# FindPython

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

The following components are supported:

- `Interpreter`: search for Python interpreter.

- `Compiler`: search for Python 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 module developments.

  - `Development.Embed`: search for artifacts for Python 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 (Python COMPONENTS Interpreter Development)

This module looks preferably for version 3 of Python. If not found, version 2 is searched. To manage concurrent versions 3 and 2 of Python, use `FindPython3` and `FindPython2` modules rather than this one.

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 contraint does not apply if only `Interpreter` component is specified.

## Imported Targets

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

`Python::Interpreter`

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

`Python::Compiler`

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

`Python::Module`

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

`Python::Python`

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

`Python::NumPy`

  NumPy Python library. Target defined if component `NumPy` is found.

## Result Variables

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

`Python_FOUND`

  System has the Python requested components.

`Python_Interpreter_FOUND`

  System has the Python interpreter.

`Python_EXECUTABLE`

  Path to the Python interpreter.

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

    - Python

    - ActivePython

    - Anaconda

    - Canopy

    - IronPython

    - PyPy

`Python_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')`.

`Python_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')`.

`Python_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')`.

`Python_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')`.

`Python_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 `python-config --extension-suffix`. If package `distutils.sysconfig` is not available, `sysconfig.get_config_var('SOABI')` or `sysconfig.get_config_var('EXT_SUFFIX')` are used.

`Python_Compiler_FOUND`

  System has the Python compiler.

`Python_COMPILER`

  Path to the Python compiler. Only offered by IronPython.

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

    - IronPython

`Python_DOTNET_LAUNCHER`

  The `.Net` interpreter. Only used by `IronPython` implementation.

`Python_Development_FOUND`

  System has the Python development artifacts.

`Python_Development.Module_FOUND`

  System has the Python development artifacts for Python module.

`Python_Development.Embed_FOUND`

  System has the Python development artifacts for Python embedding.

`Python_INCLUDE_DIRS`

  The Python include directories.

`Python_LIBRARIES`

  The Python libraries.

`Python_LIBRARY_DIRS`

  The Python library directories.

`Python_RUNTIME_LIBRARY_DIRS`

  The Python runtime library directories.

`Python_VERSION`

  Python version.

`Python_VERSION_MAJOR`

  Python major version.

`Python_VERSION_MINOR`

  Python minor version.

`Python_VERSION_PATCH`

  Python patch version.

`Python_PyPy_VERSION`

  Python PyPy version.

`Python_NumPy_FOUND`

  System has the NumPy.

`Python_NumPy_INCLUDE_DIRS`

  The NumPy include directries.

`Python_NumPy_VERSION`

  The NumPy version.

## Hints

`Python_ROOT_DIR`

  Define the root directory of a Python installation.

`Python_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.

`Python_FIND_ABI`

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

  Note

  This hint will be honored only when searched for `Python` version 3.

  Note

  If `Python_FIND_ABI` is not defined, any ABI will be searched.

  The `Python_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 posibilties (`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 (Python_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 (Python_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 `Python_FIND_ABI` is defined, `Python` distributions from python.org will be found only if value for each flag is `OFF` or `ANY`.

`Python_FIND_STRATEGY`

  This variable defines how lookup will be done. The `Python_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`.

`Python_FIND_REGISTRY`

  On Windows the `Python_FIND_REGISTRY` variable determine the order of preference between registry and environment variables. the `Python_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.

`Python_FIND_FRAMEWORK`

  On macOS the `Python_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 `Python_FIND_FRAMEWORK` is not defined, `CMAKE_FIND_FRAMEWORK` variable will be used, if any.

`Python_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 `Python_FIND_REGISTRY` and `CMAKE_FIND_FRAMEWORK` variables. The `Python_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 `Python_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.

`Python_FIND_IMPLEMENTATIONS`

  This variable defines, in an ordered list, the different implementations which will be searched. The `Python_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 `Python_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:

`Python_EXECUTABLE`

  The path to the interpreter.

`Python_COMPILER`

  The path to the compiler.

`Python_DOTNET_LAUNCHER`

  The `.Net` interpreter. Only used by `IronPython` implementation.

`Python_LIBRARY`

  The path to the library. It will be used to compute the variables `Python_LIBRARIES`, `Python_LIBRAY_DIRS` and `Python_RUNTIME_LIBRARY_DIRS`.

`Python_INCLUDE_DIR`

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

`Python_NumPy_INCLUDE_DIR`

  The path to the directory of the `NumPy` headers. It will be used to compute the variable `Python_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 responsability 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 controled with the following variable:

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

    Python_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 `Python_SOABI` value, if any.