The pattern method on a match iterator allows you to refine a query. This narrows an existing iterator to only show the packages you desire. The basic syntax follows:

mi.pattern(tag_name, mode, pattern)

The two main uses of the pattern method are to query on more than one tag, such as the version and name, or to narrow the results of a query, using the rich set of pattern modes. The mode parameter names the type of pattern used, which can be one of those listed in Table 17-2.

Table 17-2 Pattern modes for the pattern method

Cross Reference

For more on these patterns, see the online manual pages for fnmatch(3), glob(7), regcomp(3), regex(7), and strcmp(3). The pattern method calls rpmdbSetIteratorRE from the C API, covered in the “Database Iterators” section in Chapter 15, Programming RPM with C .

To query for all packages starting with py, for example, you can use code like the following:

import rpm

ts = rpm.TransactionSet()

mi = ts.dbMatch()

mi.pattern('name', rpm.RPMMIRE_GLOB, 'py*' )

for h in mi:

# Do something with the header...

Listing 17-4 shows an example for glob-based querying.

Listing 17-4: rpmglob.py

#!/usr/bin/python

# Acts like rpm -q and lists the N-V-R for installed packages

# that match a given name using a glob-like syntax

#

# Usage:

# python rpmglob.py "package_fragment*"

import rpm, sys

ts = rpm.TransactionSet()

mi = ts.dbMatch()

if not mi:

print "No packages found."

else:

mi.pattern('name', rpm.RPMMIRE_GLOB, sys.argv[1] )

for h in mi:

print "%s-%s-%s" % (h['name'], h['version'], h['release'])

When you run this script, you’ll see output like the following:

$ python rpmglob.py "py*"

pyxf86config-0.3.1-2

python-devel-2.2.1-17

pygtk2-devel-1.99.12-7

pygtk2-libglade-1.99.12-7

pygtk2-1.99.12-7

pyOpenSSL-0.5.0.91-1

python-optik-1.3-2

python-docs-2.2.1-17

python-2.2.1-17

python-tools-2.2.1-17

In addition to working with the RPM database, the Python API also provides access to RPM files.