PEP 250, Using site-packages on All Platforms, Paul Moore

pep-0250.txt

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+PEP: 250
+Title: Using site-packages on All Platforms
+Version $Revision$
+Author: gustav@morpheus.demon.co.uk (Paul Moore)
+Status: Draft
+Type: Standards Track
+Created: 2001-03-30
+Python-Version: 2.2
+Post-History:
+
+
+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
+    uniformly across all platforms for locally installed modules.
+
+
+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.  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 == [makepath(prefix, "lib", "site-packages")]
+
+    Changes would also be required to distutils, in the sysconfig.py
+    file.  It is worth noting that this file does not seem to have
+    been updated in line with the change of policy on the Macintosh,
+    as of this writing.
+
+
+Notes
+
+    1. It would be better if this change could be included in Python
+       2.1, as changing something of this nature is better done
+       sooner, rather than later, to reduce the backward-compatibility
+       burden. This is extremely unlikely to happen at this late stage
+       in the release cycle, however.
+
+    2. This change does not preclude packages using the current
+       location -- the change only adds a directory to sys.path, it
+       does not remove anything.
+
+    3. In the Windows distribution of Python 2.1 (beta 1), the
+       Lib\site-packages directory has been removed.  It would need to
+       be reinstated.
+
+
+Copyright
+
+    This document has been placed in the public domain.
+
+
+
+Local Variables:
+mode: indented-text
+indent-tabs-mode: nil
+End: