python_doc_md/Beginner/using/cmdline.md

Command line and environment {#using-on-general}

The CPython interpreter scans the command line and the environment for various settings.

::: impl-detail Other implementations' command line schemes may differ. See implementations{.interpreted-text role="ref"} for further resources. :::

Command line {#using-on-cmdline}

When invoking Python, you may specify any of these options:

python [-bBdEhiIOPqRsSuvVWx?] [-c command | -m module-name | script | - ] [args]

The most common use case is, of course, a simple invocation of a script:

python myscript.py

Interface options {#using-on-interface-options}

The interpreter interface resembles that of the UNIX shell, but provides some additional methods of invocation:

• When called with standard input connected to a tty device, it prompts for commands and executes them until an EOF (an end-of-file character, you can produce that with Ctrl-D{.interpreted-text role="kbd"} on UNIX or Ctrl-Z, Enter{.interpreted-text role="kbd"} on Windows) is read. For more on interactive mode, see tut-interac{.interpreted-text role="ref"}.
• When called with a file name argument or with a file as standard input, it reads and executes a script from that file.
• When called with a directory name argument, it reads and executes an appropriately named script from that directory.
• When called with -c command, it executes the Python statement(s) given as command. Here command may contain multiple statements separated by newlines. Leading whitespace is significant in Python statements!
• When called with -m module-name, the given module is located on the Python module path and executed as a script.

In non-interactive mode, the entire input is parsed before it is executed.

An interface option terminates the list of options consumed by the interpreter, all consecutive arguments will end up in sys.argv{.interpreted-text role="data"} -- note that the first element, subscript zero (sys.argv[0]), is a string reflecting the program's source.

::::: option

-c <command>

:

Execute the Python code in command. command can be one or more statements separated by newlines, with significant leading whitespace as in normal module code.

If this option is given, the first element of sys.argv{.interpreted-text role="data"} will be "-c" and the current directory will be added to the start of sys.path{.interpreted-text role="data"} (allowing modules in that directory to be imported as top level modules).

::: audit-event cpython.run_command command cmdoption-c :::

::: versionchanged 3.14 command is automatically dedented before execution. ::: :::::

::::::::: option

-m <module-name>

:

Search sys.path{.interpreted-text role="data"} for the named module and execute its contents as the __main__{.interpreted-text role="mod"} module.

Since the argument is a module name, you must not give a file extension (.py). The module name should be a valid absolute Python module name, but the implementation may not always enforce this (e.g. it may allow you to use a name that includes a hyphen).

Package names (including namespace packages) are also permitted. When a package name is supplied instead of a normal module, the interpreter will execute <pkg>.__main__ as the main module. This behaviour is deliberately similar to the handling of directories and zipfiles that are passed to the interpreter as the script argument.

:::: note ::: title Note :::

This option cannot be used with built-in modules and extension modules written in C, since they do not have Python module files. However, it can still be used for precompiled modules, even if the original source file is not available. ::::

If this option is given, the first element of sys.argv{.interpreted-text role="data"} will be the full path to the module file (while the module file is being located, the first element will be set to "-m"). As with the -c{.interpreted-text role="option"} option, the current directory will be added to the start of sys.path{.interpreted-text role="data"}.

-I{.interpreted-text role="option"} option can be used to run the script in isolated mode where sys.path{.interpreted-text role="data"} contains neither the current directory nor the user's site-packages directory. All PYTHON* environment variables are ignored, too.

Many standard library modules contain code that is invoked on their execution as a script. An example is the timeit{.interpreted-text role="mod"} module:

python -m timeit -s "setup here" "benchmarked code here"
python -m timeit -h # for details

::: audit-event cpython.run_module module-name cmdoption-m :::

::: seealso runpy.run_module{.interpreted-text role="func"} Equivalent functionality directly available to Python code

338{.interpreted-text role="pep"} -- Executing modules as scripts :::

::: versionchanged 3.1 Supply the package name to run a __main__ submodule. :::

::: versionchanged 3.4 namespace packages are also supported ::: :::::::::

::::: {#cmdarg-dash} :::: describe

Read commands from standard input (sys.stdin{.interpreted-text role="data"}). If standard input is a terminal, -i{.interpreted-text role="option"} is implied.

If this option is given, the first element of sys.argv{.interpreted-text role="data"} will be "-" and the current directory will be added to the start of sys.path{.interpreted-text role="data"}.

::: audit-event cpython.run_stdin "" "" ::: :::: :::::

:::::: {#cmdarg-script} ::::: describe <script>

Execute the Python code contained in script, which must be a filesystem path (absolute or relative) referring to either a Python file, a directory containing a __main__.py file, or a zipfile containing a __main__.py file.

If this option is given, the first element of sys.argv{.interpreted-text role="data"} will be the script name as given on the command line.

If the script name refers directly to a Python file, the directory containing that file is added to the start of sys.path{.interpreted-text role="data"}, and the file is executed as the __main__{.interpreted-text role="mod"} module.

If the script name refers to a directory or zipfile, the script name is added to the start of sys.path{.interpreted-text role="data"} and the __main__.py file in that location is executed as the __main__{.interpreted-text role="mod"} module.

-I{.interpreted-text role="option"} option can be used to run the script in isolated mode where sys.path{.interpreted-text role="data"} contains neither the script's directory nor the user's site-packages directory. All PYTHON* environment variables are ignored, too.

::: audit-event cpython.run_file filename :::

::: seealso runpy.run_path{.interpreted-text role="func"} Equivalent functionality directly available to Python code ::: ::::: ::::::

If no interface option is given, -i{.interpreted-text role="option"} is implied, sys.argv[0] is an empty string ("") and the current directory will be added to the start of sys.path{.interpreted-text role="data"}. Also, tab-completion and history editing is automatically enabled, if available on your platform (see rlcompleter-config{.interpreted-text role="ref"}).

::: seealso tut-invoking{.interpreted-text role="ref"} :::

::: versionchanged 3.4 Automatic enabling of tab-completion and history editing. :::

Generic options {#using-on-generic-options}

::: option -? -h --help

Print a short description of all command line options and corresponding environment variables and exit. :::

:::: option

--help-env

:

Print a short description of Python-specific environment variables and exit.

::: versionadded 3.11 ::: ::::

:::: option

--help-xoptions

:

Print a description of implementation-specific -X{.interpreted-text role="option"} options and exit.

::: versionadded 3.11 ::: ::::

:::: option

--help-all

:

Print complete usage information and exit.

::: versionadded 3.11 ::: ::::

:::: option

-V

:

--version

:

Print the Python version number and exit. Example output could be:

Python 3.8.0b2+

When given twice, print more information about the build, like:

Python 3.8.0b2+ (3.8:0c076caaa8, Apr 20 2019, 21:55:00)
[GCC 6.2.0 20161005]

::: versionadded 3.6 The -VV option. ::: ::::

Miscellaneous options {#using-on-misc-options}

::::: option

-b

:

Issue a warning when converting bytes{.interpreted-text role="class"} or bytearray{.interpreted-text role="class"} to str{.interpreted-text role="class"} without specifying encoding or comparing !bytes{.interpreted-text role="class"} or !bytearray{.interpreted-text role="class"} with !str{.interpreted-text role="class"} or !bytes{.interpreted-text role="class"} with int{.interpreted-text role="class"}. Issue an error when the option is given twice (!-bb{.interpreted-text role="option"}).

::: versionchanged 3.5 Affects also comparisons of bytes{.interpreted-text role="class"} with int{.interpreted-text role="class"}. :::

::: deprecated 3.15

Deprecate -b{.interpreted-text role="option"} and !-bb{.interpreted-text role="option"} command line options and schedule them to become no-op in Python 3.17. These were primarily helpers for the Python 2 -> 3 transition. Starting with Python 3.17, no BytesWarning{.interpreted-text role="exc"} will be raised for these cases; use a type checker instead. ::: :::::

::: option

-B

:

If given, Python won't try to write .pyc files on the import of source modules. See also PYTHONDONTWRITEBYTECODE{.interpreted-text role="envvar"}. :::

::: option --check-hash-based-pycs default|always|never

Control the validation behavior of hash-based .pyc files. See pyc-invalidation{.interpreted-text role="ref"}. When set to default, checked and unchecked hash-based bytecode cache files are validated according to their default semantics. When set to always, all hash-based .pyc files, whether checked or unchecked, are validated against their corresponding source file. When set to never, hash-based .pyc files are not validated against their corresponding source files.

The semantics of timestamp-based .pyc files are unaffected by this option. :::

::: option

-d

:

Turn on parser debugging output (for expert only). See also the PYTHONDEBUG{.interpreted-text role="envvar"} environment variable.

This option requires a debug build of Python <debug-build>{.interpreted-text role="ref"}, otherwise it's ignored. :::

::: option

-E

:

Ignore all PYTHON* environment variables, e.g. PYTHONPATH{.interpreted-text role="envvar"} and PYTHONHOME{.interpreted-text role="envvar"}, that might be set.

See also the -P{.interpreted-text role="option"} and -I{.interpreted-text role="option"} (isolated) options. :::

::: option

-i

:

Enter interactive mode after execution.

Using the -i{.interpreted-text role="option"} option will enter interactive mode in any of the following circumstances:

• When a script is passed as first argument
• When the -c{.interpreted-text role="option"} option is used
• When the -m{.interpreted-text role="option"} option is used

Interactive mode will start even when sys.stdin{.interpreted-text role="data"} does not appear to be a terminal. The PYTHONSTARTUP{.interpreted-text role="envvar"} file is not read.

This can be useful to inspect global variables or a stack trace when a script raises an exception. See also PYTHONINSPECT{.interpreted-text role="envvar"}. :::

:::: option

-I

:

Run Python in isolated mode. This also implies -E{.interpreted-text role="option"}, -P{.interpreted-text role="option"} and -s{.interpreted-text role="option"} options.

In isolated mode sys.path{.interpreted-text role="data"} contains neither the script's directory nor the user's site-packages directory. All PYTHON* environment variables are ignored, too. Further restrictions may be imposed to prevent the user from injecting malicious code.

::: versionadded 3.4 ::: ::::

:::: option

-O

:

Remove assert statements and any code conditional on the value of __debug__{.interpreted-text role="const"}. Augment the filename for compiled (bytecode{.interpreted-text role="term"}) files by adding .opt-1 before the .pyc extension (see 488{.interpreted-text role="pep"}). See also PYTHONOPTIMIZE{.interpreted-text role="envvar"}.

::: versionchanged 3.5 Modify .pyc filenames according to 488{.interpreted-text role="pep"}. ::: ::::

:::: option

-OO

:

Do -O{.interpreted-text role="option"} and also discard docstrings. Augment the filename for compiled (bytecode{.interpreted-text role="term"}) files by adding .opt-2 before the .pyc extension (see 488{.interpreted-text role="pep"}).

::: versionchanged 3.5 Modify .pyc filenames according to 488{.interpreted-text role="pep"}. ::: ::::

:::: option

-P

:

Don't prepend a potentially unsafe path to sys.path{.interpreted-text role="data"}:

• python -m module command line: Don't prepend the current working directory.
• python script.py command line: Don't prepend the script's directory. If it's a symbolic link, resolve symbolic links.
• python -c code and python (REPL) command lines: Don't prepend an empty string, which means the current working directory.

See also the PYTHONSAFEPATH{.interpreted-text role="envvar"} environment variable, and -E{.interpreted-text role="option"} and -I{.interpreted-text role="option"} (isolated) options.

::: versionadded 3.11 ::: ::::

:::: option

-q

:

Don't display the copyright and version messages even in interactive mode.

::: versionadded 3.2 ::: ::::

::::: option

-R

:

Turn on hash randomization. This option only has an effect if the PYTHONHASHSEED{.interpreted-text role="envvar"} environment variable is set to anything other than random, since hash randomization is enabled by default.

On previous versions of Python, this option turns on hash randomization, so that the ~object.__hash__{.interpreted-text role="meth"} values of str and bytes objects are "salted" with an unpredictable random value. Although they remain constant within an individual Python process, they are not predictable between repeated invocations of Python.

Hash randomization is intended to provide protection against a denial-of-service caused by carefully chosen inputs that exploit the worst case performance of a dict construction, O(n^2^) complexity. See http://ocert.org/advisories/ocert-2011-003.html for details.

PYTHONHASHSEED{.interpreted-text role="envvar"} allows you to set a fixed value for the hash seed secret.

::: versionadded 3.2.3 :::

::: versionchanged 3.7 The option is no longer ignored. ::: :::::

:::: option

-s

:

Don't add the user site-packages directory <site.USER_SITE>{.interpreted-text role="data"} to sys.path{.interpreted-text role="data"}.

See also PYTHONNOUSERSITE{.interpreted-text role="envvar"}.

::: seealso 370{.interpreted-text role="pep"} -- Per user site-packages directory ::: ::::

::: option

-S

:

Disable the import of the module site{.interpreted-text role="mod"} and the site-dependent manipulations of sys.path{.interpreted-text role="data"} that it entails. Also disable these manipulations if site{.interpreted-text role="mod"} is explicitly imported later (call site.main{.interpreted-text role="func"} if you want them to be triggered). :::

:::: option

-u

:

Force the stdout and stderr streams to be unbuffered. This option has no effect on the stdin stream.

See also PYTHONUNBUFFERED{.interpreted-text role="envvar"}.

::: versionchanged 3.7 The text layer of the stdout and stderr streams now is unbuffered. ::: ::::

:::: option

-v

:

Print a message each time a module is initialized, showing the place (filename or built-in module) from which it is loaded. When given twice (!-vv{.interpreted-text role="option"}), print a message for each file that is checked for when searching for a module. Also provides information on module cleanup at exit.

::: versionchanged 3.10 The site{.interpreted-text role="mod"} module reports the site-specific paths and .pth{.interpreted-text role="file"} files being processed. :::

See also PYTHONVERBOSE{.interpreted-text role="envvar"}. ::::

Warning control. Python's warning machinery by default prints warning messages to sys.stderr{.interpreted-text role="data"}.

The simplest settings apply a particular action unconditionally to all warnings emitted by a process (even those that are otherwise ignored by default):

-Wdefault  # Warn once per call location
-Werror    # Convert to exceptions
-Walways   # Warn every time
-Wall      # Same as -Walways
-Wmodule   # Warn once per calling module
-Wonce     # Warn once per Python process
-Wignore   # Never warn

The action names can be abbreviated as desired and the interpreter will resolve them to the appropriate action name. For example, -Wi is the same as -Wignore.

The full form of argument is:

action:message:category:module:lineno

Empty fields match all values; trailing empty fields may be omitted. For example -W ignore::DeprecationWarning ignores all DeprecationWarning warnings.

The action field is as explained above but only applies to warnings that match the remaining fields.

The message field must match the start of the warning message; this match is case-insensitive. If it starts and ends with a forward slash (/), it specifies a regular expression, otherwise it specifies a literal string.

The category field matches the warning category (ex: DeprecationWarning). This must be a class name; the match test whether the actual warning category of the message is a subclass of the specified warning category.

The module field matches the (fully qualified) module name; this match is case-sensitive. If it starts and ends with a forward slash (/), it specifies a regular expression that the start of the fully qualified module name must match, otherwise it specifies a literal string that the fully qualified module name must be equal to.

The lineno field matches the line number, where zero matches all line numbers and is thus equivalent to an omitted line number.

Multiple -W{.interpreted-text role="option"} options can be given; when a warning matches more than one option, the action for the last matching option is performed. Invalid -W{.interpreted-text role="option"} options are ignored (though, a warning message is printed about invalid options when the first warning is issued).

Warnings can also be controlled using the PYTHONWARNINGS{.interpreted-text role="envvar"} environment variable and from within a Python program using the warnings{.interpreted-text role="mod"} module. For example, the warnings.filterwarnings{.interpreted-text role="func"} function can be used to use a regular expression on the warning message.

See warning-filter{.interpreted-text role="ref"} and describing-warning-filters{.interpreted-text role="ref"} for more details.

::: versionchanged 3.15 Added regular expression support for message and module. :::

::: option

-x

:

Skip the first line of the source, allowing use of non-Unix forms of #!cmd. This is intended for a DOS specific hack only. :::

:::::: option

-X

:

Reserved for various implementation-specific options. CPython currently defines the following possible values:

• -X faulthandler to enable faulthandler{.interpreted-text role="mod"}. See also PYTHONFAULTHANDLER{.interpreted-text role="envvar"}.

  ::: versionadded 3.3 :::

• -X showrefcount to output the total reference count and number of used memory blocks when the program finishes or after each statement in the interactive interpreter. This only works on debug builds <debug-build>{.interpreted-text role="ref"}.

  ::: versionadded 3.4 :::

• -X tracemalloc to start tracing Python memory allocations using the tracemalloc{.interpreted-text role="mod"} module. By default, only the most recent frame is stored in a traceback of a trace. Use -X tracemalloc=NFRAME to start tracing with a traceback limit of NFRAME frames. See tracemalloc.start{.interpreted-text role="func"} and PYTHONTRACEMALLOC{.interpreted-text role="envvar"} for more information.

  ::: versionadded 3.4 :::

• -X int_max_str_digits configures the integer string conversion length limitation <int_max_str_digits>{.interpreted-text role="ref"}. See also PYTHONINTMAXSTRDIGITS{.interpreted-text role="envvar"}.

  ::: versionadded 3.11 :::

• -X importtime to show how long each import takes. It shows module name, cumulative time (including nested imports) and self time (excluding nested imports). Note that its output may be broken in multi-threaded application. Typical usage is python -X importtime -c 'import asyncio'.

  -X importtime=2 enables additional output that indicates when an imported module has already been loaded. In such cases, the string cached will be printed in both time columns.

  See also PYTHONPROFILEIMPORTTIME{.interpreted-text role="envvar"}.

  ::: versionadded 3.7 :::

  ::: versionchanged 3.14

  Added -X importtime=2 to also trace imports of loaded modules, and reserved values other than 1 and 2 for future use. :::

• -X dev: enable Python Development Mode <devmode>{.interpreted-text role="ref"}, introducing additional runtime checks that are too expensive to be enabled by default. See also PYTHONDEVMODE{.interpreted-text role="envvar"}.

  ::: versionadded 3.7 :::

• -X utf8 enables the Python UTF-8 Mode <utf8-mode>{.interpreted-text role="ref"}. -X utf8=0 explicitly disables Python UTF-8 Mode <utf8-mode>{.interpreted-text role="ref"} (even when it would otherwise activate automatically). See also PYTHONUTF8{.interpreted-text role="envvar"}.

  ::: versionadded 3.7 :::

• -X pycache_prefix=PATH enables writing .pyc files to a parallel tree rooted at the given directory instead of to the code tree. See also PYTHONPYCACHEPREFIX{.interpreted-text role="envvar"}.

  ::: versionadded 3.8 :::

• -X warn_default_encoding issues a EncodingWarning{.interpreted-text role="class"} when the locale-specific default encoding is used for opening files. See also PYTHONWARNDEFAULTENCODING{.interpreted-text role="envvar"}.

  ::: versionadded 3.10 :::

• -X no_debug_ranges disables the inclusion of the tables mapping extra location information (end line, start column offset and end column offset) to every instruction in code objects. This is useful when smaller code objects and pyc files are desired as well as suppressing the extra visual location indicators when the interpreter displays tracebacks. See also PYTHONNODEBUGRANGES{.interpreted-text role="envvar"}.

  ::: versionadded 3.11 :::

• -X frozen_modules determines whether or not frozen modules are ignored by the import machinery. A value of on means they get imported and off means they are ignored. The default is on if this is an installed Python (the normal case). If it's under development (running from the source tree) then the default is off. Note that the !importlib_bootstrap{.interpreted-text role="mod"} and !importlib_bootstrap_external{.interpreted-text role="mod"} frozen modules are always used, even if this flag is set to off. See also PYTHON_FROZEN_MODULES{.interpreted-text role="envvar"}.

  ::: versionadded 3.11 :::

• -X perf enables support for the Linux perf profiler. When this option is provided, the perf profiler will be able to report Python calls. This option is only available on some platforms and will do nothing if is not supported on the current system. The default value is "off". See also PYTHONPERFSUPPORT{.interpreted-text role="envvar"} and perf_profiling{.interpreted-text role="ref"}.

  ::: versionadded 3.12 :::

• -X perf_jit enables support for the Linux perf profiler with DWARF support. When this option is provided, the perf profiler will be able to report Python calls using DWARF information. This option is only available on some platforms and will do nothing if is not supported on the current system. The default value is "off". See also PYTHON_PERF_JIT_SUPPORT{.interpreted-text role="envvar"} and perf_profiling{.interpreted-text role="ref"}.

  ::: versionadded 3.13 :::

• -X disable_remote_debug disables the remote debugging support as described in 768{.interpreted-text role="pep"}. This includes both the functionality to schedule code for execution in another process and the functionality to receive code for execution in the current process.

  This option is only available on some platforms and will do nothing if is not supported on the current system. See also PYTHON_DISABLE_REMOTE_DEBUG{.interpreted-text role="envvar"} and 768{.interpreted-text role="pep"}.

  ::: versionadded 3.14 :::

• -X cpu_count={n}{.interpreted-text role="samp"} overrides os.cpu_count{.interpreted-text role="func"}, os.process_cpu_count{.interpreted-text role="func"}, and multiprocessing.cpu_count{.interpreted-text role="func"}. n must be greater than or equal to 1. This option may be useful for users who need to limit CPU resources of a container system. See also PYTHON_CPU_COUNT{.interpreted-text role="envvar"}. If n is default, nothing is overridden.

  ::: versionadded 3.13 :::

• -X presite={package.module}{.interpreted-text role="samp"} specifies a module that should be imported before the site{.interpreted-text role="mod"} module is executed and before the __main__{.interpreted-text role="mod"} module exists. Therefore, the imported module isn't __main__{.interpreted-text role="mod"}. This can be used to execute code early during Python initialization. Python needs to be built in debug mode <debug-build>{.interpreted-text role="ref"} for this option to exist. See also PYTHON_PRESITE{.interpreted-text role="envvar"}.

  ::: versionadded 3.13 :::

• -X gil={0,1}{.interpreted-text role="samp"} forces the GIL to be disabled or enabled, respectively. Setting to 0 is only available in builds configured with --disable-gil{.interpreted-text role="option"}. See also PYTHON_GIL{.interpreted-text role="envvar"} and whatsnew313-free-threaded-cpython{.interpreted-text role="ref"}.

  ::: versionadded 3.13 :::

• -X thread_inherit_context={0,1}{.interpreted-text role="samp"} causes ~threading.Thread{.interpreted-text role="class"} to, by default, use a copy of context of the caller of Thread.start() when starting. Otherwise, threads will start with an empty context. If unset, the value of this option defaults to 1 on free-threaded builds and to 0 otherwise. See also PYTHON_THREAD_INHERIT_CONTEXT{.interpreted-text role="envvar"}.

  ::: versionadded 3.14 :::

• -X context_aware_warnings={0,1}{.interpreted-text role="samp"} causes the warnings.catch_warnings{.interpreted-text role="class"} context manager to use a ~contextvars.ContextVar{.interpreted-text role="class"} to store warnings filter state. If unset, the value of this option defaults to 1 on free-threaded builds and to 0 otherwise. See also PYTHON_CONTEXT_AWARE_WARNINGS{.interpreted-text role="envvar"}.

  ::: versionadded 3.14 :::

• -X tlbc={0,1}{.interpreted-text role="samp"} enables (1, the default) or disables (0) thread-local bytecode in builds configured with --disable-gil{.interpreted-text role="option"}. When disabled, this also disables the specializing interpreter. See also PYTHON_TLBC{.interpreted-text role="envvar"}.

  ::: versionadded 3.14 :::

• -X lazy_imports={all,none,normal}{.interpreted-text role="samp"} controls lazy import behavior. all makes all imports lazy by default, none disables lazy imports entirely (even explicit lazy statements become eager), and normal (the default) respects the lazy keyword in source code. See also PYTHON_LAZY_IMPORTS{.interpreted-text role="envvar"}.

  ::: versionadded next :::

It also allows passing arbitrary values and retrieving them through the sys._xoptions{.interpreted-text role="data"} dictionary.

::: versionadded 3.2 :::

::: versionchanged 3.9 Removed the -X showalloccount option. :::

::: versionchanged 3.10 Removed the -X oldparser option. ::: ::::::

::: versionremoved 3.14

!-J{.interpreted-text role="option"} is no longer reserved for use by Jython, and now has no special meaning. :::

Controlling color {#using-on-controlling-color}

The Python interpreter is configured by default to use colors to highlight output in certain situations such as when displaying tracebacks. This behavior can be controlled by setting different environment variables.

Setting the environment variable TERM to dumb will disable color.

If the |FORCE_COLOR| environment variable is set, then color will be enabled regardless of the value of TERM. This is useful on CI systems which aren't terminals but can still display ANSI escape sequences.

If the |NO_COLOR| environment variable is set, Python will disable all color in the output. This takes precedence over FORCE_COLOR.

All these environment variables are used also by other tools to control color output. To control the color output only in the Python interpreter, the PYTHON_COLORS{.interpreted-text role="envvar"} environment variable can be used. This variable takes precedence over NO_COLOR, which in turn takes precedence over FORCE_COLOR.

Environment variables {#using-on-envvars}

These environment variables influence Python's behavior, they are processed before the command-line switches other than -E or -I. It is customary that command-line switches override environmental variables where there is a conflict.

::: envvar PYTHONHOME

Change the location of the standard Python libraries. By default, the libraries are searched in {prefix}/lib/python{version}{.interpreted-text role="file"} and {exec_prefix}/lib/python{version}{.interpreted-text role="file"}, where {prefix}{.interpreted-text role="file"} and {exec_prefix}{.interpreted-text role="file"} are installation-dependent directories, both defaulting to /usr/local{.interpreted-text role="file"}.

When PYTHONHOME{.interpreted-text role="envvar"} is set to a single directory, its value replaces both {prefix}{.interpreted-text role="file"} and {exec_prefix}{.interpreted-text role="file"}. To specify different values for these, set PYTHONHOME{.interpreted-text role="envvar"} to {prefix}:{exec_prefix}{.interpreted-text role="file"}. :::

::: envvar PYTHONPATH

Augment the default search path for module files. The format is the same as the shell's PATH{.interpreted-text role="envvar"}: one or more directory pathnames separated by os.pathsep{.interpreted-text role="data"} (e.g. colons on Unix or semicolons on Windows). Non-existent directories are silently ignored.

In addition to normal directories, individual PYTHONPATH{.interpreted-text role="envvar"} entries may refer to zipfiles containing pure Python modules (in either source or compiled form). Extension modules cannot be imported from zipfiles.

The default search path is installation dependent, but generally begins with {prefix}/lib/python{version}{.interpreted-text role="file"} (see PYTHONHOME{.interpreted-text role="envvar"} above). It is always appended to PYTHONPATH{.interpreted-text role="envvar"}.

An additional directory will be inserted in the search path in front of PYTHONPATH{.interpreted-text role="envvar"} as described above under using-on-interface-options{.interpreted-text role="ref"}. The search path can be manipulated from within a Python program as the variable sys.path{.interpreted-text role="data"}. :::

:::: envvar PYTHONSAFEPATH

If this is set to a non-empty string, don't prepend a potentially unsafe path to sys.path{.interpreted-text role="data"}: see the -P{.interpreted-text role="option"} option for details.

::: versionadded 3.11 ::: ::::

:::: envvar PYTHONPLATLIBDIR

If this is set to a non-empty string, it overrides the sys.platlibdir{.interpreted-text role="data"} value.

::: versionadded 3.9 ::: ::::

:::: envvar PYTHONSTARTUP

If this is the name of a readable file, the Python commands in that file are executed before the first prompt is displayed in interactive mode. The file is executed in the same namespace where interactive commands are executed so that objects defined or imported in it can be used without qualification in the interactive session. You can also change the prompts sys.ps1{.interpreted-text role="data"} and sys.ps2{.interpreted-text role="data"} and the hook sys.__interactivehook__{.interpreted-text role="data"} in this file.

::: audit-event cpython.run_startup filename envvar-PYTHONSTARTUP

Raises an auditing event <auditing>{.interpreted-text role="ref"} cpython.run_startup with the filename as the argument when called on startup. ::: ::::

::: envvar PYTHONOPTIMIZE

If this is set to a non-empty string it is equivalent to specifying the -O{.interpreted-text role="option"} option. If set to an integer, it is equivalent to specifying -O{.interpreted-text role="option"} multiple times. :::

:::: envvar PYTHONBREAKPOINT

If this is set, it names a callable using dotted-path notation. The module containing the callable will be imported and then the callable will be run by the default implementation of sys.breakpointhook{.interpreted-text role="func"} which itself is called by built-in breakpoint{.interpreted-text role="func"}. If not set, or set to the empty string, it is equivalent to the value "pdb.set_trace". Setting this to the string "0" causes the default implementation of sys.breakpointhook{.interpreted-text role="func"} to do nothing but return immediately.

::: versionadded 3.7 ::: ::::

::: envvar PYTHONDEBUG

If this is set to a non-empty string it is equivalent to specifying the -d{.interpreted-text role="option"} option. If set to an integer, it is equivalent to specifying -d{.interpreted-text role="option"} multiple times.

This environment variable requires a debug build of Python <debug-build>{.interpreted-text role="ref"}, otherwise it's ignored. :::

:::::: envvar PYTHONINSPECT

If this is set to a non-empty string it is equivalent to specifying the -i{.interpreted-text role="option"} option.

This variable can also be modified by Python code using os.environ{.interpreted-text role="data"} to force inspect mode on program termination.

::: audit-event cpython.run_stdin "" "" :::

::: versionchanged 3.12.5 (also 3.11.10, 3.10.15, 3.9.20, and 3.8.20) Emits audit events. :::

::: versionchanged 3.13 Uses PyREPL if possible, in which case PYTHONSTARTUP{.interpreted-text role="envvar"} is also executed. Emits audit events. ::: ::::::

::: envvar PYTHONUNBUFFERED

If this is set to a non-empty string it is equivalent to specifying the -u{.interpreted-text role="option"} option. :::

::: envvar PYTHONVERBOSE

If this is set to a non-empty string it is equivalent to specifying the -v{.interpreted-text role="option"} option. If set to an integer, it is equivalent to specifying -v{.interpreted-text role="option"} multiple times. :::

::: envvar PYTHONCASEOK

If this is set, Python ignores case in import{.interpreted-text role="keyword"} statements. This only works on Windows and macOS. :::

::: envvar PYTHONDONTWRITEBYTECODE

If this is set to a non-empty string, Python won't try to write .pyc files on the import of source modules. This is equivalent to specifying the -B{.interpreted-text role="option"} option. :::

:::: envvar PYTHONPYCACHEPREFIX

If this is set, Python will write .pyc files in a mirror directory tree at this path, instead of in __pycache__ directories within the source tree. This is equivalent to specifying the -X{.interpreted-text role="option"} pycache_prefix=PATH option.

::: versionadded 3.8 ::: ::::

:::: envvar PYTHONHASHSEED

If this variable is not set or set to random, a random value is used to seed the hashes of str and bytes objects.

If PYTHONHASHSEED{.interpreted-text role="envvar"} is set to an integer value, it is used as a fixed seed for generating the hash() of the types covered by the hash randomization.

Its purpose is to allow repeatable hashing, such as for selftests for the interpreter itself, or to allow a cluster of python processes to share hash values.

The integer must be a decimal number in the range [0,4294967295]. Specifying the value 0 will disable hash randomization.

::: versionadded 3.2.3 ::: ::::

:::: envvar PYTHONINTMAXSTRDIGITS

If this variable is set to an integer, it is used to configure the interpreter's global integer string conversion length limitation <int_max_str_digits>{.interpreted-text role="ref"}.

::: versionadded 3.11 ::: ::::

::::: envvar PYTHONIOENCODING

If this is set before running the interpreter, it overrides the encoding used for stdin/stdout/stderr, in the syntax encodingname:errorhandler. Both the encodingname and the :errorhandler parts are optional and have the same meaning as in str.encode{.interpreted-text role="func"}.

For stderr, the :errorhandler part is ignored; the handler will always be 'backslashreplace'.

::: versionchanged 3.4 The encodingname part is now optional. :::

::: versionchanged 3.6 On Windows, the encoding specified by this variable is ignored for interactive console buffers unless PYTHONLEGACYWINDOWSSTDIO{.interpreted-text role="envvar"} is also specified. Files and pipes redirected through the standard streams are not affected. ::: :::::

:::: envvar PYTHONNOUSERSITE

If this is set, Python won't add the user site-packages directory <site.USER_SITE>{.interpreted-text role="data"} to sys.path{.interpreted-text role="data"}.

::: seealso 370{.interpreted-text role="pep"} -- Per user site-packages directory ::: ::::

:::: envvar PYTHONUSERBASE

Defines the user base directory <site.USER_BASE>{.interpreted-text role="data"}, which is used to compute the path of the user site-packages directory <site.USER_SITE>{.interpreted-text role="data"} and installation paths <sysconfig-user-scheme>{.interpreted-text role="ref"} for python -m pip install --user.

::: seealso 370{.interpreted-text role="pep"} -- Per user site-packages directory ::: ::::

::: envvar PYTHONEXECUTABLE

If this environment variable is set, sys.argv[0] will be set to its value instead of the value got through the C runtime. Only works on macOS. :::

:::: envvar PYTHONWARNINGS

This is equivalent to the -W{.interpreted-text role="option"} option. If set to a comma separated string, it is equivalent to specifying -W{.interpreted-text role="option"} multiple times, with filters later in the list taking precedence over those earlier in the list.

The simplest settings apply a particular action unconditionally to all warnings emitted by a process (even those that are otherwise ignored by default):

PYTHONWARNINGS=default  # Warn once per call location
PYTHONWARNINGS=error    # Convert to exceptions
PYTHONWARNINGS=always   # Warn every time
PYTHONWARNINGS=all      # Same as PYTHONWARNINGS=always
PYTHONWARNINGS=module   # Warn once per calling module
PYTHONWARNINGS=once     # Warn once per Python process
PYTHONWARNINGS=ignore   # Never warn

See warning-filter{.interpreted-text role="ref"} and describing-warning-filters{.interpreted-text role="ref"} for more details.

::: versionchanged 3.15 Added regular expression support for message and module. ::: ::::

:::: envvar PYTHONFAULTHANDLER

If this environment variable is set to a non-empty string, faulthandler.enable{.interpreted-text role="func"} is called at startup: install a handler for ~signal.SIGSEGV{.interpreted-text role="const"}, ~signal.SIGFPE{.interpreted-text role="const"}, ~signal.SIGABRT{.interpreted-text role="const"}, ~signal.SIGBUS{.interpreted-text role="const"} and ~signal.SIGILL{.interpreted-text role="const"} signals to dump the Python traceback. This is equivalent to -X{.interpreted-text role="option"} faulthandler option.

::: versionadded 3.3 ::: ::::

:::: envvar PYTHONTRACEMALLOC

If this environment variable is set to a non-empty string, start tracing Python memory allocations using the tracemalloc{.interpreted-text role="mod"} module. The value of the variable is the maximum number of frames stored in a traceback of a trace. For example, PYTHONTRACEMALLOC=1 stores only the most recent frame. See the tracemalloc.start{.interpreted-text role="func"} function for more information. This is equivalent to setting the -X{.interpreted-text role="option"} tracemalloc option.

::: versionadded 3.4 ::: ::::

::::: envvar PYTHONPROFILEIMPORTTIME

If this environment variable is set to 1, Python will show how long each import takes. If set to 2, Python will include output for imported modules that have already been loaded. This is equivalent to setting the -X{.interpreted-text role="option"} importtime option.

::: versionadded 3.7 :::

::: versionchanged 3.14

Added PYTHONPROFILEIMPORTTIME=2 to also trace imports of loaded modules. ::: :::::

:::: envvar PYTHONASYNCIODEBUG

If this environment variable is set to a non-empty string, enable the debug mode <asyncio-debug-mode>{.interpreted-text role="ref"} of the asyncio{.interpreted-text role="mod"} module.

::: versionadded 3.4 ::: ::::

::::: envvar PYTHONMALLOC

Set the Python memory allocators and/or install debug hooks.

Set the family of memory allocators used by Python:

• default: use the default memory allocators <default-memory-allocators>{.interpreted-text role="ref"}.
• malloc: use the malloc{.interpreted-text role="c:func"} function of the C library for all domains (PYMEM_DOMAIN_RAW{.interpreted-text role="c:macro"}, PYMEM_DOMAIN_MEM{.interpreted-text role="c:macro"}, PYMEM_DOMAIN_OBJ{.interpreted-text role="c:macro"}).
• pymalloc: use the pymalloc allocator <pymalloc>{.interpreted-text role="ref"} for PYMEM_DOMAIN_MEM{.interpreted-text role="c:macro"} and PYMEM_DOMAIN_OBJ{.interpreted-text role="c:macro"} domains and use the malloc{.interpreted-text role="c:func"} function for the PYMEM_DOMAIN_RAW{.interpreted-text role="c:macro"} domain.
• mimalloc: use the mimalloc allocator <mimalloc>{.interpreted-text role="ref"} for PYMEM_DOMAIN_MEM{.interpreted-text role="c:macro"} and PYMEM_DOMAIN_OBJ{.interpreted-text role="c:macro"} domains and use the malloc{.interpreted-text role="c:func"} function for the PYMEM_DOMAIN_RAW{.interpreted-text role="c:macro"} domain.

Install debug hooks <pymem-debug-hooks>{.interpreted-text role="ref"}:

• debug: install debug hooks on top of the default memory allocators <default-memory-allocators>{.interpreted-text role="ref"}.
• malloc_debug: same as malloc but also install debug hooks.
• pymalloc_debug: same as pymalloc but also install debug hooks.
• mimalloc_debug: same as mimalloc but also install debug hooks.

::: versionadded 3.6 :::

::: versionchanged 3.7 Added the "default" allocator. ::: :::::

:::: envvar PYTHONMALLOCSTATS

If set to a non-empty string, Python will print statistics of the pymalloc memory allocator <pymalloc>{.interpreted-text role="ref"} every time a new pymalloc object arena is created, and on shutdown.

This variable is ignored if the PYTHONMALLOC{.interpreted-text role="envvar"} environment variable is used to force the malloc{.interpreted-text role="c:func"} allocator of the C library, or if Python is configured without pymalloc support.

::: versionchanged 3.6 This variable can now also be used on Python compiled in release mode. It now has no effect if set to an empty string. ::: ::::

:::::: envvar PYTHON_PYMALLOC_HUGEPAGES

If set to a non-zero integer, enable huge page support for pymalloc <pymalloc>{.interpreted-text role="ref"} arenas. Set to 0 or unset to disable. Python must be compiled with --with-pymalloc-hugepages{.interpreted-text role="option"} for this variable to have any effect.

When enabled, arena allocation uses MAP_HUGETLB (Linux) or MEM_LARGE_PAGES (Windows) with automatic fallback to regular pages if huge pages are not available.

:::: warning ::: title Warning :::

On Linux, if the huge-page pool is exhausted, page faults --- including copy-on-write faults triggered by os.fork{.interpreted-text role="func"} --- deliver SIGBUS and kill the process. Only enable this in environments where the huge-page pool is properly sized and fork-safety is not a concern. ::::

::: versionadded 3.15 ::: ::::::

::::: envvar PYTHONLEGACYWINDOWSFSENCODING

If set to a non-empty string, the default filesystem encoding and error handler{.interpreted-text role="term"} mode will revert to their pre-3.6 values of 'mbcs' and 'replace', respectively. Otherwise, the new defaults 'utf-8' and 'surrogatepass' are used.

This may also be enabled at runtime with sys._enablelegacywindowsfsencoding{.interpreted-text role="func"}.

::: availability Windows. :::

::: versionadded 3.6 See 529{.interpreted-text role="pep"} for more details. ::: :::::

::::: envvar PYTHONLEGACYWINDOWSSTDIO

If set to a non-empty string, does not use the new console reader and writer. This means that Unicode characters will be encoded according to the active console code page, rather than using utf-8.

This variable is ignored if the standard streams are redirected (to files or pipes) rather than referring to console buffers.

::: availability Windows. :::

::: versionadded 3.6 ::: :::::

::::: envvar PYTHONCOERCECLOCALE

If set to the value 0, causes the main Python command line application to skip coercing the legacy ASCII-based C and POSIX locales to a more capable UTF-8 based alternative.

If this variable is not set (or is set to a value other than 0), the LC_ALL locale override environment variable is also not set, and the current locale reported for the LC_CTYPE category is either the default C locale, or else the explicitly ASCII-based POSIX locale, then the Python CLI will attempt to configure the following locales for the LC_CTYPE category in the order listed before loading the interpreter runtime:

• C.UTF-8
• C.utf8
• UTF-8

If setting one of these locale categories succeeds, then the LC_CTYPE environment variable will also be set accordingly in the current process environment before the Python runtime is initialized. This ensures that in addition to being seen by both the interpreter itself and other locale-aware components running in the same process (such as the GNU readline library), the updated setting is also seen in subprocesses (regardless of whether or not those processes are running a Python interpreter), as well as in operations that query the environment rather than the current C locale (such as Python's own locale.getdefaultlocale{.interpreted-text role="func"}).

Configuring one of these locales (either explicitly or via the above implicit locale coercion) automatically enables the surrogateescape error handler <error-handlers>{.interpreted-text role="ref"} for sys.stdin{.interpreted-text role="data"} and sys.stdout{.interpreted-text role="data"} (sys.stderr{.interpreted-text role="data"} continues to use backslashreplace as it does in any other locale). This stream handling behavior can be overridden using PYTHONIOENCODING{.interpreted-text role="envvar"} as usual.

For debugging purposes, setting PYTHONCOERCECLOCALE=warn will cause Python to emit warning messages on stderr if either the locale coercion activates, or else if a locale that would have triggered coercion is still active when the Python runtime is initialized.

Also note that even when locale coercion is disabled, or when it fails to find a suitable target locale, PYTHONUTF8{.interpreted-text role="envvar"} will still activate by default in legacy ASCII-based locales. Both features must be disabled in order to force the interpreter to use ASCII instead of UTF-8 for system interfaces.

::: availability Unix. :::

::: versionadded 3.7 See 538{.interpreted-text role="pep"} for more details. ::: :::::

:::: envvar PYTHONDEVMODE

If this environment variable is set to a non-empty string, enable Python Development Mode <devmode>{.interpreted-text role="ref"}, introducing additional runtime checks that are too expensive to be enabled by default. This is equivalent to setting the -X{.interpreted-text role="option"} dev option.

::: versionadded 3.7 ::: ::::

:::: envvar PYTHONUTF8

If set to 1, enable the Python UTF-8 Mode <utf8-mode>{.interpreted-text role="ref"}.

If set to 0, disable the Python UTF-8 Mode <utf8-mode>{.interpreted-text role="ref"}.

Setting any other non-empty string causes an error during interpreter initialisation.

::: versionadded 3.7 ::: ::::

:::: envvar PYTHONWARNDEFAULTENCODING

If this environment variable is set to a non-empty string, issue a EncodingWarning{.interpreted-text role="class"} when the locale-specific default encoding is used.

See io-encoding-warning{.interpreted-text role="ref"} for details.

::: versionadded 3.10 ::: ::::

:::: envvar PYTHONNODEBUGRANGES

If this variable is set, it disables the inclusion of the tables mapping extra location information (end line, start column offset and end column offset) to every instruction in code objects. This is useful when smaller code objects and pyc files are desired as well as suppressing the extra visual location indicators when the interpreter displays tracebacks.

::: versionadded 3.11 ::: ::::

:::: envvar PYTHONPERFSUPPORT

If this variable is set to a nonzero value, it enables support for the Linux perf profiler so Python calls can be detected by it.

If set to 0, disable Linux perf profiler support.

See also the -X perf <-X>{.interpreted-text role="option"} command-line option and perf_profiling{.interpreted-text role="ref"}.

::: versionadded 3.12 ::: ::::

:::: envvar PYTHON_PERF_JIT_SUPPORT

If this variable is set to a nonzero value, it enables support for the Linux perf profiler so Python calls can be detected by it using DWARF information.

If set to 0, disable Linux perf profiler support.

See also the -X perf_jit <-X>{.interpreted-text role="option"} command-line option and perf_profiling{.interpreted-text role="ref"}.

::: versionadded 3.13 ::: ::::

:::: envvar PYTHON_DISABLE_REMOTE_DEBUG

If this variable is set to a non-empty string, it disables the remote debugging feature described in 768{.interpreted-text role="pep"}. This includes both the functionality to schedule code for execution in another process and the functionality to receive code for execution in the current process.

See also the -X disable_remote_debug{.interpreted-text role="option"} command-line option.

::: versionadded 3.14 ::: ::::

:::: envvar PYTHON_CPU_COUNT

If this variable is set to a positive integer, it overrides the return values of os.cpu_count{.interpreted-text role="func"} and os.process_cpu_count{.interpreted-text role="func"}.

See also the -X cpu_count <-X>{.interpreted-text role="option"} command-line option.

::: versionadded 3.13 ::: ::::

:::: envvar PYTHON_FROZEN_MODULES

If this variable is set to on or off, it determines whether or not frozen modules are ignored by the import machinery. A value of on means they get imported and off means they are ignored. The default is on for non-debug builds (the normal case) and off for debug builds. Note that the !importlib_bootstrap{.interpreted-text role="mod"} and !importlib_bootstrap_external{.interpreted-text role="mod"} frozen modules are always used, even if this flag is set to off.

See also the -X frozen_modules <-X>{.interpreted-text role="option"} command-line option.

::: versionadded 3.13 ::: ::::

:::: envvar PYTHON_COLORS

If this variable is set to 1, the interpreter will colorize various kinds of output. Setting it to 0 deactivates this behavior. See also using-on-controlling-color{.interpreted-text role="ref"}.

::: versionadded 3.13 ::: ::::

:::: envvar PYTHON_BASIC_REPL

If this variable is set to any value, the interpreter will not attempt to load the Python-based REPL{.interpreted-text role="term"} that requires readline{.interpreted-text role="mod"}, and will instead use the traditional parser-based REPL{.interpreted-text role="term"}.

::: versionadded 3.13 ::: ::::

:::: envvar PYTHON_HISTORY

This environment variable can be used to set the location of a .python_history file (by default, it is .python_history in the user's home directory).

::: versionadded 3.13 ::: ::::

:::: envvar PYTHON_GIL

If this variable is set to 1, the global interpreter lock (GIL) will be forced on. Setting it to 0 forces the GIL off (needs Python configured with the --disable-gil{.interpreted-text role="option"} build option).

See also the -X gil <-X>{.interpreted-text role="option"} command-line option, which takes precedence over this variable, and whatsnew313-free-threaded-cpython{.interpreted-text role="ref"}.

::: versionadded 3.13 ::: ::::

:::: envvar PYTHON_THREAD_INHERIT_CONTEXT

If this variable is set to 1 then ~threading.Thread{.interpreted-text role="class"} will, by default, use a copy of context of the caller of Thread.start() when starting. Otherwise, new threads will start with an empty context. If unset, this variable defaults to 1 on free-threaded builds and to 0 otherwise. See also -X thread_inherit_context<-X>{.interpreted-text role="option"}.

::: versionadded 3.14 ::: ::::

:::: envvar PYTHON_CONTEXT_AWARE_WARNINGS

If set to 1 then the warnings.catch_warnings{.interpreted-text role="class"} context manager will use a ~contextvars.ContextVar{.interpreted-text role="class"} to store warnings filter state. If unset, this variable defaults to 1 on free-threaded builds and to 0 otherwise. See -X context_aware_warnings<-X>{.interpreted-text role="option"}.

::: versionadded 3.14 ::: ::::

:::: envvar PYTHON_JIT

On builds where experimental just-in-time compilation is available, this variable can force the JIT to be disabled (0) or enabled (1) at interpreter startup.

::: versionadded 3.13 ::: ::::

:::: envvar PYTHON_TLBC

If set to 1 enables thread-local bytecode. If set to 0 thread-local bytecode and the specializing interpreter are disabled. Only applies to builds configured with --disable-gil{.interpreted-text role="option"}.

See also the -X tlbc <-X>{.interpreted-text role="option"} command-line option.

::: versionadded 3.14 ::: ::::

:::: envvar PYTHON_LAZY_IMPORTS

Controls lazy import behavior. Accepts three values: all makes all imports lazy by default, none disables lazy imports entirely (even explicit lazy statements become eager), and normal (the default) respects the lazy keyword in source code.

See also the -X lazy_imports <-X>{.interpreted-text role="option"} command-line option.

::: versionadded next ::: ::::

Debug-mode variables

::: envvar PYTHONDUMPREFS

If set, Python will dump objects and reference counts still alive after shutting down the interpreter.

Needs Python configured with the --with-trace-refs{.interpreted-text role="option"} build option. :::

:::: envvar PYTHONDUMPREFSFILE

If set, Python will dump objects and reference counts still alive after shutting down the interpreter into a file under the path given as the value to this environment variable.

Needs Python configured with the --with-trace-refs{.interpreted-text role="option"} build option.

::: versionadded 3.11 ::: ::::

:::: envvar PYTHON_PRESITE

If this variable is set to a module, that module will be imported early in the interpreter lifecycle, before the site{.interpreted-text role="mod"} module is executed, and before the __main__{.interpreted-text role="mod"} module is created. Therefore, the imported module is not treated as __main__{.interpreted-text role="mod"}.

This can be used to execute code early during Python initialization.

To import a submodule, use package.module as the value, like in an import statement.

See also the -X presite <-X>{.interpreted-text role="option"} command-line option, which takes precedence over this variable.

Needs Python configured with the --with-pydebug{.interpreted-text role="option"} build option.

::: versionadded 3.13 ::: ::::