setuptools-51.1.0.tar.gz

Pluggable Distributions of Python Software ========================================== Distributions ------------- A "Distribution" is a collection of files that represent a "Release" of a "Project" as of a particular point in time, denoted by a "Version":: >>> import sys, pkg_resources >>> from pkg_resources import Distribution >>> Distribution(project_name="Foo", version="1.2") Foo 1.2 Distributions have a location, which can be a filename, URL, or really anything else you care to use:: >>> dist = Distribution( ... location="http://example.com/something", ... project_name="Bar", version="0.9" ... ) >>> dist Bar 0.9 (http://example.com/something) Distributions have various introspectable attributes:: >>> dist.location 'http://example.com/something' >>> dist.project_name 'Bar' >>> dist.version '0.9' >>> dist.py_version == '{}.{}'.format(*sys.version_info) True >>> print(dist.platform) None Including various computed attributes:: >>> from pkg_resources import parse_version >>> dist.parsed_version == parse_version(dist.version) True >>> dist.key # case-insensitive form of the project name 'bar' Distributions are compared (and hashed) by version first:: >>> Distribution(version='1.0') == Distribution(version='1.0') True >>> Distribution(version='1.0') == Distribution(version='1.1') False >>> Distribution(version='1.0') < Distribution(version='1.1') True but also by project name (case-insensitive), platform, Python version, location, etc.:: >>> Distribution(project_name="Foo",version="1.0") == \ ... Distribution(project_name="Foo",version="1.0") True >>> Distribution(project_name="Foo",version="1.0") == \ ... Distribution(project_name="foo",version="1.0") True >>> Distribution(project_name="Foo",version="1.0") == \ ... Distribution(project_name="Foo",version="1.1") False >>> Distribution(project_name="Foo",py_version="2.3",version="1.0") == \ ... Distribution(project_name="Foo",py_version="2.4",version="1.0") False >>> Distribution(location="spam",version="1.0") == \ ... Distribution(location="spam",version="1.0") True >>> Distribution(location="spam",version="1.0") == \ ... Distribution(location="baz",version="1.0") False Hash and compare distribution by prio/plat Get version from metadata provider capabilities egg_name() as_requirement() from_location, from_filename (w/path normalization) Releases may have zero or more "Requirements", which indicate what releases of another project the release requires in order to function. A Requirement names the other project, expresses some criteria as to what releases of that project are acceptable, and lists any "Extras" that the requiring release may need from that project. (An Extra is an optional feature of a Release, that can only be used if its additional Requirements are satisfied.) The Working Set --------------- A collection of active distributions is called a Working Set. Note that a Working Set can contain any importable distribution, not just pluggable ones. For example, the Python standard library is an importable distribution that will usually be part of the Working Set, even though it is not pluggable. Similarly, when you are doing development work on a project, the files you are editing are also a Distribution. (And, with a little attention to the directory names used, and including some additional metadata, such a "development distribution" can be made pluggable as well.) >>> from pkg_resources import WorkingSet A working set's entries are the sys.path entries that correspond to the active distributions. By default, the working set's entries are the items on ``sys.path``:: >>> ws = WorkingSet() >>> ws.entries == sys.path True But you can also create an empty working set explicitly, and add distributions to it:: >>> ws = WorkingSet([]) >>> ws.add(dist) >>> ws.entries ['http://example.com/something'] >>> dist in ws True >>> Distribution('foo',version="") in ws False And you can iterate over its distributions:: >>> list(ws) [Bar 0.9 (http://example.com/something)] Adding the same distribution more than once is a no-op:: >>> ws.add(dist) >>> list(ws) [Bar 0.9 (http://example.com/something)] For that matter, adding multiple distributions for the same project also does nothing, because a working set can only hold one active distribution per project -- the first one added to it:: >>> ws.add( ... Distribution( ... 'http://example.com/something', project_name="Bar", ... version="7.2" ... ) ... ) >>> list(ws) [Bar 0.9 (http://example.com/something)] You can append a path entry to a working set using ``add_entry()``:: >>> ws.entries ['http://example.com/something'] >>> ws.add_entry(pkg_resources.__file__) >>> ws.entries ['http://example.com/something', '...pkg_resources...'] Multiple additions result in multiple entries, even if the entry is already in the working set (because ``sys.path`` can contain the same entry more than once):: >>> ws.add_entry(pkg_resources.__file__) >>> ws.entries ['...example.com...', '...pkg_resources...', '...pkg_resources...'] And you can specify the path entry a distribution was found under, using the optional second parameter to ``add()``:: >>> ws = WorkingSet([]) >>> ws.add(dist,"foo") >>> ws.entries ['foo'] But even if a distribution is found under multiple path entries, it still only shows up once when iterating the working set: >>> ws.add_entry(ws.entries[0]) >>> list(ws) [Bar 0.9 (http://example.com/something)] You can ask a WorkingSet to ``find()`` a distribution matching a requirement:: >>> from pkg_resources import Requirement >>> print(ws.find(Requirement.parse("Foo==1.0"))) # no match, return None None >>> ws.find(Requirement.parse("Bar==0.9")) # match, return distribution Bar 0.9 (http://example.com/something) Note that asking for a conflicting version of a distribution already in a working set triggers a ``pkg_resources.VersionConflict`` error: >>> try: ... ws.find(Requirement.parse("Bar==1.0")) ... except pkg_resources.VersionConflict as exc: ... print(str(exc)) ... else: ... raise AssertionError("VersionConflict was not raised") (Bar 0.9 (http://example.com/something), Requirement.parse('Bar==1.0')) You can subscribe a callback function to receive notifications whenever a new distribution is added to a working set. The callback is immediately invoked once for each existing distribution in the working set, and then is called again for new distributions added thereafter:: >>> def added(dist): print("Added %s" % dist) >>> ws.subscribe(added) Added Bar 0.9 >>> foo12 = Distribution(project_name="Foo", version="1.2", location="f12") >>> ws.add(foo12) Added Foo 1.2 Note, however, that only the first distribution added for a given project name will trigger a callback, even during the initial ``subscribe()`` callback:: >>> foo14 = Distribution(project_name="Foo", version="1.4", location="f14") >>> ws.add(foo14) # no callback, because Foo 1.2 is already active >>> ws = WorkingSet([]) >>> ws.add(foo12) >>> ws.add(foo14) >>> ws.subscribe(added) Added Foo 1.2 And adding a callback more than once has no effect, either:: >>> ws.subscribe(added) # no callbacks # and no double-callbacks on subsequent additions, either >>> just_a_test = Distribution(project_name="JustATest", version="0.99") >>> ws.add(just_a_test) Added JustATest 0.99 Finding Plugins --------------- ``WorkingSet`` objects can be used to figure out what plugins in an ``Environment`` can be loaded without any resolution