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======================
Queries and Subjects
======================
.. module:: dnf.query
.. class:: Query
Facilitates lookup of packages in a :class:`~dnf.sack.Sack` based on given criteria. Query actually does not consult the information in the :class:`~!dnf.sack.Sack` until it is evaluated. The evaluation happens either explicitly using :meth:`~dnf.query.Query.run` or by iterating the query, for example::
#!/usr/bin/python3
import dnf
base = dnf.Base()
base.fill_sack()
q = base.sack.query()
i = q.installed()
i = i.filter(name='dnf')
packages = list(i) # i only gets evaluated here
print("Installed dnf package:")
for pkg in packages:
print(pkg, pkg.reponame)
or::
#!/usr/bin/python3
import dnf
base = dnf.Base()
base.read_all_repos()
base.fill_sack()
q = base.sack.query()
a = q.available()
a = a.filter(name='dnf')
print("Available dnf packages:")
for pkg in a: # a only gets evaluated here
print('{} in repo {}'.format(pkg, pkg.reponame))
Notice that none of the filtering methods mutates the state of the :class:`~dnf.query.Query` but produces a new object instead.
.. method:: available()
Returns a new query limiting the original query to the packages available from the repositories.
.. method:: difference(other)
Returns a new query that contains only those results of original query that are not in the results of the ``other`` query.
.. method:: downgrades()
Returns a new query that limits the result only to packages that can be downgrade candidates to other packages in the current set. Downgrade candidate has the same name, lower EVR and the architecture of the original and the downgrade candidate are suitable for a downgrade. Specifically, the filtering does not take any steps to establish that the downgrade candidate can actually be installed.
.. method:: duplicated()
Returns a new query that limits the result only to installed packages of same name and different version. Optional argument exclude accepts a list of package names that will be excluded from result.
.. method:: extras()
Returns a new query that limits the result to installed packages that are not present in any repo
.. method:: filter(\*\*kwargs)
Returns a new query limiting the original query to the key/value pairs from `kwargs`. Multiple `kwargs` can be passed, the filter then works by applying all of them together (logical AND). Values inside of list or query are cumulative (logical OR).
Allowed keys are:
=============== ============== ======================================================
key value type value meaning
=============== ============== ======================================================
arch string match against packages' architecture
downgrades boolean see :meth:`downgrades`. Defaults to ``False``.
empty boolean ``True`` limits to empty result set.
Defaults to ``False``.
epoch integer match against packages' epoch.
file string match against packages' files
latest integer limit to all packages of number of versions
latest_per_arch integer see :meth:`latest`.
name string match against packages' names
release string match against packages' releases
reponame string match against packages repositories' names
version string match against packages' versions
pkg Query match against packages in query
pkg* list match against hawkey.Packages in list
provides string match against packages' provides
provides* Hawkey.Reldep match against packages' provides
<DEP> string match against packages' <DEP>
<DEP>* Hawkey.Reldep match a reldep against packages' <DEP>
<DEP>* Query match the result of a query against packages' <DEP>
<DEP>* list(Package) match the list of hawkey.Packages against packages' <DEP>
sourcerpm string match against packages' source rpm
upgrades boolean see :meth:`upgrades`. Defaults to ``False``.
=============== ============== ======================================================
``<DEP>`` can be any of: requires, conflicts, obsoletes, enhances, recomments, suggests, supplements
\* The key can also accept a list of values with specified type.
The key name can be supplemented with a relation-specifying suffix, separated by ``__``:
========== =========== ==========================================================
key suffix value type semantics
========== =========== ==========================================================
eq any exact match; This is the default if no suffix is specified.
glob string shell-style wildcard match
gt integer the actual value is greater than specified
gte integer the actual value is greater than or equal to specified
lt integer the actual value is less than specified
lte integer the actual value is less than or equal to specified
neq any does not equal
substr string the specified value is contained in the actual value
========== =========== ==========================================================
For example, the following creates a query that matches all packages containing the string "club" in its name::
q = base.sack.query().filter(name__substr="club")
Note that using packages or queries for dependency filtering performs a more advanced resolution than using a string or a reldep. When a package list or a query is used, rich dependencies are resolved in a more precise way than what is possible when a string or a reldep is used.
