Configuração de Inicialização do Python

Adicionado na versão 3.8.

Python pode ser inicializado com Py_InitializeFromConfig() e a estrutura PyConfig. Pode ser pré-inicializado com Py_PreInitialize() e a estrutura PyPreConfig.

Existem dois tipos de configuração:

  • A Python Configuration pode ser usada para construir um Python personalizado que se comporta como um Python comum. Por exemplo, variáveis de ambiente e argumento de linha de comando são usados para configurar Python.

  • A Configuração isolada pode ser usada para incorporar Python em uma aplicação. Isso isola Python de um sistema. Por exemplo, variáveis de ambiente são ignoradas, a variável local LC_CTYPE fica inalterada e nenhum manipulador de sinal é registrado.

A função Py_RunMain() pode ser usada para escrever um programa Python personalizado.

Veja também Inicialização, Finalização e Threads.

Ver também

PEP 587 “Configuração da inicialização do Python”.

Exemplo

Exemplo de Python personalizado sendo executado sempre em um modo isolado:

int main(int argc, char **argv)
{
    PyStatus status;

    PyConfig config;
    PyConfig_InitPythonConfig(&config);
    config.isolated = 1;

    /* Decode command line arguments.
       Implicitly preinitialize Python (in isolated mode). */
    status = PyConfig_SetBytesArgv(&config, argc, argv);
    if (PyStatus_Exception(status)) {
        goto exception;
    }

    status = Py_InitializeFromConfig(&config);
    if (PyStatus_Exception(status)) {
        goto exception;
    }
    PyConfig_Clear(&config);

    return Py_RunMain();

exception:
    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);
}

PyWideStringList

type PyWideStringList

Lista de strings wchar_t*.

Se length é diferente de zero, items deve ser diferente de NULL e todas as strings devem ser diferentes de NULL.

Métodos:

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

Anexa item a list.

Python deve ser inicializado previamente antes de chamar essa função.

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

Insere item na list na posição index.

Se index for maior ou igual ao comprimento da list, anexa o item a list.

index deve ser maior que ou igual a 0.

Python deve ser inicializado previamente antes de chamar essa função.

Campos de estrutura:

Py_ssize_t length

Comprimento da lista.

wchar_t **items

Itens da lista.

PyStatus

type PyStatus

Estrutura para armazenar o status de uma função de inicialização: sucesso, erro ou saída.

Para um erro, ela pode armazenar o nome da função C que criou o erro.

Campos de estrutura:

int exitcode

Código de saída. Argumento passado para exit().

const char *err_msg

Mensagem de erro.

const char *func

Nome da função que criou um erro. Pode ser NULL.

Funções para criar um status:

PyStatus PyStatus_Ok(void)

Sucesso.

PyStatus PyStatus_Error(const char *err_msg)

Erro de inicialização com uma mensagem.

err_msg não deve ser NULL.

PyStatus PyStatus_NoMemory(void)

Falha de alocação de memória (sem memória).

PyStatus PyStatus_Exit(int exitcode)

Sai do Python com o código de saída especificado.

Funções para manipular um status:

int PyStatus_Exception(PyStatus status)

O status é um erro ou uma saída? Se verdadeiro, a exceção deve ser tratada; chamando Py_ExitStatusException(), por exemplo.

int PyStatus_IsError(PyStatus status)

O resultado é um erro?

int PyStatus_IsExit(PyStatus status)

O resultado é uma saída?

void Py_ExitStatusException(PyStatus status)

Chama exit(exitcode) se status for uma saída. Exibe a mensagem de erro e sai com um código de saída diferente de zero se status for um erro. Deve ser chamado apenas se PyStatus_Exception(status) for diferente de zero.

Nota

Internamente, Python usa macros que definem PyStatus.func, enquanto funções para criar um status definem func para NULL.

Exemplo:

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

type PyPreConfig

Estrutura usada para pré-inicializar o Python.

A função para inicializar uma pré-configuração:

void PyPreConfig_InitPythonConfig(PyPreConfig *preconfig)

Inicializa a pré-configuração com Configuração do Python.

void PyPreConfig_InitIsolatedConfig(PyPreConfig *preconfig)

Inicializa a pré-configuração com Configuração isolada.

Campos de estrutura:

int allocator

Nome de alocadores de memória em Python:

PYMEM_ALLOCATOR_PYMALLOC and PYMEM_ALLOCATOR_PYMALLOC_DEBUG are not supported if Python is configured using --without-pymalloc.

Veja Gerenciamento de memória.

Padrão: PYMEM_ALLOCATOR_NOT_SET.

int configure_locale

Set the LC_CTYPE locale to the user preferred locale.

If equals to 0, set coerce_c_locale and coerce_c_locale_warn members to 0.

See the locale encoding.

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

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.

See the locale encoding.

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

int coerce_c_locale_warn

Se diferente de zero, emite um aviso se a localidade C for forçada.

