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diff --git a/doc/languages-frameworks/python.xml b/doc/languages-frameworks/python.xml new file mode 100644 index 00000000000..57aceeb4868 --- /dev/null +++ b/doc/languages-frameworks/python.xml @@ -0,0 +1,447 @@ +<section xmlns="http://docbook.org/ns/docbook" + xmlns:xlink="http://www.w3.org/1999/xlink" + xml:id="sec-python"> + +<title>Python</title> + +<para> + Currently supported interpreters are <varname>python26</varname>, <varname>python27</varname>, + <varname>python33</varname>, <varname>python34</varname>, <varname>python35</varname> + and <varname>pypy</varname>. +</para> + +<para> + <varname>python</varname> is an alias to <varname>python27</varname> and <varname>python3</varname> is an alias to <varname>python34</varname>. +</para> + +<para> + <varname>python26</varname> and <varname>python27</varname> do not include modules that require + external dependencies (to reduce dependency bloat). Following modules need to be added as + <varname>buildInput</varname> explicitly: +</para> + +<itemizedlist> + <listitem><para><varname>python.modules.bsddb</varname></para></listitem> + <listitem><para><varname>python.modules.curses</varname></para></listitem> + <listitem><para><varname>python.modules.curses_panel</varname></para></listitem> + <listitem><para><varname>python.modules.crypt</varname></para></listitem> + <listitem><para><varname>python.modules.gdbm</varname></para></listitem> + <listitem><para><varname>python.modules.sqlite3</varname></para></listitem> + <listitem><para><varname>python.modules.tkinter</varname></para></listitem> + <listitem><para><varname>python.modules.readline</varname></para></listitem> +</itemizedlist> + +<para>For convenience <varname>python27Full</varname> and <varname>python26Full</varname> +are provided with all modules included.</para> + +<para> + Python packages that + use <link xlink:href="http://pypi.python.org/pypi/setuptools/"><literal>setuptools</literal></link> or <literal>distutils</literal>, + can be built using the <varname>buildPythonPackage</varname> function as documented below. +</para> + +<para> + All packages depending on any Python interpreter get appended <varname>$out/${python.sitePackages}</varname> + to <literal>$PYTHONPATH</literal> if such directory exists. +</para> + +<variablelist> + <title> + Useful attributes on interpreters packages: + </title> + + <varlistentry> + <term><varname>libPrefix</varname></term> + <listitem><para> + Name of the folder in <literal>${python}/lib/</literal> for corresponding interpreter. + </para></listitem> + </varlistentry> + + <varlistentry> + <term><varname>interpreter</varname></term> + <listitem><para> + Alias for <literal>${python}/bin/${executable}.</literal> + </para></listitem> + </varlistentry> + + <varlistentry> + <term><varname>buildEnv</varname></term> + <listitem><para> + Function to build python interpreter environments with extra packages bundled together. + See <xref linkend="ssec-python-build-env" /> for usage and documentation. + </para></listitem> + </varlistentry> + + <varlistentry> + <term><varname>sitePackages</varname></term> + <listitem><para> + Alias for <literal>lib/${libPrefix}/site-packages</literal>. + </para></listitem> + </varlistentry> + + <varlistentry> + <term><varname>executable</varname></term> + <listitem><para> + Name of the interpreter executable, ie <literal>python3.4</literal>. + </para></listitem> + </varlistentry> + +</variablelist> +<section xml:id="ssec-build-python-package"><title><varname>buildPythonPackage</varname> function</title> + + <para> + The function is implemented in <link xlink:href="https://github.com/NixOS/nixpkgs/blob/master/pkgs/development/python-modules/generic/default.nix"> + <filename>pkgs/development/python-modules/generic/default.nix</filename></link>. + Example usage: + +<programlisting language="nix"> +twisted = buildPythonPackage { + name = "twisted-8.1.0"; + + src = pkgs.fetchurl { + url = http://tmrc.mit.edu/mirror/twisted/Twisted/8.1/Twisted-8.1.0.tar.bz2; + sha256 = "0q25zbr4xzknaghha72mq57kh53qw1bf8csgp63pm9sfi72qhirl"; + }; + + propagatedBuildInputs = [ self.ZopeInterface ]; + + meta = { + homepage = http://twistedmatrix.com/; + description = "Twisted, an event-driven networking engine written in Python"; + license = stdenv.lib.licenses.mit; + }; +}; +</programlisting> + + Most of Python packages that use <varname>buildPythonPackage</varname> are defined + in <link xlink:href="https://github.com/NixOS/nixpkgs/blob/master/pkgs/top-level/python-packages.nix"><filename>pkgs/top-level/python-packages.nix</filename></link> + and generated for each python interpreter separately into attribute sets <varname>python26Packages</varname>, + <varname>python27Packages</varname>, <varname>python35Packages</varname>, <varname>python33Packages</varname>, + <varname>python34Packages</varname> and <varname>pypyPackages</varname>. + </para> + + <para> + <function>buildPythonPackage</function> mainly does four things: + + <orderedlist> + <listitem><para> + In the <varname>buildPhase</varname>, it