2.Using Python on Unix platforms

2.1.Getting and installing the latest version of Python

2.1.1.On Linux

Python comes preinstalled on most Linux distributions, and is available as apackage on all others. However there are certain features you might want to usethat are not available on your distro’s package. You can easily compile thelatest version of Python from source.

In the event that Python doesn’t come preinstalled and isn’t in the repositories aswell, you can easily make packages for your own distro. Have a look at thefollowing links:

2.1.2.On FreeBSD and OpenBSD

  • FreeBSD users, to add the package use:

    pkginstallpython3

  • OpenBSD users, to add the package use:

    pkg_add-rpythonpkg_addftp://ftp.openbsd.org/pub/OpenBSD/4.2/packages/<insertyourarchitecturehere>/python-<version>.tgz

    For example i386 users get the 2.5.1 version of Python using:

    pkg_addftp://ftp.openbsd.org/pub/OpenBSD/4.2/packages/i386/python-2.5.1p2.tgz

2.1.3.On OpenSolaris

You can get Python fromOpenCSW. Various versionsof Python are available and can be installed with e.g.pkgutil-ipython27.

2.2.Building Python

If you want to compile CPython yourself, first thing you should do is get thesource. You can download either thelatest release’s source or just grab a freshclone. (If you wantto contribute patches, you will need a clone.)

The build process consists of the usual commands:

./configuremakemakeinstall

Configuration options and caveats for specific Unixplatforms are extensively documented in theREADME.rst file in theroot of the Python source tree.

Warning

makeinstall can overwrite or masquerade thepython3 binary.makealtinstall is therefore recommended instead ofmakeinstallsince it only installsexec_prefix/bin/pythonversion.

2.3.Python-related paths and files

These are subject to difference depending on local installation conventions;prefix andexec_prefixare installation-dependent and should be interpreted as for GNU software; theymay be the same.

For example, on most Linux systems, the default for both is/usr.

File/directory

Meaning

exec_prefix/bin/python3

Recommended location of the interpreter.

prefix/lib/pythonversion,exec_prefix/lib/pythonversion

Recommended locations of the directoriescontaining the standard modules.

prefix/include/pythonversion,exec_prefix/include/pythonversion

Recommended locations of the directoriescontaining the include files needed fordeveloping Python extensions andembedding the interpreter.

2.4.Miscellaneous

To easily use Python scripts on Unix, you need to make them executable,e.g. with

$chmod+xscript

and put an appropriate Shebang line at the top of the script. A good choice isusually

#!/usr/bin/env python3

which searches for the Python interpreter in the wholePATH. However,some Unices may not have theenv command, so you may need to hardcode/usr/bin/python3 as the interpreter path.

To use shell commands in your Python scripts, look at thesubprocess module.

2.5.Custom OpenSSL

  1. To use your vendor’s OpenSSL configuration and system trust store, locatethe directory withopenssl.cnf file or symlink in/etc. On mostdistribution the file is either in/etc/ssl or/etc/pki/tls. Thedirectory should also contain acert.pem file and/or acertsdirectory.

    $find/etc/-nameopenssl.cnf-printf"%h\n"/etc/ssl

  2. Download, build, and install OpenSSL. Make sure you useinstall_sw andnotinstall. Theinstall_sw target does not overrideopenssl.cnf.

    $curl-Ohttps://www.openssl.org/source/openssl-VERSION.tar.gz$tarxzfopenssl-VERSION$pushdopenssl-VERSION$./config\--prefix=/usr/local/custom-openssl\--libdir=lib\--openssldir=/etc/ssl$make-j1depend$make-j8$makeinstall_sw$popd

  3. Build Python with custom OpenSSL(see the configure--with-openssl and--with-openssl-rpath options)

    $pushdpython-3.x.x$./configure-C\--with-openssl=/usr/local/custom-openssl\--with-openssl-rpath=auto\--prefix=/usr/local/python-3.x.x$make-j8$makealtinstall

Note

Patch releases of OpenSSL have a backwards compatible ABI. You don’t needto recompile Python to update OpenSSL. It’s sufficient to replace thecustom OpenSSL installation with a newer version.