:`PyConfig_SetBytesArgv`
is used, this method must be called first, before other methods, since the
preinitialization configuration depends on command line arguments (if
:c:member:`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:
.. c:member:: PyWideStringList argv
Command line arguments, :data:`sys.argv`. See
:c:member:`~PyConfig.parse_argv` to parse :c:member:`~PyConfig.argv` the
same way the regular Python parses Python command line arguments. If
:c:member:`~PyConfig.argv` is empty, an empty string is added to ensure
that :data:`sys.argv` always exists and is never empty.
.. c:member:: wchar_t* base_exec_prefix
:data:`sys.base_exec_prefix`.
.. c:member:: wchar_t* base_executable
:data:`sys._base_executable`: ``__PYVENV_LAUNCHER__`` environment
variable value, or copy of :c:member:`PyConfig.executable`.
.. c:member:: wchar_t* base_prefix
:data:`sys.base_prefix`.
.. c:member:: int buffered_stdio
If equals to 0, enable unbuffered mode, making the stdout and stderr
streams unbuffered.
stdin is always opened in buffered mode.
.. c:member:: int bytes_warning
If equals to 1, issue a warning when comparing :class:`bytes` or
:class:`bytearray` with :class:`str`, or comparing :class:`bytes` with
:class:`int`. If equal or greater to 2, raise a :exc:`BytesWarning`
exception.
.. c:member:: wchar_t* check_hash_pycs_mode
Control the validation behavior of hash-based ``.pyc`` files (see
:pep:`552`): :option:`--check-hash-based-pycs` command line option value.
Valid values: ``always``, ``never`` and ``default``.
The default value is: ``default``.
.. c:member:: int configure_c_stdio
If non-zero, configure C standard streams (``stdio``, ``stdout``,
``stdout``). For example, set their mode to ``O_BINARY`` on Windows.
.. c:member:: int dev_mode
Development mode: see :option:`-X dev <-X>`.
.. c:member:: int dump_refs
If non-zero, dump all objects which are still alive at exit.
Require a debug build of Python (``Py_REF_DEBUG`` macro must be defined).
.. c:member:: wchar_t* exec_prefix
:data:`sys.exec_prefix`.
.. c:member:: wchar_t* executable
:data:`sys.executable`.
.. c:member:: int faulthandler
If non-zero, call :func:`faulthandler.enable` at startup.
.. c:member:: wchar_t* filesystem_encoding
Filesystem encoding, :func:`sys.getfilesystemencoding`.
.. c:member:: wchar_t* filesystem_errors
Filesystem encoding errors, :func:`sys.getfilesystemencodeerrors`.
.. c:member:: unsigned long hash_seed
.. c:member:: int use_hash_seed
Randomized hash function seed.
If :c:member:`~PyConfig.use_hash_seed` is zero, a seed is chosen randomly
at Pythonstartup, and :c:member:`~PyConfig.hash_seed` is ignored.
.. c:member:: wchar_t* home
Python home directory.
Initialized from :envvar:`PYTHONHOME` environment variable value by
default.
.. c:member:: int import_time
If non-zero, profile import time.
.. c:member:: int inspect
Enter interactive mode after executing a script or a command.
.. c:member:: int install_signal_handlers
Install signal handlers?
.. c:member:: int interactive
Interactive mode.
.. c:member:: int isolated
If greater than 0, enable isolated mode:
* :data:`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 :mod:`readline` nor enable default readline
configuration on interactive prompts.
* Set :c:member:`~PyConfig.use_environment` and
:c:member:`~PyConfig.user_site_directory` to 0.
.. c:member:: int legacy_windows_stdio
If non-zero, use :class:`io.FileIO` instead of
:class:`io.WindowsConsoleIO` for :data:`sys.stdin`, :data:`sys.stdout`
and :data:`sys.stderr`.
Only available on Windows. ``#ifdef MS_WINDOWS`` macro can be used for
Windows specific code.
.. c:member:: int malloc_stats
If non-zero, dump statistics on :ref:`Python pymalloc memory allocator
<pymalloc>` at exit.
The option is ignored if Python is built using ``--without-pymalloc``.
.. c:member:: wchar_t* pythonpath_env
Module search paths as a string separated by ``DELIM``
(:data:`os.path.pathsep`).
Initialized from :envvar:`PYTHONPATH` environment variable value by
default.