calls + <literal>${python.interpreter} setup.py bdist_wheel</literal> to build a wheel binary zipfile. + </para></listitem> + + <listitem><para> + In the <varname>installPhase</varname>, it installs the wheel file using + <literal>pip install *.whl</literal>. + </para></listitem> + + <listitem><para> + In the <varname>postFixup</varname> phase, <literal>wrapPythonPrograms</literal> + bash function is called to wrap all programs in <filename>$out/bin/*</filename> + directory to include <literal>$PYTHONPATH</literal> and <literal>$PATH</literal> + environment variables. + </para></listitem> + + <listitem><para> + In the <varname>installCheck</varname> phase, <literal>${python.interpreter} setup.py test</literal> + is ran. + </para></listitem> + </orderedlist> + </para> + + <para>By default <varname>doCheck = true</varname> is set</para> + + <para> + As in Perl, dependencies on other Python packages can be specified in the + <varname>buildInputs</varname> and + <varname>propagatedBuildInputs</varname> attributes. If something is + exclusively a build-time dependency, use + <varname>buildInputs</varname>; if it’s (also) a runtime dependency, + use <varname>propagatedBuildInputs</varname>. + </para> + + <para> + By default <varname>meta.platforms</varname> is set to the same value + as the interpreter unless overriden otherwise. + </para> + + <variablelist> + <title> + <varname>buildPythonPackage</varname> parameters + (all parameters from <varname>mkDerivation</varname> function are still supported) + </title> + + <varlistentry> + <term><varname>namePrefix</varname></term> + <listitem><para> + Prepended text to <varname>${name}</varname> parameter. + Defaults to <literal>"python3.3-"</literal> for Python 3.3, etc. Set it to + <literal>""</literal> + if you're packaging an application or a command line tool. + </para></listitem> + </varlistentry> + + <varlistentry> + <term><varname>disabled</varname></term> + <listitem><para> + If <varname>true</varname>, package is not build for + particular python interpreter version. Grep around + <filename>pkgs/top-level/python-packages.nix</filename> + for examples. + </para></listitem> + </varlistentry> + + <varlistentry> + <term><varname>setupPyBuildFlags</varname></term> + <listitem><para> + List of flags passed to <command>setup.py build_ext</command> command. + </para></listitem> + </varlistentry> + + <varlistentry> + <term><varname>pythonPath</varname></term> + <listitem><para> + List of packages to be added into <literal>$PYTHONPATH</literal>. + Packages in <varname>pythonPath</varname> are not propagated + (contrary to <varname>propagatedBuildInputs</varname>). + </para></listitem> + </varlistentry> + + <varlistentry> + <term><varname>preShellHook</varname></term> + <listitem><para> + Hook to execute commands before <varname>shellHook</varname>. + </para></listitem> + </varlistentry> + + <varlistentry> + <term><varname>postShellHook</varname></term> + <listitem><para> + Hook to execute commands after <varname>shellHook</varname>. + </para></listitem> + </varlistentry> + + <varlistentry> + <term><varname>makeWrapperArgs</varname></term> + <listitem><para> + A list of strings. Arguments to be passed to + <varname>makeWrapper</varname>, which wraps generated binaries. By + default, the arguments to <varname>makeWrapper</varname> set + <varname>PATH</varname> and <varname>PYTHONPATH</varname> environment + variables before calling the binary. Additional arguments here can + allow a developer to set environment variables which will be + available when the binary is run. For example, + <varname>makeWrapperArgs = ["--set FOO BAR" "--set BAZ QUX"]</varname>. + </para></listitem> + </varlistentry> + + </variablelist> + +</section> + +<section xml:id="ssec-python-build-env"><title><function>python.buildEnv</function> function</title> + <para> + Create Python environments using low-level <function>pkgs.buildEnv</function> function. Example <filename>default.nix</filename>: + +<programlisting language="nix"> +<![CDATA[with import <nixpkgs> {}; + +python.buildEnv.override { + extraLibs = [ pkgs.pythonPackages.pyramid ]; + ignoreCollisions = true; +}]]> +</programlisting> + + Running <command>nix-build</command> will create + <filename>/nix/store/cf1xhjwzmdki7fasgr4kz6di72ykicl5-python-2.7.8-env</filename> + with wrapped binaries in <filename>bin/</filename>. + </para> + + <para> + You can also use <varname>env</varname> attribute to create local + environments with needed packages installed (somewhat comparable to + <literal>virtualenv</literal>). For example, with the following + <filename>shell.nix</filename>: + +<programlisting language="nix"> +<![CDATA[with import <nixpkgs> {}; + +(python3.buildEnv.override { + extraLibs = with python3Packages; + [ numpy + requests + ]; +}).env]]> +</programlisting> + + Running <command>nix-shell</command> will drop you into a shell where + <command>python</command> will have specified packages in its path. + </para> + + <variablelist> + <title> + <function>python.buildEnv</function> arguments + </title> + + <varlistentry> + <term><varname>extraLibs</varname></term> + <listitem><para> + List of packages installed inside the environment. + </para></listitem> + </varlistentry> + + <varlistentry> + <term><varname>postBuild</varname></term> + <listitem><para> + Shell command executed after the build of environment. + </para></listitem> + </varlistentry> + + <varlistentry> + <term><varname>ignoreCollisions</varname></term> + <listitem><para> + Ignore file collisions inside the environment (default is <varname>false</varname>). + </para></listitem> + </varlistentry> + </variablelist> +</section> + +<section xml:id="ssec-python-tools"><title>Tools</title> + +<para>Packages inside nixpkgs are written by hand. However many tools +exist in community to help save time. No tool is preferred at the moment. +</para> + +<itemizedlist> + + <listitem><para> + <link xlink:href="https://github.com/proger/python2nix">python2nix</link> + by Vladimir Kirillov + </para></listitem> + + <listitem><para> + <link xlink:href="https://github.com/garbas/pypi2nix">pypi2nix</link> + by Rok Garbas + </para></listitem> + + <listitem><para> + <link xlink:href="https://github.com/offlinehacker/pypi2nix">pypi2nix</link> + by Jaka Hudoklin + </para></listitem> + +</itemizedlist> + +</section> + +<section xml:id="ssec-python-development"><title>Development</title> + + <para> + To develop Python packages <function>buildPythonPackage</function> has + additional logic inside <varname>shellPhase</varname> to run + <command>pip install -e . --prefix $TMPDIR/</command> for the package. + </para> + + <warning><para><varname>shellPhase</varname> is executed only if <filename>setup.py</filename> + exists.</para></warning> + + <para> + Given a <filename>default.nix</filename>: + +<programlisting language="nix"> +<![CDATA[with import <nixpkgs> {}; + +buildPythonPackage { + name = "myproject"; + + buildInputs = with pkgs.pythonPackages; [ pyramid ]; + + src = ./.; +}]]> +</programlisting> + + Running <command>nix-shell</command> with no arguments should give you + the environment in which the package would be build with + <command>nix-build</command>. + </para> + + <para> + Shortcut to setup environments with C headers/libraries and python packages: + + <programlisting language="bash">$ nix-shell -p pythonPackages.pyramid zlib libjpeg git</programlisting> + </para> + + <note><para> + There is a boolean value <varname>lib.inNixShell</varname> set to + <varname>true</varname> if nix-shell is invoked. + </para></note> + +</section> + +<section xml:id="ssec-python-faq"><title>FAQ</title> + +<variablelist> + + <varlistentry> + <term>How to solve circular dependencies?</term> + <listitem><para> + If you have packages <varname>A</varname> and <varname>B</varname> that + depend on each other, when packaging <varname>B</varname> override package + <varname>A</varname> not to depend on <varname>B</varname> as input + (and also the other way around). + </para></listitem> + </varlistentry> + + <varlistentry> + <term><varname>install_data / data_files</varname> problems resulting into <literal>error: could not create '/nix/store/6l1bvljpy8gazlsw2aw9skwwp4pmvyxw-python-2.7.8/etc': Permission denied</literal></term> + <listitem><para> + <link xlink:href="https://bitbucket.org/pypa/setuptools/issue/130/install_data-doesnt-respect-prefix"> + Known bug in setuptools <varname>install_data</varname> does not respect --prefix</link>. Example of + such package using the feature is <filename>pkgs/tools/X11/xpra/default.nix</filename>. As workaround + install it as an extra <varname>preInstall</varname> step: + + <programlisting>${python.interpreter} setup.py install_data --install-dir=$out --root=$out +sed -i '/ = data_files/d' setup.py</programlisting> + </para></listitem> + </varlistentry> + + <varlistentry> + <term>Rationale of non-existent global site-packages</term> + <listitem><para> + There is no need to have global site-packages in Nix. Each package has isolated + dependency tree and installing any python package will only populate <varname>$PATH</varname> + inside user environment. See <xref linkend="ssec-python-build-env" /> to create self-contained + interpreter with a set of packages. + </para></listitem> + </varlistentry> + +</variablelist> + +</section> + + +<section xml:id="ssec-python-contrib"><title>Contributing guidelines</title> +<para> + Following rules are desired to be respected: +</para> + +<itemizedlist> + + <listitem><para> + Make sure package builds for all python interpreters. Use <varname>disabled</varname> argument to + <function>buildPythonPackage</function> to set unsupported interpreters. + </para></listitem> + + <listitem><para> + If tests need to be disabled for a package, make sure you leave a comment about reasoning. + </para></listitem> + + <listitem><para> + Packages in <link xlink:href="https://github.com/NixOS/nixpkgs/blob/master/pkgs/top-level/python-packages.nix"><filename>pkgs/top-level/python-packages.nix</filename></link> + are sorted quasi-alphabetically to avoid merge conflicts. + </para></listitem> + +</itemizedlist> + +</section> + +</section> + |