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diff --git a/Doc/distutils/configfile.rst b/Doc/distutils/configfile.rst new file mode 100644 index 0000000..0ccd5fd --- /dev/null +++ b/Doc/distutils/configfile.rst @@ -0,0 +1,130 @@ +.. _setup-config: + +************************************ +Writing the Setup Configuration File +************************************ + +Often, it's not possible to write down everything needed to build a distribution +*a priori*: you may need to get some information from the user, or from the +user's system, in order to proceed. As long as that information is fairly +simple---a list of directories to search for C header files or libraries, for +example---then providing a configuration file, :file:`setup.cfg`, for users to +edit is a cheap and easy way to solicit it. Configuration files also let you +provide default values for any command option, which the installer can then +override either on the command-line or by editing the config file. + +The setup configuration file is a useful middle-ground between the setup script +---which, ideally, would be opaque to installers [#]_---and the command-line to +the setup script, which is outside of your control and entirely up to the +installer. In fact, :file:`setup.cfg` (and any other Distutils configuration +files present on the target system) are processed after the contents of the +setup script, but before the command-line. This has several useful +consequences: + +.. % (If you have more advanced needs, such as determining which extensions +.. % to build based on what capabilities are present on the target system, +.. % then you need the Distutils ``auto-configuration'' facility. This +.. % started to appear in Distutils 0.9 but, as of this writing, isn't mature +.. % or stable enough yet for real-world use.) + +* installers can override some of what you put in :file:`setup.py` by editing + :file:`setup.cfg` + +* you can provide non-standard defaults for options that are not easily set in + :file:`setup.py` + +* installers can override anything in :file:`setup.cfg` using the command-line + options to :file:`setup.py` + +The basic syntax of the configuration file is simple:: + + [command] + option=value + ... + +where *command* is one of the Distutils commands (e.g. :command:`build_py`, +:command:`install`), and *option* is one of the options that command supports. +Any number of options can be supplied for each command, and any number of +command sections can be included in the file. Blank lines are ignored, as are +comments, which run from a ``'#'`` character until the end of the line. Long +option values can be split across multiple lines simply by indenting the +continuation lines. + +You can find out the list of options supported by a particular command with the +universal :option:`--help` option, e.g. :: + + > python setup.py --help build_ext + [...] + Options for 'build_ext' command: + --build-lib (-b) directory for compiled extension modules + --build-temp (-t) directory for temporary files (build by-products) + --inplace (-i) ignore build-lib and put compiled extensions into the + source directory alongside your pure Python modules + --include-dirs (-I) list of directories to search for header files + --define (-D) C preprocessor macros to define + --undef (-U) C preprocessor macros to undefine + --swig-opts list of SWIG command line options + [...] + +Note that an option spelled :option:`--foo-bar` on the command-line is spelled +:option:`foo_bar` in configuration files. + +For example, say you want your extensions to be built "in-place"---that is, you +have an extension :mod:`pkg.ext`, and you want the compiled extension file +(:file:`ext.so` on Unix, say) to be put in the same source directory as your +pure Python modules :mod:`pkg.mod1` and :mod:`pkg.mod2`. You can always use the +:option:`--inplace` option on the command-line to ensure this:: + + python setup.py build_ext --inplace + +But this requires that you always specify the :command:`build_ext` command +explicitly, and remember to provide :option:`--inplace`. An easier way is to +"set and forget" this option, by encoding it in :file:`setup.cfg`, the +configuration file for this distribution:: + + [build_ext] + inplace=1 + +This will affect all builds of this module distribution, whether or not you +explicitly specify :command:`build_ext`. If you include :file:`setup.cfg` in +your source distribution, it will also affect end-user builds---which is +probably a bad idea for this option, since always building extensions in-place +would break installation of the module distribution. In certain peculiar cases, +though, modules are built right in their installation directory, so this is +conceivably a useful ability. (Distributing extensions that expect to be built +in their installation directory is almost always a bad idea, though.) + +Another example: certain commands take a lot of options that don't change from +run to run; for example, :command:`bdist_rpm` needs to know everything required +to generate a "spec" file for creating an RPM distribution. Some of this +information comes from the setup script, and some is automatically generated by +the Distutils (such as the list of files installed). But some of it has to be +supplied as options to :command:`bdist_rpm`, which would be very tedious to do +on the command-line for every run. Hence, here is a snippet from the Distutils' +own :file:`setup.cfg`:: + + [bdist_rpm] + release = 1 + packager = Greg Ward <gward@python.net> + doc_files = CHANGES.txt + README.txt + USAGE.txt + doc/ + examples/ + +Note that the :option:`doc_files` option is simply a whitespace-separated string +split across multiple lines for readability. + + +.. seealso:: + + :ref:`inst-config-syntax` in "Installing Python Modules" + More information on the configuration files is available in the manual for + system administrators. + + +.. rubric:: Footnotes + +.. [#] This ideal probably won't be achieved until auto-configuration is fully + supported by the Distutils. + |