PEP: 262 Title: A Database of Installed Python Packages Version: $Revision$ Author: A.M. Kuchling Type: Standards Track Created: 08-Jul-2001 Status: Draft Post-History: Introduction This PEP describes a format for a database of Python packages installed on a system. Requirements We need a way to figure out what packages, and what versions of those packages, are installed on a system. We want to provide features similar to CPAN, APT, or RPM. Required use cases that should be supported are: * Is package X on a system? * What version of package X is installed? * Where can the new version of package X be found? XXX Does this mean "a home page where the user can go and find a download link", or "a place where a program can find the newest version?" Perhaps both... * What files did package X put on my system? * What package did the file x/y/z.py come from? * Has anyone modified x/y/z.py locally? Database Location The database lives in a bunch of files under /lib/python/install/. This location will be called INSTALLDB through the remainder of this PEP. XXX is that a good location? What effect does platform-dependent code vs. platform-independent code have on this? The structure of the database is deliberately kept simple; each file in this directory or its subdirectories (if any) describes a single package. The rationale for scanning subdirectories is that we can move to a directory-based indexing scheme if the package directory contains too many entries. That is, instead of INSTALLDB/Numeric, we could switch to INSTALLDB/N/Nu/Numeric or some similar scheme. XXX how much do we care about performance? Do we really need to use an anydbm file or something similar? XXX is the actual filename important? Let's say the installation data for PIL is in the file INSTALLDB/Numeric. Is this OK? When we want to figure out if Numeric is installed, do we want to open a single file, or have to scan them all? Note that for human-interface purposes, we'll often have to scan all the packages anyway, for a case-insensitive or keyword search. Database Contents Each file in INSTALLDB or its subdirectories describes a single package, and has the following contents: An initial line listing the sections in this file, separated by whitespace. Currently this will always be 'PKG-INFO FILES'. This is for future-proofing; if we add a new section, for example to list documentation files, then we'd add a DOCS section and list it in the contents. Sections are always separated by blank lines. XXX too simple? [PKG-INFO section] An initial set of RFC-822 headers containing the package information for a file, as described in PEP 241, "Metadata for Python Software Packages". A blank line indicating the end of the PKG-INFO section. An entry for each file installed by the package. XXX Are .pyc and .pyo files in this list? What about compiled .so files? AMK thinks "no" and "yes", respectively. Each file's entry is a single tab-delimited line that contains the following fields: XXX should each file entry be all on one line and tab-delimited? More RFC-822 headers? AMK thinks tab-delimited seems sufficent. * The file's size * XXX do we need to store permissions? The owner/group? * An MD5 digest of the file, written in hex. (XXX All 16 bytes of the digest seems unnecessary; first 8 bytes only, maybe? Is a zlib.crc32() hash sufficient?) * The file's full path, as installed on the system. (XXX should it be relative to sys.prefix, or sys.prefix + '/lib/python?' If so, full paths are still needed; consider a package that installs a startup script such as /etc/init.d/zope) * XXX some sort of type indicator, to indicate whether this is a Python module, binary module, documentation file, config file? Do we need this? A package that uses the Distutils for installation will automatically update the database. Packages that roll their own installation XXX what's the relationship between this database and the RPM or DPKG database? I'm tempted to make the Python database completely optional; a distributor can preserve the interface of the package management tool and replace it with their own wrapper on top of their own package manager. (XXX but how would the Distutils know that, and not bother to update the Python database?) Deliverables Patches to the Distutils that 1) implement a InstallationDatabase class, 2) Update the database when a new package is installed. 3) a simple package management tool, features to be added to this PEP. (Or a separate PEP?) References [1] Michael Muller's patch (posted to the Distutils-SIG around 28 Dec 1999) generates a list of installed files. Acknowledgements Ideas for this PEP originally came from postings by Greg Ward, Fred Drake, Mats Wichmann, and others. Many changes and rewrites to this document were suggested by the readers of the Distutils SIG. Copyright This document has been placed in the public domain. Local Variables: mode: indented-text indent-tabs-mode: nil End: