FindPython3

New in version 3.12.

Find Python 3 interpreter, compiler and development environment (include directories and libraries).

When a version is requested, it can be specified as a simple value or as a range. For a detailed description of version range usage and capabilities, refer to the find_package() command.

The following components are supported:

  • Interpreter: search for Python 3 interpreter

  • Compiler: search for Python 3 compiler. Only offered by IronPython.

  • Development: search for development artifacts (include directories and libraries). This component includes two sub-components which can be specified independently:

    • Development.Module: search for artifacts for Python 3 module developments.

    • Development.Embed: search for artifacts for Python 3 embedding developments.

  • NumPy: search for NumPy include directories.

If no COMPONENTS are specified, Interpreter is assumed.

If component Development is specified, it implies sub-components Development.Module and Development.Embed.

To ensure consistent versions between components Interpreter, Compiler, Development (or one of its sub-components) and NumPy, specify all components at the same time:

find_package (Python3 COMPONENTS Interpreter Development)

This module looks only for version 3 of Python. This module can be used concurrently with FindPython2 module to use both Python versions.

The FindPython module can be used if Python version does not matter for you.

Note

If components Interpreter and Development (or one of its sub-components) are both specified, this module search only for interpreter with same platform architecture as the one defined by CMake configuration. This constraint does not apply if only Interpreter component is specified.

Imported Targets

This module defines the following Imported Targets (when CMAKE_ROLE is PROJECT):

Python3::Interpreter

Python 3 interpreter. Target defined if component Interpreter is found.

Python3::Compiler

Python 3 compiler. Target defined if component Compiler is found.

Python3::Module

Python 3 library for Python module. Target defined if component Development.Module is found.

Python3::Python

Python 3 library for Python embedding. Target defined if component Development.Embed is found.

Python3::NumPy

NumPy library for Python 3. Target defined if component NumPy is found.

Result Variables

This module will set the following variables in your project (see Standard Variable Names):

Python3_FOUND

System has the Python 3 requested components.

Python3_Interpreter_FOUND

System has the Python 3 interpreter.

Python3_EXECUTABLE

Path to the Python 3 interpreter.

Python3_INTERPRETER_ID
A short string unique to the interpreter. Possible values include:

  • Python

  • ActivePython

  • Anaconda

  • Canopy

  • IronPython

  • PyPy

Python3_STDLIB

Standard platform independent installation directory.

Information returned by distutils.sysconfig.get_python_lib(plat_specific=False,standard_lib=True) or else sysconfig.get_path('stdlib').

Python3_STDARCH

Standard platform dependent installation directory.

Information returned by distutils.sysconfig.get_python_lib(plat_specific=True,standard_lib=True) or else sysconfig.get_path('platstdlib').

Python3_SITELIB

Third-party platform independent installation directory.

Information returned by distutils.sysconfig.get_python_lib(plat_specific=False,standard_lib=False) or else sysconfig.get_path('purelib').

Python3_SITEARCH

Third-party platform dependent installation directory.

Information returned by distutils.sysconfig.get_python_lib(plat_specific=True,standard_lib=False) or else sysconfig.get_path('platlib').

Python3_SOABI

Extension suffix for modules.

Information returned by distutils.sysconfig.get_config_var('SOABI') or computed from distutils.sysconfig.get_config_var('EXT_SUFFIX') or python3-config --extension-suffix. If package distutils.sysconfig is not available, sysconfig.get_config_var('SOABI') or sysconfig.get_config_var('EXT_SUFFIX') are used.

Python3_Compiler_FOUND

System has the Python 3 compiler.

Python3_COMPILER

Path to the Python 3 compiler. Only offered by IronPython.

Python3_COMPILER_ID
A short string unique to the compiler. Possible values include:

  • IronPython

Python3_DOTNET_LAUNCHER

The .Net interpreter. Only used by IronPython implementation.

Python3_Development_FOUND

System has the Python 3 development artifacts.

