FindPython2 — CMake 4.2.6 Documentation

# FindPython2

Added in version 3.12.

Finds Python 2 interpreter, compiler and development environment (include directories and libraries):

    find_package(Python2 [<version>] [COMPONENTS <components>...] [...])

Added in version 3.19: 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 2 interpreter

- `Compiler`: search for Python 2 compiler. Only offered by IronPython.

- `Development`: search for development artifacts (include directories and libraries).

  Added in version 3.18: This component includes two sub-components which can be specified independently:

  - `Development.Module`: search for artifacts for Python 2 module developments.

  - `Development.Embed`: search for artifacts for Python 2 embedding developments.

Added in version 3.14:

- `NumPy`: search for NumPy include directories. Specifying this component imply also the components `Interpreter` and `Development.Module`.

Changed in version 4.2: The component `Development.Module` is no longer implied when the policy `CMP0201` is set to `NEW`.

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

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

Changed in version 4.1: In a cross-compiling mode (i.e. the `CMAKE_CROSSCOMPILING` variable is defined to true), the following constraints, when the policy `CMP0190` is set to `NEW`, now apply to the requested components:

- `Interpreter` or `Compiler` alone: the host artifacts will be searched.

- `Interpreter` or `Compiler` with `Development` or any sub-component: The target artifacts will be searched. In this case, the `CMAKE_CROSSCOMPILING_EMULATOR` variable must be defined and will be used to execute the interpreter or the compiler.

When both host and target artifacts are needed, two different calls to the `find_package()` command should be done. The `Python_ARTIFACTS_PREFIX` variable can be helpful in this situation.

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 (Python2 COMPONENTS Interpreter Development)

This module looks only for version 2 of Python. This module can be used concurrently with `FindPython3` 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 provides the following Imported Targets:

Changed in version 3.14: Imported Targets are only created when `CMAKE_ROLE` is `PROJECT`.

`Python2::Interpreter`

  Python 2 interpreter. This target is defined only if the `Interpreter` component is found.

`Python2::InterpreterDebug`

  Added in version 3.30.

  Python 2 debug interpreter. This target is defined only if the `Interpreter` component is found and the `Python2_EXECUTABLE_DEBUG` variable is defined. The target is only defined on the `Windows` platform.

`Python2::InterpreterMultiConfig`

  Added in version 3.30.

  Python 2 interpreter. The release or debug version of the interpreter will be used, based on the context (platform, configuration). This target is defined only if the `Interpreter` component is found

`Python2::Compiler`

  Python 2 compiler. This target is defined only if the `Compiler` component is found.

`Python2::Module`

  Added in version 3.15.

  Python 2 library for Python module. Target defined if component `Development.Module` is found.

`Python2::Python`

  Python 2 library for Python embedding. Target defined if component `Development.Embed` is found.

`Python2::NumPy`

  Added in version 3.14.

  NumPy library for Python 2. Target defined if component `NumPy` is found. Moreover, this target has the `Python2::Module` target as dependency.

  Changed in version 4.2: This target does not have anymore the `Python2::Module` target as dependency when the policy `CMP0201` is set to `NEW`.

## Result Variables

This module defines the following variables (see Standard Variable Names):

`Python2_FOUND`

  Boolean indicating whether system has the Python 2 requested components.

`Python2_Interpreter_FOUND`

  Boolean indicating whether system has the Python 2 interpreter.

`Python2_EXECUTABLE`

  Path to the Python 2 interpreter.

`Python2_EXECUTABLE_DEBUG`

  Added in version 3.30.

  Path to the debug Python 2 interpreter. It is only defined on the `Windows` platform.

`Python2_INTERPRETER`

  Added in version 3.30.

  Path to the Python 2 interpreter, defined as a `generator expression` selecting the `Python2_EXECUTABLE` or `Python2_EXECUTABLE_DEBUG` variable based on the context (platform, configuration).

`Python2_INTERPRETER_ID`
  A short string unique to the interpreter. Possible values include:

    - Python

    - ActivePython

    - Anaconda

    - Canopy

    - IronPython

    - PyPy

`Python2_STDLIB`

  Standard platform independent installation directory.

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

`Python2_STDARCH`

  Standard platform dependent installation directory.

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

`Python2_SITELIB`

  Third-party platform independent installation directory.

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

`Python2_SITEARCH`

  Third-party platform dependent installation directory.

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

`Python2_Compiler_FOUND`

  Boolean indicating whether system has the Python 2 compiler.

`Python2_COMPILER`

  Path to the Python 2 compiler. Only offered by IronPython.

`Python2_COMPILER_ID`
  A short string unique to the compiler. Possible values include:

    - IronPython

`Python2_DOTNET_LAUNCHER`

  Added in version 3.18.

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

`Python2_Development_FOUND`

  Boolean indicating whether system has the Python 2 development artifacts.

`Python2_Development.Module_FOUND`

  Added in version 3.18.

  Boolean indicating whether system has the Python 2 development artifacts for Python module.

`Python2_Development.Embed_FOUND`

  Added in version 3.18.

  Boolean indicating whether system has the Python 2 development artifacts for Python embedding.

`Python2_INCLUDE_DIRS`

  The Python 2 include directories.

`Python2_DEBUG_POSTFIX`

  Added in version 3.30.

  Postfix of debug python module. This variable can be used to define the `DEBUG_POSTFIX` target property.

