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| PEP: 250 | |
| Title: Using site-packages on Windows | |
| Version: $Revision$ | |
| Last-Modified: $Date$ | |
| Author: p.f.moore@gmail.com (Paul Moore) | |
| Status: Final | |
| Type: Standards Track | |
| Content-Type: text/x-rst | |
| Created: 30-Mar-2001 | |
| Python-Version: 2.2 | |
| Post-History: 30-Mar-2001 | |
| Abstract | |
| ======== | |
| The standard Python distribution includes a directory | |
| ``Lib/site-packages``, which is used on Unix platforms to hold | |
| locally installed modules and packages. The ``site.py`` module | |
| distributed with Python includes support for locating other | |
| modules in the site-packages directory. | |
| This PEP proposes that the site-packages directory should be used | |
| on the Windows platform in a similar manner. | |
| Motivation | |
| ========== | |
| On Windows platforms, the default setting for ``sys.path`` does not | |
| include a directory suitable for users to install locally | |
| developed modules. The "expected" location appears to be the | |
| directory containing the Python executable itself. This is also | |
| the location where distutils (and distutils-generated installers) | |
| installs packages. Including locally developed code in the same | |
| directory as installed executables is not good practice. | |
| Clearly, users can manipulate ``sys.path``, either in a locally | |
| modified ``site.py``, or in a suitable ``sitecustomize.py``, or even via | |
| ``.pth`` files. However, there should be a standard location for such | |
| files, rather than relying on every individual site having to set | |
| their own policy. | |
| In addition, with distutils becoming more prevalent as a means of | |
| distributing modules, the need for a standard install location for | |
| distributed modules will become more common. It would be better | |
| to define such a standard now, rather than later when more | |
| distutils-based packages exist which will need rebuilding. | |
| It is relevant to note that prior to Python 2.1, the site-packages | |
| directory was not included in ``sys.path`` for Macintosh platforms. | |
| This has been changed in 2.1, and Macintosh includes ``sys.path`` now, | |
| leaving Windows as the only major platform with no site-specific | |
| modules directory. | |
| Implementation | |
| ============== | |
| The implementation of this feature is fairly trivial. All that | |
| would be required is a change to ``site.py``, to change the section | |
| setting sitedirs. The Python 2.1 version has:: | |
| if os.sep == '/': | |
| sitedirs = [makepath(prefix, | |
| "lib", | |
| "python" + sys.version[:3], | |
| "site-packages"), | |
| makepath(prefix, "lib", "site-python")] | |
| elif os.sep == ':': | |
| sitedirs = [makepath(prefix, "lib", "site-packages")] | |
| else: | |
| sitedirs = [prefix] | |
| A suitable change would be to simply replace the last 4 lines with:: | |
| else: | |
| sitedirs == [prefix, makepath(prefix, "lib", "site-packages")] | |
| Changes would also be required to distutils, to reflect this change | |
| in policy. A patch is available on Sourceforge, patch ID 445744, | |
| which implements this change. Note that the patch checks the Python | |
| version and only invokes the new behaviour for Python versions from | |
| 2.2 onwards. This is to ensure that distutils remains compatible | |
| with earlier versions of Python. | |
| Finally, the executable code which implements the Windows installer | |
| used by the ``bdist_wininst`` command will need changing to use the new | |
| location. A separate patch is available for this, currently | |
| maintained by Thomas Heller. | |
| Notes | |
| ===== | |
| - This change does not preclude packages using the current | |
| location -- the change only adds a directory to ``sys.path``, it | |
| does not remove anything. | |
| - Both the current location (``sys.prefix``) and the new directory | |
| (site-packages) are included in sitedirs, so that ``.pth`` files | |
| will be recognised in either location. | |
| - This proposal adds a single additional site-packages directory | |
| to sitedirs. On Unix platforms, two directories are added, one | |
| for version-independent files (Python code) and one for | |
| version-dependent code (C extensions). This is necessary on | |
| Unix, as the sitedirs include a common (across Python versions) | |
| package location, in ``/usr/local`` by default. As there is no such | |
| common location available on Windows, there is also no need for | |
| having two separate package directories. | |
| - If users want to keep DLLs in a single location on Windows, rather | |
| than keeping them in the package directory, the DLLs subdirectory | |
| of the Python install directory is already available for that | |
| purpose. Adding an extra directory solely for DLLs should not be | |
| necessary. | |
| Open Issues | |
| =========== | |
| - Comments from Unix users indicate that there may be issues with | |
| the current setup on the Unix platform. Rather than become | |
| involved in cross-platform issues, this PEP specifically limits | |
| itself to the Windows platform, leaving changes for other platforms | |
| to be covered in other PEPs. | |
| - There could be issues with applications which embed Python. To the | |
| author's knowledge, there should be no problem as a result of this | |
| change. There have been no comments (supportive or otherwise) from | |
| users who embed Python. | |
| Copyright | |
| ========= | |
| This document has been placed in the public domain. | |
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