Python3_Development.Module_FOUND

System has the Python 3 development artifacts for Python module.

Python3_Development.Embed_FOUND

System has the Python 3 development artifacts for Python embedding.

Python3_INCLUDE_DIRS

The Python 3 include directories.

Python3_LINK_OPTIONS

The Python 3 link options. Some configurations require specific link options for a correct build and execution.

Python3_LIBRARIES

The Python 3 libraries.

Python3_LIBRARY_DIRS

The Python 3 library directories.

Python3_RUNTIME_LIBRARY_DIRS

The Python 3 runtime library directories.

Python3_VERSION

Python 3 version.

Python3_VERSION_MAJOR

Python 3 major version.

Python3_VERSION_MINOR

Python 3 minor version.

Python3_VERSION_PATCH

Python 3 patch version.

Python3_PyPy_VERSION

Python 3 PyPy version.

Python3_NumPy_FOUND

System has the NumPy.

Python3_NumPy_INCLUDE_DIRS

The NumPy include directories.

Python3_NumPy_VERSION

The NumPy version.

Hints

Python3_ROOT_DIR

Define the root directory of a Python 3 installation.

Python3_USE_STATIC_LIBS

  • If not defined, search for shared libraries and static libraries in that order.

  • If set to TRUE, search only for static libraries.

  • If set to FALSE, search only for shared libraries.

Python3_FIND_ABI

This variable defines which ABIs, as defined in PEP 3149, should be searched.

Note

If Python3_FIND_ABI is not defined, any ABI will be searched.

The Python3_FIND_ABI variable is a 3-tuple specifying, in that order, pydebug (d), pymalloc (m) and unicode (u) flags. Each element can be set to one of the following:

  • ON: Corresponding flag is selected.

  • OFF: Corresponding flag is not selected.

  • ANY: The two possibilities (ON and OFF) will be searched.

From this 3-tuple, various ABIs will be searched starting from the most specialized to the most general. Moreover, debug versions will be searched after non-debug ones.

For example, if we have:

set (Python3_FIND_ABI "ON" "ANY" "ANY")

The following flags combinations will be appended, in that order, to the artifact names: dmu, dm, du, and d.

And to search any possible ABIs:

set (Python3_FIND_ABI "ANY" "ANY" "ANY")

The following combinations, in that order, will be used: mu, m, u, <empty>, dmu, dm, du and d.

Note

This hint is useful only on POSIX systems. So, on Windows systems, when Python3_FIND_ABI is defined, Python distributions from python.org will be found only if value for each flag is OFF or ANY.

Python3_FIND_STRATEGY

This variable defines how lookup will be done. The Python3_FIND_STRATEGY variable can be set to one of the following:

  • VERSION: Try to find the most recent version in all specified locations. This is the default if policy CMP0094 is undefined or set to OLD.

  • LOCATION: Stops lookup as soon as a version satisfying version constraints is founded. This is the default if policy CMP0094 is set to NEW.

Python3_FIND_REGISTRY

On Windows the Python3_FIND_REGISTRY variable determine the order of preference between registry and environment variables. The Python3_FIND_REGISTRY variable can be set to one of the following:

  • FIRST: Try to use registry before environment variables. This is the default.

  • LAST: Try to use registry after environment variables.

  • NEVER: Never try to use registry.

Python3_FIND_FRAMEWORK

On macOS the Python3_FIND_FRAMEWORK variable determine the order of preference between Apple-style and unix-style package components. This variable can take same values as CMAKE_FIND_FRAMEWORK variable.

Note

Value ONLY is not supported so FIRST will be used instead.

If Python3_FIND_FRAMEWORK is not defined, CMAKE_FIND_FRAMEWORK variable will be used, if any.

Python3_FIND_VIRTUALENV

This variable defines the handling of virtual environments managed by virtualenv or conda. It is meaningful only when a virtual environment is active (i.e. the activate script has been evaluated). In this case, it takes precedence over Python3_FIND_REGISTRY and CMAKE_FIND_FRAMEWORK variables. The Python3_FIND_VIRTUALENV variable can be set to one of the following:

  • FIRST: The virtual environment is used before any other standard paths to look-up for the interpreter. This is the default.

  • ONLY: Only the virtual environment is used to look-up for the interpreter.

  • STANDARD: The virtual environment is not used to look-up for the interpreter but environment variable PATH is always considered. In this case, variable Python3_FIND_REGISTRY (Windows) or CMAKE_FIND_FRAMEWORK (macOS) can be set with value LAST or NEVER to select preferably the interpreter from the virtual environment.

Note

If the component Development is requested, it is strongly recommended to also include the component Interpreter to get expected result.

Python3_FIND_IMPLEMENTATIONS

This variable defines, in an ordered list, the different implementations which will be searched. The Python3_FIND_IMPLEMENTATIONS variable can hold the following values:

  • CPython: this is the standard implementation. Various products, like Anaconda or ActivePython, rely on this implementation.

  • IronPython: This implementation use the CSharp language for .NET Framework on top of the Dynamic Language Runtime (DLR). See IronPython.

  • PyPy: This implementation use RPython language and RPython translation toolchain to produce the python interpreter. See PyPy.

The default value is:

  • Windows platform: CPython, IronPython

  • Other platforms: CPython

Note

This hint has the lowest priority of all hints, so even if, for example, you specify IronPython first and CPython in second, a python product based on CPython can be selected because, for example with Python3_FIND_STRATEGY=LOCATION, each location will be search first for IronPython and second for CPython.

Note

When IronPython is specified, on platforms other than Windows, the .Net interpreter (i.e. mono command) is expected to be available through the PATH variable.

Artifacts Specification

To solve special cases, it is possible to specify directly the artifacts by setting the following variables:

Python3_EXECUTABLE

The path to the interpreter.

Python3_COMPILER

The path to the compiler.

Python3_DOTNET_LAUNCHER

The .Net interpreter. Only used by IronPython implementation.

Python3_LIBRARY

The path to the library. It will be used to compute the variables Python3_LIBRARIES, Python3_LIBRARY_DIRS and Python3_RUNTIME_LIBRARY_DIRS.

Python3_INCLUDE_DIR

The path to the directory of the Python headers. It will be used to compute the variable Python3_INCLUDE_DIRS.

Python3_NumPy_INCLUDE_DIR

The path to the directory of the NumPy headers. It will be used to compute the variable Python3_NumPy_INCLUDE_DIRS.

Note

All paths must be absolute. Any artifact specified with a relative path will be ignored.

Note

When an artifact is specified, all HINTS will be ignored and no search will be performed for this artifact.

If more than one artifact is specified, it is the user’s responsibility to ensure the consistency of the various artifacts.

By default, this module supports multiple calls in different directories of a project with different version/component requirements while providing correct and consistent results for each call. To support this behavior, CMake cache is not used in the traditional way which can be problematic for interactive specification. So, to enable also interactive specification, module behavior can be controlled with the following variable:

Python3_ARTIFACTS_INTERACTIVE

Selects the behavior of the module. This is a boolean variable:

  • If set to TRUE: Create CMake cache entries for the above artifact specification variables so that users can edit them interactively. This disables support for multiple version/component requirements.

  • If set to FALSE or undefined: Enable multiple version/component requirements.

Commands

This module defines the command Python3_add_library (when CMAKE_ROLE is PROJECT), which has the same semantics as add_library() and adds a dependency to target Python3::Python or, when library type is MODULE, to target Python3::Module and takes care of Python module naming rules:

Python3_add_library (<name> [STATIC | SHARED | MODULE [WITH_SOABI]]
                     <source1> [<source2> ...])

If the library type is not specified, MODULE is assumed.

For MODULE library type, if option WITH_SOABI is specified, the module suffix will include the Python3_SOABI value, if any.