# FindPython

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

Three 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).
- `NumPy`: search for NumPy include directories.

If no `COMPONENTS` is specified, `Interpreter` is assumed.

To ensure consistent versions between components `Interpreter`, `Compiler`, `Development` 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` 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::Python`
  Python library for Python embedding. Target defined if component `Development` is found.
`Python::Module`
  Python library for Python module. Target defined if component `Development` 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
`Python_STDLIB`

  Standard platform independent installation directory.

  Information returned by `distutils.sysconfig.get_python_lib(plat_specific=False,standard_lib=True)`.

`Python_STDARCH`

  Standard platform dependent installation directory.

  Information returned by `distutils.sysconfig.get_python_lib(plat_specific=True,standard_lib=True)`.

`Python_SITELIB`

  Third-party platform independent installation directory.

  Information returned by `distutils.sysconfig.get_python_lib(plat_specific=False,standard_lib=False)`.

`Python_SITEARCH`

  Third-party platform dependent installation directory.

  Information returned by `distutils.sysconfig.get_python_lib(plat_specific=True,standard_lib=False)`.

`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_Development_FOUND`
  System has the Python development artifacts.
`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_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 empty or 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 empty or 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 be set to empty or 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. It is meaningfull 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 empty or 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. 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.

## 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_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.

## 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 (my_module MODULE src1.cpp)

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