.. c:member:: PyWideStringList module_search_paths
.. c:member:: int module_search_paths_set
:data:`sys.path`. If :c:member:`~PyConfig.module_search_paths_set` is
equal to 0, the :c:member:`~PyConfig.module_search_paths` is overridden
by the function calculating the :ref:`Path Configuration
<init-path-config>`.
.. c:member:: int optimization_level
Compilation optimization level:
* 0: Peephole optimizer (and ``__debug__`` is set to ``True``)
* 1: Remove assertions, set ``__debug__`` to ``False``
* 2: Strip docstrings
.. c:member:: int parse_argv
If non-zero, parse :c:member:`~PyConfig.argv` the same way the regular
Python command line arguments, and strip Python arguments from
:c:member:`~PyConfig.argv`: see :ref:`Command Line Arguments
<using-on-cmdline>`.
.. c:member:: int parser_debug
If non-zero, turn on parser debugging output (for expert only, depending
on compilation options).
.. c:member:: int pathconfig_warnings
If equal to 0, suppress warnings when calculating the :ref:`Path
Configuration <init-path-config>` (Unix only, Windows does not log any
warning). Otherwise, warnings are written into ``stderr``.
.. c:member:: wchar_t* prefix
:data:`sys.prefix`.
.. c:member:: wchar_t* program_name
Program name. Used to initialize :c:member:`~PyConfig.executable`, and in
early error messages.
.. c:member:: wchar_t* pycache_prefix
:data:`sys.pycache_prefix`: ``.pyc`` cache prefix.
If NULL, :data:`sys.pycache_prefix` is set to ``None``.
.. c:member:: int quiet
Quiet mode. For example, don't display the copyright and version messages
in interactive mode.
.. c:member:: wchar_t* run_command
``python3 -c COMMAND`` argument. Used by :c:func:`Py_RunMain`.
.. c:member:: wchar_t* run_filename
``python3 FILENAME`` argument. Used by :c:func:`Py_RunMain`.
.. c:member:: wchar_t* run_module
``python3 -m MODULE`` argument. Used by :c:func:`Py_RunMain`.
.. c:member:: int show_alloc_count
Show allocation counts at exit?
Set to 1 by :option:`-X showalloccount <-X>` command line option.
Need a special Python build with ``COUNT_ALLOCS`` macro defined.
.. c:member:: int show_ref_count
Show total reference count at exit?
Set to 1 by :option:`-X showrefcount <-X>` command line option.
Need a debug build of Python (``Py_REF_DEBUG`` macro must be defined).
.. c:member:: int site_import
Import the :mod:`site` module at startup?
.. c:member:: int skip_source_first_line
Skip the first line of the source?
.. c:member:: wchar_t* stdio_encoding
.. c:member:: wchar_t* stdio_errors
Encoding and encoding errors of :data:`sys.stdin`, :data:`sys.stdout` and
:data:`sys.stderr`.
.. c:member:: int tracemalloc
If non-zero, call :func:`tracemalloc.start` at startup.
.. c:member:: int use_environment
If greater than 0, use :ref:`environment variables <using-on-envvars>`.
.. c:member:: int user_site_directory
If non-zero, add user site directory to :data:`sys.path`.
.. c:member:: int verbose
If non-zero, enable verbose mode.
.. c:member:: PyWideStringList warnoptions
:data:`sys.warnoptions`: options of the :mod:`warnings` module to build
warnings filters: lowest to highest priority.
The :mod:`warnings` module adds :data:`sys.warnoptions` in the reverse
order: the last :c:member:`PyConfig.warnoptions` item becomes the first
item of :data:`warnings.filters` which is checked first (highest
priority).
.. c:member:: int write_bytecode
If non-zero, write ``.pyc`` files.
:data:`sys.dont_write_bytecode` is initialized to the inverted value of
:c:member:`~PyConfig.write_bytecode`.
.. c:member:: PyWideStringList xoptions
:data:`sys._xoptions`.
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``: see :ref:`Command Line Arguments
<using-on-cmdline>`.
The ``xoptions`` options are parsed to set other options: see :option:`-X`
option.
Initialization with PyConfig
----------------------------
Function to initialize Python:
.. c:function:: PyStatus Py_InitializeFromConfig(const PyConfig *config)
Initialize Python from *config* configuration.
The caller is responsible to handle exceptions (error or exit) using
:c:func:`PyStatus_Exception` and :c:func:`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.
