New in version 3.8.
Structures:
Functions:
The preconfiguration (PyPreConfig
type) is stored in _PyRuntime.preconfig
and the configuration (PyConfig
type) is stored in PyInterpreterState.config
.
See also Initialization, Finalization, and Threads.
PyWideStringList
List of wchar_t*
strings.
If length is non-zero, items must be non-NULL
and all strings must be non-NULL
.
Methods:
PyWideStringList_Append
Append item to list.
Python must be preinitialized to call this function.
PyWideStringList_Insert
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:
length
List length.
items
List items.
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:
exitcode
Exit code. Argument passed to exit()
.
err_msg
Error message.
func
Name of the function which created an error, can be NULL
.
Functions to create a status:
Functions to handle a status:
PyStatus_Exception
Is the status an error or an exit? If true, the exception must be handled; by calling Py_ExitStatusException()
for example.
Py_ExitStatusException
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
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:
PyPreConfig_InitIsolatedConfig
Initialize the preconfiguration with Python Configuration.
PyPreConfig_InitPythonConfig
Initialize the preconfiguration with Isolated Configuration.
Structure fields:
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
): Python pymalloc memory allocator
PYMEM_ALLOCATOR_PYMALLOC_DEBUG
(6
): Python pymalloc memory allocator with debug hooks
PYMEM_ALLOCATOR_PYMALLOC
and PYMEM_ALLOCATOR_PYMALLOC_DEBUG
are not supported if Python is configured using --without-pymalloc
See Memory Management.
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
to 0.
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.
coerce_c_locale_warn
If non-zero, emit a warning if the C locale is coerced.
dev_mode
See PyConfig.dev_mode
.
isolated
See PyConfig.isolated
.
legacy_windows_fs_encoding
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.
parse_argv
If non-zero, Py_PreInitializeFromArgs()
and Py_PreInitializeFromBytesArgs()
parse their argv
argument the same way the regular Python parses command line arguments: see Command Line Arguments.
use_environment
utf8_mode
If non-zero, enable the UTF-8 mode.
Functions to preinitialize Python:
Py_PreInitialize
Preinitialize Python from preconfig preconfiguration.
Py_PreInitializeFromBytesArgs
Preinitialize Python from preconfig preconfiguration and command line arguments (bytes strings).
Py_PreInitializeFromArgs
Preinitialize Python from preconfig preconfiguration and command line arguments (wide strings).
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 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 Python preinitialization, whereas calling directly malloc()
and free()
is always safe. 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
Structure containing most parameters to configure Python.
Structure methods:
PyConfig_InitPythonConfig
Initialize configuration with Python Configuration.
PyConfig_InitIsolatedConfig
Initialize configuration with Isolated Configuration.
PyConfig_SetString
Copy the wide character string str into *config_str
.
Preinitialize Python if needed.
PyConfig_SetBytesString
Decode str using Py_DecodeLocale()
and set the result into *config_str
.
Preinitialize Python if needed.
PyConfig_SetArgv
Set command line arguments from wide character strings.
Preinitialize Python if needed.
PyConfig_SetBytesArgv
Set command line arguments: decode bytes using Py_DecodeLocale()
.
Preinitialize Python if needed.
PyConfig_SetWideStringList
Set the list of wide strings list to length and items.
Preinitialize Python if needed.
PyConfig_Read
Read all Python configuration.
Fields which are already initialized are left unchanged.
Preinitialize Python if needed.
Most PyConfig
methods preinitialize Python if needed. In that case, the Python preinitialization configuration 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 first, 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:
argv
Command line arguments, sys.argv
. See parse_argv
to parse argv
the same way the regular Python parses Python command line arguments. If argv
is empty, an empty string is added to ensure that sys.argv
always exists and is never empty.
base_exec_prefix
base_executable
sys._base_executable
: __PYVENV_LAUNCHER__
environment variable value, or copy of PyConfig.executable
.
base_prefix
buffered_stdio
If equals to 0, enable unbuffered mode, making the stdout and stderr streams unbuffered.
stdin is always opened in buffered mode.
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.
check_hash_pycs_mode
Control the validation behavior of hash-based .pyc
files (see PEP 552): --check-hash-based-pycs
command line option value.
Valid values: always
, never
and default
.
The default value is: default
.
configure_c_stdio
If non-zero, configure C standard streams (stdio
, stdout
, stdout
). For example, set their mode to O_BINARY
on Windows.
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).
exec_prefix
executable
faulthandler
If non-zero, call faulthandler.enable()
at startup.
filesystem_encoding
Filesystem encoding, sys.getfilesystemencoding()
.
filesystem_errors
Filesystem encoding errors, sys.getfilesystemencodeerrors()
.
hash_seed
use_hash_seed
Randomized hash function seed.