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

int dev_mode

Python Development Mode: see PyConfig.dev_mode.

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

int isolated

Isolated mode: see PyConfig.isolated.

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

int legacy_windows_fs_encoding

If non-zero:

Initialized the from PYTHONLEGACYWINDOWSFSENCODING environment variable value.

Disponível apenas no Windows. A macro #ifdef MS_WINDOWS pode ser usada para código específico do Windows.

Padrão: 0.

int parse_argv

Se diferente de zero, Py_PreInitializeFromArgs() e Py_PreInitializeFromBytesArgs() analisam seu argumento argv da mesma forma que o Python regular analisa argumentos de linha de comando: vej Argumentos de linha de comando.

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

int use_environment

Use environment variables? See PyConfig.use_environment.

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

int utf8_mode

If non-zero, enable the Python UTF-8 Mode.

Set to 0 or 1 by the -X utf8 command line option and the PYTHONUTF8 environment variable.

Also set to 1 if the LC_CTYPE locale is C or POSIX.

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

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:

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 speaks UTF-8 */

Py_Initialize();
/* ... use Python API here ... */
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:

void PyConfig_InitPythonConfig(PyConfig *config)

Initialize configuration with the Python Configuration.

void PyConfig_InitIsolatedConfig(PyConfig *config)

Initialize configuration with the Isolated Configuration.

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.

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.

PyStatus PyConfig_SetArgv(PyConfig *config, int argc, wchar_t *const *argv)

Set command line arguments (argv member of config) from the argv list of wide character strings.

Preinitialize Python if needed.

PyStatus PyConfig_SetBytesArgv(PyConfig *config, int argc, char *const *argv)

Set command line arguments (argv member of config) from the argv list of bytes strings. Decode bytes using Py_DecodeLocale().

Preinitialize Python if needed.

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.

PyStatus PyConfig_Read(PyConfig *config)

Read all Python configuration.

Fields which are already initialized are left unchanged.

Fields for path configuration are no longer calculated or modified when calling this function, as of Python 3.11.

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.

Preinitialize Python if needed.

Alterado na versão 3.10: The PyConfig.argv arguments are now only parsed once, PyConfig.parse_argv is set to 2 after arguments are parsed, and arguments are only parsed if PyConfig.parse_argv equals 1.

Alterado na versão 3.11: PyConfig_Read() no longer calculates all paths, and so fields listed under Python Path Configuration may no longer be updated until Py_InitializeFromConfig() is called.

void PyConfig_Clear(PyConfig *config)

Release configuration memory.

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().

Campos de estrutura:

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.

Padrão: NULL.

See also the orig_argv member.

int safe_path

If equals to zero, Py_RunMain() prepends a potentially unsafe path to sys.path at startup:

  • If argv[0] is equal to L"-m" (python -m module), prepend the current working directory.

  • If running a script (python script.py), prepend the script’s directory. If it’s a symbolic link, resolve symbolic links.

  • Otherwise (python -c code and python), prepend an empty string, which means the current working directory.

Set to 1 by the -P command line option and the PYTHONSAFEPATH environment variable.

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

Adicionado na versão 3.11.

wchar_t *base_exec_prefix

sys.base_exec_prefix.

Padrão: 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.

Padrão: NULL.

Part of the Python Path Configuration output.

wchar_t *base_prefix

sys.base_prefix.

Padrão: 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.

Padrão: 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.

Padrão: 0.

int warn_default_encoding

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

Padrão: 0.

Adicionado na versão 3.10.

int code_debug_ranges

If equals to 0, disables the inclusion of the end line and column mappings in code objects. Also disables traceback printing carets to specific error locations.

Set to 0 by the PYTHONNODEBUGRANGES environment variable and by the -X no_debug_ranges command line option.

Padrão: 1.

Adicionado na versão 3.11.

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.

Valores válidos:

  • 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.

Set to 1 by the -X dev option and the PYTHONDEVMODE environment variable.

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

int dump_refs

Dump Python references?

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.

Padrão: 0.

wchar_t *exec_prefix

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

Padrão: NULL.

Part of the Python Path Configuration output.

wchar_t *executable

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

Padrão: 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, 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 startup, 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.

Padrão: 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.

Padrão: 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.

Padrão: 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.

Padrão: 0.

int int_max_str_digits

Configures the integer string conversion length limitation. An initial value of -1 means the value will be taken from the command line or environment or otherwise default to 4300 (sys.int_info.default_max_str_digits). A value of 0 disables the limitation. Values greater than zero but less than 640 (sys.int_info.str_digits_check_threshold) are unsupported and will produce an error.

Configured by the -X int_max_str_digits command line flag or the PYTHONINTMAXSTRDIGITS environment variable.

Default: -1 in Python mode. 4300 (sys.int_info.default_max_str_digits) in isolated mode.

Adicionado na versão 3.12.

int isolated

If greater than 0, enable isolated mode:

  • Set safe_path to 1: don’t prepend a potentially unsafe path to sys.path at Python startup, such as the current directory, the script’s directory or an empty string.

  • Set use_environment to 0: ignore PYTHON environment variables.

  • Set user_site_directory to 0: don’t add the user site directory to sys.path.

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

Set to 1 by the -I command line option.

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

See also the Isolated Configuration and PyPreConfig.isolated.

int legacy_windows_stdio

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

Definida como 1 se a variável de ambiente PYTHONLEGACYWINDOWSSTDIO estiver definida como uma string não vazia.

Disponível apenas no Windows. A macro #ifdef MS_WINDOWS pode ser usada para código específico do Windows.

Padrão: 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.

Padrão: 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", or "DLLs" on Windows).

Part of the Python Path Configuration input.

Adicionado na versão 3.9.

Alterado na versão 3.11: This macro is now used on Windows to locate the standard library extension modules, typically under DLLs. However, for compatibility, note that this value is ignored for any non-standard layouts, including in-tree builds and virtual environments.

wchar_t *pythonpath_env

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

Set by the PYTHONPATH environment variable.

Padrão: 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, Py_InitializeFromConfig() will replace 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.

Padrão: 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.

Padrão: lista vazia.

Adicionado na versão 3.10.

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.

Alterado na versão 3.10: 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.

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

Padrão: 0.

int pathconfig_warnings

If non-zero, calculation of path configuration is allowed to log warnings into stderr. If equals to 0, suppress these warnings.

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

Part of the Python Path Configuration input.

Alterado na versão 3.11: Now also applies on Windows.

wchar_t *prefix

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

Padrão: 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.

Padrão: 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.

Padrão: 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.

Padrão: 0.

wchar_t *run_command

Value of the -c command line option.

Used by Py_RunMain().

Padrão: NULL.

wchar_t *run_filename

Filename passed on the command line: trailing command line argument without -c or -m. It is used by the Py_RunMain() function.

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

See also the PyConfig.skip_source_first_line option.

Padrão: NULL.

wchar_t *run_module

Value of the -m command line option.

Used by Py_RunMain().

Padrão: NULL.

int show_ref_count

Show total reference count at exit (excluding immortal objects)?

Set to 1 by -X showrefcount command line option.

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

Padrão: 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.

Padrão: 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.

Padrão: 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.

Codificação padrão:

Tratador de erros padrão:

  • 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 perf_profiling

Enable compatibility mode with the perf profiler?

If non-zero, initialize the perf trampoline. See Suporte do Python ao perfilador perf do Linux for more information.

Set by -X perf command line option and by the PYTHONPERFSUPPORT environment variable.

Default: -1.

Adicionado na versão 3.12.

int use_environment

Use environment variables?

If equals to zero, ignore the environment variables.

Set to 0 by the -E environment variable.

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 than 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 by the PYTHONVERBOSE environment variable value.

Padrão: 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 (,).

Padrão: lista vazia.

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.

Padrão: 1.

PyWideStringList xoptions

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

Padrão: lista vazia.

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.

Alterado na versão 3.9: 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:

void init_python(void)
{
    PyStatus status;

    PyConfig config;
    PyConfig_InitPythonConfig(&config);

    /* Set the program name. Implicitly preinitialize Python. */
    status = PyConfig_SetString(&config, &config.program_name,
                                L"/path/to/my_program");
    if (PyStatus_Exception(status)) {
        goto exception;
    }

    status = Py_InitializeFromConfig(&config);
    if (PyStatus_Exception(status)) {
        goto exception;
    }
    PyConfig_Clear(&config);
    return;

exception:
    PyConfig_Clear(&config);
    Py_ExitStatusException(status);
}

More complete example modifying the default configuration, read the configuration, and then override some parameters. Note that since 3.11, many parameters are not calculated until initialization, and so values cannot be read from the configuration structure. Any values set before initialize is called will be left unchanged by initialization:

PyStatus init_python(const char *program_name)
{
    PyStatus status;

    PyConfig config;
    PyConfig_InitPythonConfig(&config);

    /* Set the program name before reading the configuration
       (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;
    }

    /* Specify sys.path explicitly */
    /* If you want to modify the default set of paths, finish
       initialization first and then use PySys_GetObject("path") */
    config.module_search_paths_set = 1;
    status = PyWideStringList_Append(&config.module_search_paths,
                                     L"/path/to/stdlib");
    if (PyStatus_Exception(status)) {
        goto done;
    }
    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;
}

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, environment 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 to determine paths that are unspecified. Ensure PyConfig.home is specified to avoid computing the default path configuration.

Configuração do Python

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, module_search_paths will be used without modification.

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

  • ._pth file (ex: python._pth)

  • pybuilddir.txt (Unix only)

If a ._pth file is present:

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 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:

Private provisional API:

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 calculate 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:

void init_python(void)
{
    PyStatus status;

    PyConfig config;
    PyConfig_InitPythonConfig(&config);
    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);
    }
}