Example setting the program name::
void init_python(void)
{
PyStatus status;
PyConfig config;
status = PyConfig_InitPythonConfig(&config);
if (PyStatus_Exception(status)) {
goto fail;
}
/* Set the program name. Implicitly preinitialize Python. */
status = PyConfig_SetString(&config, &config.program_name,
L"/path/to/my_program");
if (PyStatus_Exception(status)) {
goto fail;
}
status = Py_InitializeFromConfig(&config);
if (PyStatus_Exception(status)) {
goto fail;
}
PyConfig_Clear(&config);
return;
fail:
PyConfig_Clear(&config);
Py_ExitStatusException(status);
}
More complete example modifying the default configuration, read the
configuration, and then override some parameters::
PyStatus init_python(const char *program_name)
{
PyStatus status;
PyConfig config;
status = PyConfig_InitPythonConfig(&config);
if (PyStatus_Exception(status)) {
goto done;
}
/* Set the program name before reading the configuraton
(decode byte string from the locale encoding).
Implicitly preinitialize Python. */
status = PyConfig_SetBytesString(&config, &config.program_name,
program_name);
if (PyStatus_Exception(status)) {
goto done;
}
/* Read all configuration at once */
status = PyConfig_Read(&config);
if (PyStatus_Exception(status)) {
goto done;
}
/* Append our custom search path to sys.path */
status = PyWideStringList_Append(&config.module_search_paths,
L"/path/to/more/modules");
if (PyStatus_Exception(status)) {
goto done;
}
/* Override executable computed by PyConfig_Read() */
status = PyConfig_SetString(&config, &config.executable,
L"/path/to/my_executable");
if (PyStatus_Exception(status)) {
goto done;
}
status = Py_InitializeFromConfig(&config);
done:
PyConfig_Clear(&config);
return status;
}
.. _init-isolated-conf:
Isolated Configuration
----------------------
:c:func:`PyPreConfig_InitIsolatedConfig` and
:c:func:`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 (:c:member:`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
:ref:`Path Configuration <init-path-config>` ("output fields") to ignore these
configuration files and avoid the function computing the default path
configuration.
.. _init-python-config:
Python Configuration
--------------------
:c:func:`PyPreConfig_InitPythonConfig` and :c:func:`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 UTF-8 Mode
(:pep:`540`) depending on the LC_CTYPE locale, :envvar:`PYTHONUTF8` and
:envvar:`PYTHONCOERCECLOCALE` environment variables.
Example of customized Python always running in isolated mode::
int main(int argc, char **argv)
{
PyStatus status;
PyConfig config;
status = PyConfig_InitPythonConfig(&config);
if (PyStatus_Exception(status)) {
goto fail;
}
config.isolated = 1;
/* Decode command line arguments.
Implicitly preinitialize Python (in isolated mode). */
status = PyConfig_SetBytesArgv(&config, argc, argv);
if (PyStatus_Exception(status)) {
goto fail;
}
status = Py_InitializeFromConfig(&config);
if (PyStatus_Exception(status)) {
goto fail;
}
PyConfig_Clear(&config);
return Py_RunMain();
fail:
PyConfig_Clear(&config);
if (PyStatus_IsExit(status)) {
return status.exitcode;
}
/* Display the error message and exit the process with
non-zero exit code */
Py_ExitStatusException(status);
}
.. _init-path-config:
Path Configuration
------------------
:c:type:`PyConfig` contains multiple fields for the path configuration:
* Path configuration inputs:
* :c:member:`PyConfig.home`
* :c:member:`PyConfig.pathconfig_warnings`
* :c:member:`PyConfig.program_name`
* :c:member:`PyConfig.pythonpath_env`
* current working directory: to get absolute paths
* ``PATH`` environment variable to get the program full path
(from :c:member:`PyConfig.program_name`)
* ``__PYVENV_LAUNCHER__`` environment variable
* (Windows only) Application paths in the registry under
"Software\Python\PythonCore\X.Y\PythonPath" of HKEY_CURRENT_USER and
HKEY_LOCAL_MACHINE (where X.Y is the Python version).
* Path configuration output fields:
* :c:member:`PyConfig.base_exec_prefix`
* :c:member:`PyConfig.base_executable`
* :c:member:`PyConfig.base_prefix`
* :c:member:`PyConfig.exec_prefix`
* :c:member:`PyConfig.executable`
* :c:member:`PyConfig.module_search_paths_set`,
:c:member:`PyConfig.module_search_paths`
* :c:member:`PyConfig.prefix`
If at least one "output field" is not set, Python calculates the path
configuration to fill unset fields. If
:c:member:`~PyConfig.module_search_paths_set` is equal to 0,
:c:member:`~PyConfig.module_search_paths` is overridden and
:c:member:`~PyConfig.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 :c:member:`~PyConfig.pathconfig_warnings` to 0 to suppress warnings when
calculating the path configuration (Unix only, Windows does not log any warning).