If use_hash_seed
is zero, a seed is chosen randomly at Pythonstartup, and hash_seed
is ignored.
home
Python home directory.
Initialized from PYTHONHOME
environment variable value by default.
import_time
If non-zero, profile import time.
inspect
Enter interactive mode after executing a script or a command.
install_signal_handlers
Install signal handlers?
interactive
Interactive mode.
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.
legacy_windows_stdio
If non-zero, use io.FileIO
instead of io.WindowsConsoleIO
for sys.stdin
, sys.stdout
and sys.stderr
.
Only available on Windows. #ifdef MS_WINDOWS
macro can be used for Windows specific code.
malloc_stats
If non-zero, dump statistics on Python pymalloc memory allocator at exit.
The option is ignored if Python is built using --without-pymalloc
.
pythonpath_env
Module search paths as a string separated by DELIM
(os.path.pathsep
).
Initialized from PYTHONPATH
environment variable value by default.
module_search_paths
module_search_paths_set
sys.path
. If module_search_paths_set
is equal to 0, the module_search_paths
is overridden by the function calculating the Path Configuration.
optimization_level
Compilation optimization level:
0: Peephole optimizer (and __debug__
is set to True
)
1: Remove assertions, set __debug__
to False
2: Strip docstrings
parse_argv
If non-zero, parse argv
the same way the regular Python command line arguments, and strip Python arguments from argv
: see Command Line Arguments.
parser_debug
If non-zero, turn on parser debugging output (for expert only, depending on compilation options).
pathconfig_warnings
If equal to 0, suppress warnings when calculating the Path Configuration (Unix only, Windows does not log any warning). Otherwise, warnings are written into stderr
.
prefix
program_name
Program name. Used to initialize executable
, and in early error messages.
pycache_prefix
sys.pycache_prefix
: .pyc
cache prefix.
If NULL
, sys.pycache_prefix
is set to None
.
quiet
Quiet mode. For example, don?t display the copyright and version messages in interactive mode.
run_command
python3 -c COMMAND
argument. Used by Py_RunMain()
.
run_filename
python3 FILENAME
argument. Used by Py_RunMain()
.
run_module
python3 -m MODULE
argument. Used by Py_RunMain()
.
show_alloc_count
Show allocation counts at exit?
Set to 1 by -X showalloccount
command line option.
Need a special Python build with COUNT_ALLOCS
macro defined.
show_ref_count
Show total reference count at exit?
Set to 1 by -X showrefcount
command line option.
Need a debug build of Python (Py_REF_DEBUG
macro must be defined).
skip_source_first_line
Skip the first line of the source?
stdio_encoding
stdio_errors
Encoding and encoding errors of sys.stdin
, sys.stdout
and sys.stderr
.
tracemalloc
If non-zero, call tracemalloc.start()
at startup.
use_environment
If greater than 0, use environment variables.
verbose
If non-zero, enable verbose mode.
warnoptions
sys.warnoptions
: options of the warnings
module to build warnings filters: lowest to highest priority.
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).
write_bytecode
If non-zero, write .pyc
files.
sys.dont_write_bytecode
is initialized to the inverted value of write_bytecode
.
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 Command Line Arguments.
The xoptions
options are parsed to set other options: see -X
option.
Function to initialize Python:
Py_InitializeFromConfig
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.
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 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;
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;
}
/* 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;
}
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 Path Configuration (?output fields?) to ignore these configuration files and avoid the function computing the default path 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 UTF-8 Mode (PEP 540) depending on the LC_CTYPE locale, PYTHONUTF8
and PYTHONCOERCECLOCALE
environment variables.
Example of customized Python always running in isolated mode:
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 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);
}
PyConfig
contains multiple fields for the path configuration:
Path configuration inputs:
current working directory: to get absolute paths
PATH
environment variable to get the program full path (from PyConfig.program_name
)
__PYVENV_LAUNCHER__
environment variable
(Windows only) Application paths in the registry under ?SoftwarePythonPythonCoreX.YPythonPath? of HKEY_CURRENT_USER and HKEY_LOCAL_MACHINE (where X.Y is the Python version).
Path configuration output fields:
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 run_filename
is set and is a directory which contains a __main__.py
script, prepend run_filename
to sys.path
.
If isolated
is zero:
If run_module
is set, prepend the current directory to sys.path
. Do nothing if the current directory cannot be read.
If run_filename
is set, prepend the directory of the filename to sys.path
.
Otherwise, prepend an empty string to 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
(Windows only)
pybuilddir.txt
(Unix only)
The __PYVENV_LAUNCHER__
environment variable is used to set PyConfig.base_executable
Py_RunMain
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()
.
