6.15. Using Python

The Ports Collection supports parallel installation of multiple Python versions. Ports must use a correct python interpreter, according to the user-settable PYTHON_VERSION. Most prominently, this means replacing the path to python executable in scripts with the value of PYTHON_CMD.

Ports that install files under PYTHON_SITELIBDIR must use the pyXY- package name prefix, so their package name embeds the version of Python they are installed into.

PKGNAMEPREFIX=	${PYTHON_PKGNAMEPREFIX}
Table 6.19. Most Useful Variables for Ports That Use Python
USE_PYTHONThe port needs Python. Minimal required version can be specified with values such as 2.6+. Version ranges can also be specified, by separating two version numbers with a dash, for example, 2.6-2.7
USE_PYDISTUTILSUse Python distutils for configuring, compiling and installing. This is required when the port comes with setup.py. This overrides the do-build and do-install targets and may also override do-configure if GNU_CONFIGURE is not defined.
PYTHON_PKGNAMEPREFIXUsed as a PKGNAMEPREFIX to distinguish packages for different Python versions. Example: py24-
PYTHON_SITELIBDIRLocation of the site-packages tree, that contains installation path of Python (usually LOCALBASE). PYTHON_SITELIBDIR can be very useful when installing Python modules.
PYTHONPREFIX_SITELIBDIRThe PREFIX-clean variant of PYTHON_SITELIBDIR. Always use %%PYTHON_SITELIBDIR%% in pkg-plist when possible. The default value of %%PYTHON_SITELIBDIR%% is lib/python%%PYTHON_VERSION%%/site-packages
PYTHON_CMDPython interpreter command line, including version number.
PYNUMERICDependency line for numeric extension.
PYNUMPYDependency line for the new numeric extension, numpy. (PYNUMERIC is deprecated by upstream vendor).
PYXMLDependency line for XML extension (not needed for Python 2.0 and higher as it is also in base distribution).

A complete list of available variables can be found in /usr/ports/Mk/bsd.python.mk.

Some Python applications claim to have DESTDIR support (which would be required for staging) but it is broken (Mailman up to 2.1.16, for instance). This can be worked around by recompiling the scripts. This can be done, for example, in the post-build target. Assuming the Python scripts are supposed to reside in PYTHONPREFIX_SITELIBDIR after installation, this solution can be applied:

(cd ${STAGEDIR}${PREFIX} \
  && ${PYTHON_CMD} ${PYTHON_LIBDIR}/compileall.py \
   -d ${PREFIX} -f ${PYTHONPREFIX_SITELIBDIR:S;${PREFIX}/;;})

This recompiles the sources with a path relative to the stage directory, and prepends the value of PREFIX to the file name recorded in the byte-compiled output file by -d. -f is required to force recompilation, and the :S;${PREFIX}/;; strips prefixes from the value of PYTHONPREFIX_SITELIBDIR to make it relative to PREFIX.

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