PEP 297 – Support for System Upgrades
- Support for System Upgrades
- mal at lemburg.com (Marc-André Lemburg)
- Standards Track
This PEP is rejected for failure to generate significant interest.
This PEP proposes strategies to allow the Python standard library to be upgraded in parts without having to reinstall the complete distribution or having to wait for a new patch level release.
Python currently does not allow overriding modules or packages in
the standard library per default. Even though this is possible by
PYTHONPATH environment variable (the paths defined in
this variable are prepended to the Python standard library path),
there is no standard way of achieving this without changing the
Since Python’s standard library is starting to host packages which are also available separately, e.g. the distutils, email and PyXML packages, which can also be installed independently of the Python distribution, it is desirable to have an option to upgrade these packages without having to wait for a new patch level release of the Python interpreter to bring along the changes.
On some occasions, it may also be desirable to update modules of the standard library without going through the whole Python release cycle, e.g. in order to provide hot-fixes for security problems.
This PEP proposes two different but not necessarily conflicting solutions:
- Adding a new standard search path to
$stdlibpath/system-packagesjust before the
$stdlibpathentry. This complements the already existing entry for site add-ons
$stdlibpath/site-packageswhich is appended to the
sys.pathat interpreter startup time.
To make use of this new standard location, distutils will need to grow support for installing certain packages in
$stdlibpath/system-packagesrather than the standard location for third-party packages
- Tweaking distutils to install directly into
$stdlibpathfor the system upgrades rather than into
The first solution has a few advantages over the second:
- upgrades can be easily identified (just look in
- upgrades can be de-installed without affecting the rest of the interpreter installation
- modules can be virtually removed from packages; this is due to the way Python imports packages: once it finds the top-level package directory it stay in this directory for all subsequent package submodule imports
- the approach has an overall much cleaner design than the hackish install on top of an existing installation approach
The only advantages of the second approach are that the Python interpreter does not have to changed and that it works with older Python versions.
Both solutions require changes to distutils. These changes can also be implemented by package authors, but it would be better to define a standard way of switching on the proposed behaviour.
Solution 1: Python 2.6 and up
Solution 2: all Python versions supported by distutils
This document has been placed in the public domain.
Last modified: 2017-11-11 19:28:55 GMT