This section is a private provisional API introducing multi-phase initialization, the core feature of the PEP 432:
?Core? initialization phase, ?bare minimum Python?:
?Main? initialization phase, Python is fully initialized:
Install and configure importlib
;
Apply the Path Configuration;
Install signal handlers;
Finish sys
module initialization (ex: create sys.stdout
and sys.path
);
Enable optional features like faulthandler
and tracemalloc
;
Import the site
module;
etc.
Private provisional API:
PyConfig._init_main
: if set to 0, Py_InitializeFromConfig()
stops at the ?Core? initialization phase.
_Py_InitializeMain
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:
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);
}
}
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
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:
PyPreConfig_InitIsolatedConfig
Initialize the preconfiguration with Python Configuration.
PyPreConfig_InitPythonConfig
Initialize the preconfiguration with Isolated Configuration.
Structure fields:
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
): Python pymalloc memory allocator
PYMEM_ALLOCATOR_PYMALLOC_DEBUG
(6
): Python pymalloc memory allocator with debug hooks
PYMEM_ALLOCATOR_PYMALLOC
and PYMEM_ALLOCATOR_PYMALLOC_DEBUG
are not supported if Python is configured using --without-pymalloc
See Memory Management.
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
to 0.
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.
coerce_c_locale_warn
If non-zero, emit a warning if the C locale is coerced.
dev_mode
See PyConfig.dev_mode
.
isolated
See PyConfig.isolated
.
legacy_windows_fs_encoding
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.
parse_argv
If non-zero, Py_PreInitializeFromArgs()
and Py_PreInitializeFromBytesArgs()
parse their argv
argument the same way the regular Python parses command line arguments: see Command Line Arguments.
use_environment
utf8_mode
If non-zero, enable the UTF-8 mode.
Functions to preinitialize Python:
Py_PreInitialize
Preinitialize Python from preconfig preconfiguration.
Py_PreInitializeFromBytesArgs
Preinitialize Python from preconfig preconfiguration and command line arguments (bytes strings).
Py_PreInitializeFromArgs
Preinitialize Python from preconfig preconfiguration and command line arguments (wide strings).
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 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 Python preinitialization, whereas calling directly malloc()
and free()
is always safe. 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
Structure containing most parameters to configure Python.
Structure methods:
PyConfig_InitPythonConfig
Initialize configuration with Python Configuration.
PyConfig_InitIsolatedConfig
Initialize configuration with Isolated Configuration.
PyConfig_SetString
Copy the wide character string str into *config_str
.
Preinitialize Python if needed.
PyConfig_SetBytesString
Decode str using Py_DecodeLocale()
and set the result into *config_str
.
Preinitialize Python if needed.
PyConfig_SetArgv
Set command line arguments from wide character strings.
Preinitialize Python if needed.
PyConfig_SetBytesArgv
Set command line arguments: decode bytes using Py_DecodeLocale()
.
Preinitialize Python if needed.
PyConfig_SetWideStringList
Set the list of wide strings list to length and items.
Preinitialize Python if needed.
PyConfig_Read
Read all Python configuration.
Fields which are already initialized are left unchanged.
Preinitialize Python if needed.
Most PyConfig
methods preinitialize Python if needed. In that case, the Python preinitialization configuration 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 first, 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:
argv
Command line arguments, sys.argv
. See parse_argv
to parse argv
the same way the regular Python parses Python command line arguments. If argv
is empty, an empty string is added to ensure that sys.argv
always exists and is never empty.
base_exec_prefix
base_executable
sys._base_executable
: __PYVENV_LAUNCHER__
environment variable value, or copy of PyConfig.executable
.
base_prefix
buffered_stdio
If equals to 0, enable unbuffered mode, making the stdout and stderr streams unbuffered.
stdin is always opened in buffered mode.
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.
check_hash_pycs_mode
Control the validation behavior of hash-based .pyc
files (see PEP 552): --check-hash-based-pycs
command line option value.
Valid values: always
, never
and default
.
The default value is: default
.
configure_c_stdio
If non-zero, configure C standard streams (stdio
, stdout
, stdout
). For example, set their mode to O_BINARY
on Windows.
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).
exec_prefix
executable
faulthandler
If non-zero, call faulthandler.enable()
at startup.
filesystem_encoding
Filesystem encoding, sys.getfilesystemencoding()
.
filesystem_errors
Filesystem encoding errors, sys.getfilesystemencodeerrors()
.
hash_seed
use_hash_seed
Randomized hash function seed.
If use_hash_seed
is zero, a seed is chosen randomly at Pythonstartup, and hash_seed
is ignored.
home
Python home directory.
Initialized from PYTHONHOME
environment variable value by default.
import_time
If non-zero, profile import time.
inspect
Enter interactive mode after executing a script or a command.
install_signal_handlers
Install signal handlers?
interactive
Interactive mode.
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.
legacy_windows_stdio
If non-zero, use io.FileIO
instead of io.WindowsConsoleIO
for sys.stdin
, sys.stdout
and sys.stderr
.
Only available on Windows. #ifdef MS_WINDOWS
macro can be used for Windows specific code.
malloc_stats
If non-zero, dump statistics on Python pymalloc memory allocator at exit.
The option is ignored if Python is built using --without-pymalloc
.
pythonpath_env
Module search paths as a string separated by DELIM
(os.path.pathsep
).
Initialized from PYTHONPATH
environment variable value by default.
module_search_paths
module_search_paths_set
sys.path
. If module_search_paths_set
is equal to 0, the module_search_paths
is overridden by the function calculating the Path Configuration.
optimization_level
Compilation optimization level:
0: Peephole optimizer (and __debug__
is set to True
)
1: Remove assertions, set __debug__
to False
2: Strip docstrings
parse_argv
If non-zero, parse argv
the same way the regular Python command line arguments, and strip Python arguments from argv
: see Command Line Arguments.
parser_debug
If non-zero, turn on parser debugging output (for expert only, depending on compilation options).
pathconfig_warnings
If equal to 0, suppress warnings when calculating the Path Configuration (Unix only, Windows does not log any warning). Otherwise, warnings are written into stderr
.
prefix
program_name
Program name. Used to initialize executable
, and in early error messages.
pycache_prefix
sys.pycache_prefix
: .pyc
cache prefix.
If NULL
, sys.pycache_prefix
is set to None
.
quiet
Quiet mode. For example, don?t display the copyright and version messages in interactive mode.
run_command
python3 -c COMMAND
argument. Used by Py_RunMain()
.
run_filename
python3 FILENAME
argument. Used by Py_RunMain()
.
run_module
python3 -m MODULE
argument. Used by Py_RunMain()
.
show_alloc_count
Show allocation counts at exit?
Set to 1 by -X showalloccount
command line option.
Need a special Python build with COUNT_ALLOCS
macro defined.
show_ref_count
Show total reference count at exit?
Set to 1 by -X showrefcount
command line option.
Need a debug build of Python (Py_REF_DEBUG
macro must be defined).
skip_source_first_line
Skip the first line of the source?
stdio_encoding
stdio_errors
Encoding and encoding errors of sys.stdin
, sys.stdout
and sys.stderr
.
tracemalloc
If non-zero, call tracemalloc.start()
at startup.
use_environment
If greater than 0, use environment variables.
verbose
If non-zero, enable verbose mode.
warnoptions
sys.warnoptions
: options of the warnings
module to build warnings filters: lowest to highest priority.
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).
write_bytecode
If non-zero, write .pyc
files.
sys.dont_write_bytecode
is initialized to the inverted value of write_bytecode
.
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 Command Line Arguments.
The xoptions
options are parsed to set other options: see -X
option.
Function to initialize Python:
Py_InitializeFromConfig
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.
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 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;
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;
}
/* 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;
}
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 Path Configuration (?output fields?) to ignore these configuration files and avoid the function computing the default path 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 UTF-8 Mode (PEP 540) depending on the LC_CTYPE locale, PYTHONUTF8
and PYTHONCOERCECLOCALE
environment variables.
Example of customized Python always running in isolated mode:
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 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);
}
PyConfig
contains multiple fields for the path configuration:
Path configuration inputs:
current working directory: to get absolute paths
PATH
environment variable to get the program full path (from PyConfig.program_name
)
__PYVENV_LAUNCHER__
environment variable
(Windows only) Application paths in the registry under ?SoftwarePythonPythonCoreX.YPythonPath? of HKEY_CURRENT_USER and HKEY_LOCAL_MACHINE (where X.Y is the Python version).
Path configuration output fields:
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 run_filename
is set and is a directory which contains a __main__.py
script, prepend run_filename
to sys.path
.
If isolated
is zero:
If run_module
is set, prepend the current directory to sys.path
. Do nothing if the current directory cannot be read.
If run_filename
is set, prepend the directory of the filename to sys.path
.
Otherwise, prepend an empty string to 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
(Windows only)
pybuilddir.txt
(Unix only)
The __PYVENV_LAUNCHER__
environment variable is used to set PyConfig.base_executable
Py_RunMain
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()
.
This section is a private provisional API introducing multi-phase initialization, the core feature of the PEP 432:
?Core? initialization phase, ?bare minimum Python?:
?Main? initialization phase, Python is fully initialized:
Install and configure importlib
;
Apply the Path Configuration;
Install signal handlers;
Finish sys
module initialization (ex: create sys.stdout
and sys.path
);
Enable optional features like faulthandler
and tracemalloc
;
Import the site
module;
etc.
Private provisional API:
PyConfig._init_main
: if set to 0, Py_InitializeFromConfig()
stops at the ?Core? initialization phase.
_Py_InitializeMain
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:
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);
}
}