.. method:: filterm(\*\*kwargs)
Similar to :meth:`dnf.query.Query.filter` but it modifies the query in place.
.. method:: installed()
Returns a new query that limits the result to the installed packages only.
.. method:: intersection(other)
Returns a new query where the result contains only packages that are found in both original and ``other`` queries.
.. method:: latest(limit=1)
Returns a new query that limits the result to ``limit`` highest version of packages per package
name and per architecture. In case the limit is negative number, it excludes the number of
latest versions according to limit.
.. method:: run()
Evaluate the query. Returns a list of matching :class:`dnf.package.Package` instances.
.. method:: union(other)
Returns a new query where the results of the ``other`` query are added to the results of the original query.
.. method:: upgrades()
Returns a new query that limits the result only to packages that can be upgrade candidates to at least one package in the current set. Upgrade candidate has the same name, higher EVR and the architectures of the original and the upgrade candidate package are suitable for an upgrade. Specifically, the filtering does not take any steps to establish that the upgrade candidate can actually be installed.
.. module:: dnf.subject
.. class:: Subject
As :ref:`explained on the DNF man page <specifying_packages-label>`, users of the CLI are able to select packages for an operation in different formats, leaving seemingly arbitrary parts out of the spec and even using globbing characters. This class implements a common approach to parsing such input and produce a :class:`~dnf.query.Query` listing all packages matching the input or a :class:`~dnf.selector.Selector` selecting a single package that best matches the input given a transaction operation.
.. method:: __init__(pkg_spec, ignore_case=False)
Initialize the :class:`Subject` with `pkg_spec` input string with following :ref:`semantic <specifying_packages-label>`. If `ignore_case` is ``True`` ignore the case of characters in `pkg_spec`.
.. method:: get_best_query(sack, with_nevra=True, with_provides=True, with_filenames=True, forms=None)
Returns a :class:`~Query` yielding packages matching the given input. The result of the returned
query can be an empty set if no package matches. `sack` is the :class:`~dnf.sack.Sack` that the
returned query will search. `with_nevra` enable search by nevra, `with_provides` indicates
whether besides package names also packages' provides are searched for a match, and
`with_filenames` indicates whether besides package provides also packages' file provides are
searched for a match. `forms` is a list of pattern forms from `hawkey`_. Leaving the parameter
to ``None`` results in using a reasonable default list of forms.
.. method:: get_best_selector(sack, forms=None, obsoletes=True, reponame=None)
Returns a :class:`~dnf.selector.Selector` that will select a single best-matching package when
used in a transaction operation. `sack` and `forms` have the same meaning as in
:meth:`get_best_query`. If ``obsoletes``, selector will also contain packages that obsoletes
requested packages (default is True). If ``reponame``, the selection of available packages is
limited to packages from that repo (default is None).
.. method:: get_nevra_possibilities(self, forms=None)
Returns generator for every possible nevra. Each possible nevra is represented by NEVRA class
(libdnf) that has attributes name, epoch, version, release, arch. `forms` have the same
meaning as in :meth:`get_best_query`.
Example how to use it when it is known that string could be full NEVRA or NEVR::
#!/usr/bin/python3
import dnf
import hawkey
nevra_string = "dnf-0:4.2.2-2.fc30.noarch"
subject = dnf.subject.Subject(nevra_string)
possible_nevra = subject.get_nevra_possibilities(
forms=[hawkey.FORM_NEVRA, hawkey.FORM_NEVR])
for i,nevra in enumerate(possible_nevra):
print("Possibility {} for \"{}\":".format(i+1, nevra_string))
print("name: {}".format(nevra.name))
print("epoch: {}".format(nevra.epoch))
print("version: {}".format(nevra.version))
print("release: {}".format(nevra.release))
print("architecture: {}".format(nevra.arch))
print()