If :c:member:`~PyConfig.base_prefix` or :c:member:`~PyConfig.base_exec_prefix`
fields are not set, they inherit their value from :c:member:`~PyConfig.prefix`
and :c:member:`~PyConfig.exec_prefix` respectively.
:c:func:`Py_RunMain` and :c:func:`Py_Main` modify :data:`sys.path`:
* If :c:member:`~PyConfig.run_filename` is set and is a directory which contains a
``__main__.py`` script, prepend :c:member:`~PyConfig.run_filename` to
:data:`sys.path`.
* If :c:member:`~PyConfig.isolated` is zero:
* If :c:member:`~PyConfig.run_module` is set, prepend the current directory
to :data:`sys.path`. Do nothing if the current directory cannot be read.
* If :c:member:`~PyConfig.run_filename` is set, prepend the directory of the
filename to :data:`sys.path`.
* Otherwise, prepend an empty string to :data:`sys.path`.
If :c:member:`~PyConfig.site_import` is non-zero, :data:`sys.path` can be
modified by the :mod:`site` module. If
:c:member:`~PyConfig.user_site_directory` is non-zero and the user's
site-package directory exists, the :mod:`site` module appends the user's
site-package directory to :data:`sys.path`.
The following configuration files are used by the path configuration:
* ``pyvenv.cfg``
* ``python._pth`` (Windows only)
* ``pybuilddir.txt`` (Unix only)
The ``__PYVENV_LAUNCHER__`` environment variable is used to set
:c:member:`PyConfig.base_executable`
Py_RunMain()
------------
.. c:function:: int Py_RunMain(void)
Execute the command (:c:member:`PyConfig.run_command`), the script
(:c:member:`PyConfig.run_filename`) or the module
(:c:member:`PyConfig.run_module`) specified on the command line or in the
configuration.
By default and when if :option:`-i` option is used, run the REPL.
Finally, finalizes Python and returns an exit status that can be passed to
the ``exit()`` function.
See :ref:`Python Configuration <init-python-config>` for an example of
customized Python always running in isolated mode using
:c:func:`Py_RunMain`.
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 :mod:`sys` module is only partially initialized
(ex: :data:`sys.path` doesn't exist yet).
* "Main" initialization phase, Python is fully initialized:
* Install and configure :mod:`importlib`;
* Apply the :ref:`Path Configuration <init-path-config>`;
* Install signal handlers;
* Finish :mod:`sys` module initialization (ex: create :data:`sys.stdout`
and :data:`sys.path`);
* Enable optional features like :mod:`faulthandler` and :mod:`tracemalloc`;
* Import the :mod:`site` module;
* etc.
Private provisional API:
* :c:member:`PyConfig._init_main`: if set to 0,
:c:func:`Py_InitializeFromConfig` stops at the "Core" initialization phase.
.. c:function:: 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 :ref:`Path Configuration <init-path-config>` is only
applied during the "Main" phase. It may allow to customize Python in Python to
override or tune the :ref:`Path Configuration <init-path-config>`, maybe
install a custom :data:`sys.meta_path` importer or an import hook, etc.
It may become possible to calculatin the :ref:`Path Configuration
<init-path-config>` 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::
void init_python(void)
{
PyStatus status;
PyConfig config;
status = PyConfig_InitPythonConfig(&config);
if (PyStatus_Exception(status)) {
PyConfig_Clear(&config);
Py_ExitStatusException(status);
}
config._init_main = 0;
/* ... customize 'config' configuration ... */
status = Py_InitializeFromConfig(&config);
PyConfig_Clear(&config);
if (PyStatus_Exception(status)) {
Py_ExitStatusException(status);
}
/* Use sys.stderr because sys.stdout is only created
by _Py_InitializeMain() */
int res = PyRun_SimpleString(
"import sys; "
"print('Run Python code before _Py_InitializeMain', "
"file=sys.stderr)");
if (res < 0) {
exit(1);
}
/* ... put more configuration code here ... */
status = _Py_InitializeMain();
if (PyStatus_Exception(status)) {
Py_ExitStatusException(status);
}
}
Reference in a new issue View git blame Copy permalink