`Python2_LINK_OPTIONS`

  Added in version 3.19.

  The Python 2 link options. Some configurations require specific link options for a correct build and execution.

`Python2_LIBRARIES`

  The Python 2 libraries.

`Python2_LIBRARY_DIRS`

  The Python 2 library directories.

`Python2_RUNTIME_LIBRARY_DIRS`

  The Python 2 runtime library directories.

`Python2_VERSION`

  Python 2 version.

`Python2_VERSION_MAJOR`

  Python 2 major version.

`Python2_VERSION_MINOR`

  Python 2 minor version.

`Python2_VERSION_PATCH`

  Python 2 patch version.

`Python2_PyPy_VERSION`

  Added in version 3.18.

  Python 2 PyPy version.

`Python2_NumPy_FOUND`

  Added in version 3.14.

  Boolean indicating whether system has the NumPy.

`Python2_NumPy_INCLUDE_DIRS`

  Added in version 3.14.

  The NumPy include directories.

`Python2_NumPy_VERSION`

  Added in version 3.14.

  The NumPy version.

## Hints

`Python2_ROOT_DIR`

  Define the root directory of a Python 2 installation.

`Python2_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.

  Note

  This hint will be ignored on `Windows` because static libraries are not available on this platform.

`Python2_FIND_STRATEGY`

  Added in version 3.15.

  This variable defines how lookup will be done. The `Python2_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`.

  See also `Python2_FIND_UNVERSIONED_NAMES`.

`Python2_FIND_REGISTRY`

  Added in version 3.13.

  On Windows the `Python2_FIND_REGISTRY` variable determine the order of preference between registry and environment variables. the `Python2_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.

`Python2_FIND_FRAMEWORK`

  Added in version 3.15.

  On macOS the `Python2_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 `Python2_FIND_FRAMEWORK` is not defined, `CMAKE_FIND_FRAMEWORK` variable will be used, if any.

`Python2_FIND_VIRTUALENV`

  Added in version 3.15.

  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 `Python2_FIND_REGISTRY` and `CMAKE_FIND_FRAMEWORK` variables. The `Python2_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 `Python2_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.

  Added in version 3.17: Added support for `conda` environments.

  Note

  If the component `Development` is requested (or one of its sub-components) and is not found or the wrong artifacts are returned, including also the component `Interpreter` may be helpful.

`Python2_FIND_IMPLEMENTATIONS`

  Added in version 3.18.

  This variable defines, in an ordered list, the different implementations which will be searched. The `Python2_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 `Python2_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.

`Python2_FIND_UNVERSIONED_NAMES`

  Added in version 3.20.

  This variable defines how the generic names will be searched. Currently, it only applies to the generic names of the interpreter, namely, `python2` and `python`. The `Python2_FIND_UNVERSIONED_NAMES` variable can be set to one of the following values:

  - `FIRST`: The generic names are searched before the more specialized ones (such as `python2.5` for example).

  - `LAST`: The generic names are searched after the more specialized ones. This is the default.

  - `NEVER`: The generic name are not searched at all.

  See also `Python2_FIND_STRATEGY`.

## Artifacts Specification

Added in version 3.16.

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

`Python2_EXECUTABLE`

  The path to the interpreter.

`Python2_COMPILER`

  The path to the compiler.

`Python2_DOTNET_LAUNCHER`

  Added in version 3.18.

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

`Python2_LIBRARY`

  The path to the library. It will be used to compute the variables `Python2_LIBRARIES`, `Python2_LIBRARY_DIRS` and `Python2_RUNTIME_LIBRARY_DIRS`.

`Python2_INCLUDE_DIR`

  The path to the directory of the `Python` headers. It will be used to compute the variable `Python2_INCLUDE_DIRS`.

`Python2_NumPy_INCLUDE_DIR`

  The path to the directory of the `NumPy` headers. It will be used to compute the variable `Python2_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:

`Python2_ARTIFACTS_INTERACTIVE`

  Added in version 3.18.

  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.

`Python2_ARTIFACTS_PREFIX`

  Added in version 4.0.

  Define a custom prefix which will be used for the definition of all the result variables, targets, and commands. By using this variable, this module supports multiple calls in the same directory with different version/component requirements. For example, in case of cross-compilation, development components are needed but the native python interpreter can also be required:

      find_package(Python2 COMPONENTS Development)

      set(Python2_ARTIFACTS_PREFIX "_HOST")
      find_package(Python2 COMPONENTS Interpreter)

      # Here Python2_HOST_EXECUTABLE and Python2_HOST::Interpreter artifacts are defined

  Note

  For consistency with standard behavior of modules, the various standard `_FOUND` variables (i.e. without the custom prefix) are also defined by each call to the `find_package()` command.

## Commands

This module defines the command `Python2_add_library` (when `CMAKE_ROLE` is `PROJECT`), which has the same semantics as `add_library()` and adds a dependency to target `Python2::Python` or, when library type is `MODULE`, to target `Python2::Module` and takes care of Python module naming rules:

    Python2_add_library (<name> [STATIC | SHARED | MODULE]
                         <source1> [<source2> ...])

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

Added in version 3.30: For `MODULE` type, the `DEBUG_POSTFIX` target property is initialized with the value of `Python2_DEBUG_POSTFIX` variable if defined.