130 lines
4.7 KiB
Plaintext
130 lines
4.7 KiB
Plaintext
PEP: 250
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Title: Using site-packages on All Platforms
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Version $Revision$
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Author: gustav@morpheus.demon.co.uk (Paul Moore)
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Status: Draft
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Type: Standards Track
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Created: 2001-03-30
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Python-Version: 2.2
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Post-History: 30-Mar-2001
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Abstract
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The standard Python distribution includes a directory
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Lib/site-packages, which is used on Unix platforms to hold
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locally-installed modules and packages. The site.py module
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distributed with Python includes support for locating other
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modules in the site-packages directory.
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This PEP proposes that the site-packages directory should be used
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uniformly across all platforms for locally installed modules.
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Motivation
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On Windows platforms, the default setting for sys.path does not
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include a directory suitable for users to install locally
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developed modules. The "expected" location appears to be the
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directory containing the Python executable itself. Including
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locally developed code in the same directory as installed
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executables is not good practice.
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Clearly, users can manipulate sys.path, either in a locally
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modified site.py, or in a suitable sitecustomize.py, or even via
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.pth files. However, there should be a standard location for such
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files, rather than relying on every individual site having to set
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their own policy.
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In addition, with distutils becoming more prevalent as a means of
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distributing modules, the need for a standard install location for
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distributed modules will become more common. It would be better
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to define such a standard now, rather than later when more
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distutils-based packages exist which will need rebuilding.
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It is relevant to note that prior to Python 2.1, the site-packages
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directory was not included in sys.path for Macintosh platforms.
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This has been changed in 2.1, and Macintosh includes sys.path now,
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leaving Windows as the only major platform with no site-specific
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modules directory.
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Implementation
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The implementation of this feature is fairly trivial. All that
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would be required is a change to site.py, to change the section
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setting sitedirs. The Python 2.1 version has
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if os.sep == '/':
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sitedirs = [makepath(prefix,
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"lib",
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"python" + sys.version[:3],
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"site-packages"),
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makepath(prefix, "lib", "site-python")]
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elif os.sep == ':':
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sitedirs = [makepath(prefix, "lib", "site-packages")]
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else:
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sitedirs = [prefix]
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A suitable change would be to simply replace the last 4 lines with
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else:
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sitedirs == [prefix, makepath(prefix, "lib", "site-packages")]
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Changes would also be required to distutils, in the sysconfig.py
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file. It is worth noting that this file does not seem to have
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been updated in line with the change of policy on the Macintosh,
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as of this writing.
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Notes
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- This change does not preclude packages using the current
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location -- the change only adds a directory to sys.path, it
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does not remove anything.
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- Both the current location (sys.prefix) and the new directory
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(site-packages) are included in sitedirs, so that .pth files
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will be recognized in either location.
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- This proposal adds a single additional site-packages directory
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to sitedirs. On Unix platforms, two directories are added, one
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for version-independent files (Python code) and one for
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version-dependent code (C extensions). This is necessary on
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Unix, as the sitedirs include a common (across Python versions)
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package location, in /usr/local by default. As there is no such
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common location available on Windows, there is also no need for
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having two separate package directories.
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- If users want to keep DLLs in a single location on Windows,
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rather than keeping them in the package directory, the DLLs
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subdirectory of the Python install directory is available for
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that purpose. Adding an extra directory solely for DLLs should
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not be necessary.
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Open Issues
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- There have been no comments on this proposal from non-Windows
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users. In the absence of such comments, it is assumed that there
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will be no adverse effects on such platforms caused by the
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proposed change. (The author knows of no reason why there should
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be).
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- There could be issues with applications which embed Python. To
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the author's knowledge, there should be no problem as a result
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of this change. Again, there have been no comments (supportive
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or otherwise) from users who embed Python.
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Copyright
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This document has been placed in the public domain.
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End:
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