5.2.1 (unreleased)

  • Nothing changed yet.

5.2.0 (2020-11-05)

  • Add documentation section Persistency and Equality (#218).
  • Create arm64 wheels.
  • Add support for Python 3.9.

5.1.2 (2020-10-01)

  • Make sure to call each invariant only once when validating invariants. Previously, invariants could be called multiple times because when an invariant is defined in an interface, it’s found by in all interfaces inheriting from that interface. See pull request 215.

5.1.1 (2020-09-30)

  • Fix the method definitions of IAdapterRegistry.subscribe, subscriptions and subscribers. Previously, they all were defined to accept a name keyword argument, but subscribers have no names and the implementation of that interface did not accept that argument. See issue 208.

  • Fix a potential reference leak in the C optimizations. Previously, applications that dynamically created unique Specification objects (e.g., used @implementer on dynamic classes) could notice a growth of small objects over time leading to increased garbage collection times. See issue 216.


    This leak could prevent interfaces used as the bases of other interfaces from being garbage collected. Those interfaces will now be collected.

    One way in which this would manifest was that weakref.ref objects (and things built upon them, like Weak[Key|Value]Dictionary) would continue to have access to the original object even if there were no other visible references to Python and the original object should have been collected. This could be especially problematic for the WeakKeyDictionary when combined with dynamic or local (created in the scope of a function) interfaces, since interfaces are hashed based just on their name and module name. See the linked issue for an example of a resulting KeyError.

    Note that such potential errors are not new, they are just once again a possibility.

5.1.0 (2020-04-08)

  • Make @implementer(*iface) and classImplements(cls, *iface) ignore redundant interfaces. If the class already implements an interface through inheritance, it is no longer redeclared specifically for cls. This solves many instances of inconsistent resolution orders, while still allowing the interface to be declared for readability and maintenance purposes. See issue 199.

  • Remove all bare except: statements. Previously, when accessing special attributes such as __provides__, __providedBy__, __class__ and __conform__, this package wrapped such access in a bare except: statement, meaning that many errors could pass silently; typically this would result in a fallback path being taken and sometimes (like with providedBy()) the result would be non-sensical. This is especially true when those attributes are implemented with descriptors. Now, only AttributeError is caught. This makes errors more obvious.

    Obviously, this means that some exceptions will be propagated differently than before. In particular, RuntimeError raised by Acquisition in the case of circular containment will now be propagated. Previously, when adapting such a broken object, a TypeError would be the common result, but now it will be a more informative RuntimeError.

    In addition, ZODB errors like POSKeyError could now be propagated where previously they would ignored by this package.

    See issue 200.

  • Require that the second argument (bases) to InterfaceClass is a tuple. This only matters when directly using InterfaceClass to create new interfaces dynamically. Previously, an individual interface was allowed, but did not work correctly. Now it is consistent with type and requires a tuple.

  • Let interfaces define custom __adapt__ methods. This implements the other side of the PEP 246 adaptation protocol: objects being adapted could already implement __conform__ if they know about the interface, and now interfaces can implement __adapt__ if they know about particular objects. There is no performance penalty for interfaces that do not supply custom __adapt__ methods.

    This includes the ability to add new methods, or override existing interface methods using the new @interfacemethod decorator.

    See issue 3.

  • Make the internal singleton object returned by APIs like implementedBy and directlyProvidedBy for objects that implement or provide no interfaces more immutable. Previously an internal cache could be mutated. See issue 204.

5.0.2 (2020-03-30)

  • Ensure that objects that implement no interfaces (such as direct subclasses of object) still include Interface itself in their __iro___ and __sro___. This fixes adapter registry lookups for such objects when the adapter is registered for Interface. See issue 197.

5.0.1 (2020-03-21)

  • Ensure the resolution order for InterfaceClass is consistent. See issue 192.
  • Ensure the resolution order for collections.OrderedDict is consistent on CPython 2. (It was already consistent on Python 3 and PyPy).
  • Fix the handling of the ZOPE_INTERFACE_STRICT_IRO environment variable. Previously, ZOPE_INTERFACE_STRICT_RO was read, in contrast with the documentation. See issue 194.

5.0.0 (2020-03-19)

  • Make an internal singleton object returned by APIs like implementedBy and directlyProvidedBy immutable. Previously, it was fully mutable and allowed changing its __bases___. That could potentially lead to wrong results in pathological corner cases. See issue 158.

  • Support the PURE_PYTHON environment variable at runtime instead of just at wheel build time. A value of 0 forces the C extensions to be used (even on PyPy) failing if they aren’t present. Any other value forces the Python implementation to be used, ignoring the C extensions. See PR 151.

  • Cache the result of __hash__ method in InterfaceClass as a speed optimization. The method is called very often (i.e several hundred thousand times during Plone 5.2 startup). Because the hash value never changes it can be cached. This improves test performance from 0.614s down to 0.575s (1.07x faster). In a real world Plone case a reindex index came down from 402s to 320s (1.26x faster). See PR 156.

  • Change the C classes SpecificationBase and its subclass ClassProvidesBase to store implementation attributes in their structures instead of their instance dictionaries. This eliminates the use of an undocumented private C API function, and helps make some instances require less memory. See PR 154.

  • Reduce memory usage in other ways based on observations of usage patterns in Zope (3) and Plone code bases.

    • Specifications with no dependents are common (more than 50%) so avoid allocating a WeakKeyDictionary unless we need it.
    • Likewise, tagged values are relatively rare, so don’t allocate a dictionary to hold them until they are used.
    • Use __slots___ or the C equivalent tp_members in more common places. Note that this removes the ability to set arbitrary instance variables on certain objects. See PR 155.

    The changes in this release resulted in a 7% memory reduction after loading about 6,000 modules that define about 2,200 interfaces.


    Details of many private attributes have changed, and external use of those private attributes may break. In particular, the lifetime and default value of _v_attrs has changed.

  • Remove support for hashing uninitialized interfaces. This could only be done by subclassing InterfaceClass. This has generated a warning since it was first added in 2011 (3.6.5). Please call the InterfaceClass constructor or otherwise set the appropriate fields in your subclass before attempting to hash or sort it. See issue 157.

  • Remove unneeded override of the __hash__ method from zope.interface.declarations.Implements. Watching a reindex index process in ZCatalog with on a Py-Spy after 10k samples the time for .adapter._lookup was reduced from 27.5s to 18.8s (~1.5x faster). Overall reindex index time shrunk from 369s to 293s (1.26x faster). See PR 161.

  • Make the Python implementation closer to the C implementation by ignoring all exceptions, not just AttributeError, during (parts of) interface adaptation. See issue 163.

  • Micro-optimization in .adapter._lookup , .adapter._lookupAll and .adapter._subscriptions: By loading components.get into a local variable before entering the loop a bytcode “LOAD_FAST 0 (components)” in the loop can be eliminated. In Plone, while running all tests, average speedup of the “owntime” of _lookup is ~5x. See PR 167.

  • Add __all__ declarations to all modules. This helps tools that do auto-completion and documentation and results in less cluttered results. Wildcard (“*”) are not recommended and may be affected. See issue 153.

  • Fix verifyClass and verifyObject for builtin types like dict that have methods taking an optional, unnamed argument with no default value like dict.pop. On PyPy3, the verification is strict, but on PyPy2 (as on all versions of CPython) those methods cannot be verified and are ignored. See issue 118.

  • Update the common interfaces IEnumerableMapping, IExtendedReadMapping, IExtendedWriteMapping, IReadSequence and IUniqueMemberWriteSequence to no longer require methods that were removed from Python 3 on Python 3, such as __setslice___. Now, dict, list and tuple properly verify as IFullMapping, ISequence and IReadSequence, respectively on all versions of Python.

  • Add human-readable __str___ and __repr___ to Attribute and Method. These contain the name of the defining interface and the attribute. For methods, it also includes the signature.

  • Change the error strings raised by verifyObject and verifyClass. They now include more human-readable information and exclude extraneous lines and spaces. See issue 170.


    This will break consumers (such as doctests) that depended on the exact error messages.

  • Make verifyObject and verifyClass report all errors, if the candidate object has multiple detectable violations. Previously they reported only the first error. See issue.

    Like the above, this will break consumers depending on the exact output of error messages if more than one error is present.

  • Add zope.interface.common.collections, zope.interface.common.numbers, and These modules define interfaces based on the ABCs defined in the standard library, numbers and io modules, respectively. Importing these modules will make the standard library concrete classes that are registered with those ABCs declare the appropriate interface. See issue 138.

  • Add zope.interface.common.builtins. This module defines interfaces of common builtin types, such as ITextString and IByteString, IDict, etc. These interfaces extend the appropriate interfaces from collections and numbers, and the standard library classes implement them after importing this module. This is intended as a replacement for third-party packages like dolmen.builtins. See issue 138.

  • Make providedBy() and implementedBy() respect super objects. For instance, if class Derived implements IDerived and extends Base which in turn implements IBase, then providedBy(super(Derived, derived)) will return [IBase]. Previously it would have returned [IDerived] (in general, it would previously have returned whatever would have been returned without super).

    Along with this change, adapter registries will unpack super objects into their __self___ before passing it to the factory. Together, this means that component.getAdapter(super(Derived, self), ITarget) is now meaningful.

    See issue 11.

  • Fix a potential interpreter crash in the low-level adapter registry lookup functions. See issue 11.

  • Adopt Python’s standard C3 resolution order to compute the __iro__ and __sro__ of interfaces, with tweaks to support additional cases that are common in interfaces but disallowed for Python classes. Previously, an ad-hoc ordering that made no particular guarantees was used.

    This has many beneficial properties, including the fact that base interface and base classes tend to appear near the end of the resolution order instead of the beginning. The resolution order in general should be more predictable and consistent.


    In some cases, especially with complex interface inheritance trees or when manually providing or implementing interfaces, the resulting IRO may be quite different. This may affect adapter lookup.

    The C3 order enforces some constraints in order to be able to guarantee a sensible ordering. Older versions of zope.interface did not impose similar constraints, so it was possible to create interfaces and declarations that are inconsistent with the C3 constraints. In that event, zope.interface will still produce a resolution order equal to the old order, but it won’t be guaranteed to be fully C3 compliant. In the future, strict enforcement of C3 order may be the default.

    A set of environment variables and module constants allows controlling several aspects of this new behaviour. It is possible to request warnings about inconsistent resolution orders encountered, and even to forbid them. Differences between the C3 resolution order and the previous order can be logged, and, in extreme cases, the previous order can still be used (this ability will be removed in the future). For details, see the documentation for

  • Make inherited tagged values in interfaces respect the resolution order (__iro__), as method and attribute lookup does. Previously tagged values could give inconsistent results. See issue 190.

  • Add getDirectTaggedValue (and related methods) to interfaces to allow accessing tagged values irrespective of inheritance. See issue 190.

  • Ensure that Interface is always the last item in the __iro__ and __sro__. This is usually the case, but if classes that do not implement any interfaces are part of a class inheritance hierarchy, Interface could be assigned too high a priority. See issue 8.

  • Implement sorting, equality, and hashing in C for Interface objects. In micro benchmarks, this makes those operations 40% to 80% faster. This translates to a 20% speed up in querying adapters.

    Note that this changes certain implementation details. In particular, InterfaceClass now has a non-default metaclass, and it is enforced that __module__ in instances of InterfaceClass is read-only.

    See PR 183.

4.7.2 (2020-03-10)

  • Remove deprecated use of setuptools features. See issue 30.

4.7.1 (2019-11-11)

  • Use Python 3 syntax in the documentation. See issue 119.

4.7.0 (2019-11-11)

  • Drop support for Python 3.4.

  • Change queryTaggedValue, getTaggedValue, getTaggedValueTags in interfaces. They now include inherited values by following __bases__. See PR 144.


    This may be a breaking change.

  • Add support for Python 3.8.

4.6.0 (2018-10-23)

  • Add support for Python 3.7
  • Fix verifyObject for class objects with staticmethods on Python 3. See issue 126.

4.5.0 (2018-04-19)

  • Drop support for 3.3, avoid accidental dependence breakage via See PR 110.
  • Allow registering and unregistering instance methods as listeners. See issue 12 and PR 102.
  • Synchronize and simplify zope/ See issue 114

4.4.3 (2017-09-22)

  • Avoid exceptions when the __annotations__ attribute is added to interface definitions with Python 3.x type hints. See issue 98.
  • Fix the possibility of a rare crash in the C extension when deallocating items. See issue 100.

4.4.2 (2017-06-14)

  • Fix a regression storing zope.component.persistentregistry.PersistentRegistry instances. See issue 85.
  • Fix a regression that could lead to the utility registration cache of Components getting out of sync. See issue 93.

4.4.1 (2017-05-13)

  • Simplify the caching of utility-registration data. In addition to simplification, avoids spurious test failures when checking for leaks in tests with persistent registries. See pull 84.
  • Raise ValueError when non-text names are passed to adapter registry methods: prevents corruption of lookup caches.

4.4.0 (2017-04-21)

4.3.3 (2016-12-13)

4.3.2 (2016-09-05)

4.3.1 (2016-08-31)

4.3.0 (2016-08-31)

4.2.0 (2016-06-10)

  • Add support for Python 3.5
  • Drop support for Python 2.6 and 3.2.

4.1.3 (2015-10-05)

4.1.2 (2014-12-27)

  • Add support for PyPy3.
  • Remove unittest assertions deprecated in Python3.x.
  • Add zope.interface.document.asReStructuredText, which formats the generated text for an interface using ReST double-backtick markers.

4.1.1 (2014-03-19)

  • Add support for Python 3.4.

4.1.0 (2014-02-05)

  • Update to version 2.2.
  • Add @named(name) declaration, that specifies the component name, so it does not have to be passed in during registration.

4.0.5 (2013-02-28)

  • Fix a bug where a decorated method caused false positive failures on verifyClass().

4.0.4 (2013-02-21)

  • Fix a bug that was revealed by porting zope.traversing. During a loop, the loop body modified a weakref dict causing a RuntimeError error.

4.0.3 (2012-12-31)

  • Fleshed out PyPI Trove classifiers.

4.0.2 (2012-11-21)

  • Add support for Python 3.3.
  • Restored ability to install the package in the absence of setuptools.
  • LP #1055223: Fix test which depended on dictionary order and failed randomly in Python 3.3.

4.0.1 (2012-05-22)

  • Drop explicit DeprecationWarnings for “class advice” APIS (these APIs are still deprecated under Python 2.x, and still raise an exception under Python 3.x, but no longer cause a warning to be emitted under Python 2.x).

4.0.0 (2012-05-16)

  • Automated build of Sphinx HTML docs and running doctest snippets via tox.
  • Deprecate the “class advice” APIs from zope.interface.declarations: implements, implementsOnly, and classProvides. In their place, prefer the equivalent class decorators: @implementer, @implementer_only, and @provider. Code which uses the deprecated APIs will not work as expected under Py3k.
  • Remove use of ‘2to3’ and associated fixers when installing under Py3k. The code is now in a “compatible subset” which supports Python 2.6, 2.7, and 3.2, including PyPy 1.8 (the version compatible with the 2.7 language spec).
  • Drop explicit support for Python 2.4 / 2.5 / 3.1.
  • Add support for PyPy.
  • Add support for continuous integration using tox and jenkins.
  • Add ‘ dev’ alias (runs develop plus installs nose and coverage).
  • Add ‘ docs’ alias (installs Sphinx and dependencies).
  • Replace all unittest coverage previously accomplished via doctests with unittests. The doctests have been moved into a docs section, managed as a Sphinx collection.
  • LP #910987: Ensure that the semantics of the lookup method of zope.interface.adapter.LookupBase are the same in both the C and Python implementations.
  • LP #900906: Avoid exceptions due to tne new __qualname__ attribute added in Python 3.3 (see PEP 3155 for rationale). Thanks to Antoine Pitrou for the patch.

3.8.0 (2011-09-22)

  • New module zope.interface.registry. This is code moved from zope.component.registry which implements a basic nonperistent component registry as zope.interface.registry.Components. This class was moved from zope.component to make porting systems (such as Pyramid) that rely only on a basic component registry to Python 3 possible without needing to port the entirety of the zope.component package. Backwards compatibility import shims have been left behind in zope.component, so this change will not break any existing code.
  • New tests_require dependency: zope.event to test events sent by Components implementation. The zope.interface package does not have a hard dependency on zope.event, but if zope.event is importable, it will send component registration events when methods of an instance of zope.interface.registry.Components are called.
  • New interfaces added to support zope.interface.registry.Components addition: ComponentLookupError, Invalid, IObjectEvent, ObjectEvent, IComponentLookup, IRegistration, IUtilityRegistration, IAdapterRegistration, ISubscriptionAdapterRegistration, IHandlerRegistration, IRegistrationEvent, RegistrationEvent, IRegistered, Registered, IUnregistered, Unregistered, IComponentRegistry, and IComponents.
  • No longer Python 2.4 compatible (tested under 2.5, 2.6, 2.7, and 3.2).

3.7.0 (2011-08-13)

  • Move changes from 3.6.2 - 3.6.5 to a new 3.7.x release line.

3.6.7 (2011-08-20)

  • Fix sporadic failures on x86-64 platforms in tests of rich comparisons of interfaces.

3.6.6 (2011-08-13)

  • LP #570942: Now correctly compare interfaces from different modules but with the same names.

    N.B.: This is a less intrusive / destabilizing fix than the one applied in 3.6.3: we only fix the underlying cmp-alike function, rather than adding the other “rich comparison” functions.

  • Revert to software as released with 3.6.1 for “stable” 3.6 release branch.

3.6.5 (2011-08-11)

  • LP #811792: work around buggy behavior in some subclasses of zope.interface.interface.InterfaceClass, which invoke __hash__ before initializing __module__ and __name__. The workaround returns a fixed constant hash in such cases, and issues a UserWarning.
  • LP #804832: Under PyPy, zope.interface should not build its C extension. Also, prevent attempting to build it under Jython.
  • Add a tox.ini for easier xplatform testing.
  • Fix testing deprecation warnings issued when tested under Py3K.

3.6.4 (2011-07-04)

  • LP 804951: InterfaceClass instances were unhashable under Python 3.x.

3.6.3 (2011-05-26)

  • LP #570942: Now correctly compare interfaces from different modules but with the same names.

3.6.2 (2011-05-17)

  • Moved detailed documentation out-of-line from PyPI page, linking instead to .
  • Fixes for small issues when running tests under Python 3.2 using zope.testrunner.
  • LP # 675064: Specify return value type for C optimizations module init under Python 3: undeclared value caused warnings, and segfaults on some 64 bit architectures.
  • now raises RuntimeError if you don’t have Distutils installed when running under Python 3.

3.6.1 (2010-05-03)

  • A non-ASCII character in the changelog made 3.6.0 uninstallable on Python 3 systems with another default encoding than UTF-8.
  • Fix compiler warnings under GCC 4.3.3.

3.6.0 (2010-04-29)

  • LP #185974: Clear the cache used by Specificaton.get inside Specification.changed. Thanks to Jacob Holm for the patch.

  • Add support for Python 3.1. Contributors:

    Lennart Regebro Martin v Loewis Thomas Lotze Wolfgang Schnerring

    The 3.1 support is completely backwards compatible. However, the implements syntax used under Python 2.X does not work under 3.X, since it depends on how metaclasses are implemented and this has changed. Instead it now supports a decorator syntax (also under Python 2.X):

    class Foo:

    can now also be written:

    class Foo:

    There are 2to3 fixers available to do this change automatically in the zope.fixers package.

  • Python 2.3 is no longer supported.

3.5.4 (2009-12-23)

  • Use the standard Python doctest module instead of zope.testing.doctest, which has been deprecated.

3.5.3 (2009-12-08)

3.5.2 (2009-07-01)

  • BaseAdapterRegistry.unregister, unsubscribe: Remove empty portions of the data structures when something is removed. This avoids leaving references to global objects (interfaces) that may be slated for removal from the calling application.

3.5.1 (2009-03-18)

  • verifyObject: use getattr instead of hasattr to test for object attributes in order to let exceptions other than AttributeError raised by properties propagate to the caller
  • Add Sphinx-based documentation building to the package buildout configuration. Use the bin/docs command after buildout.
  • Improve package description a bit. Unify changelog entries formatting.
  • Change package’s mailing list address to zope-dev at as zope3-dev at is now retired.

3.5.0 (2008-10-26)

  • Fix declaration of _zope_interface_coptimizations, it’s not a top level package.
  • Add a DocTestSuite for module, so their tests are run.
  • Allow to bootstrap on Jython.
  • Fix ISpecification was missing a declaration for __iro__.
  • Add optional code optimizations support, which allows the building of C code optimizations to fail (Jython).
  • Replace _flatten with a non-recursive implementation, effectively making it 3x faster.

3.4.1 (2007-10-02)

  • Fix a setup bug that prevented installation from source on systems without setuptools.

3.4.0 (2007-07-19)

  • Final release for 3.4.0.

3.4.0b3 (2007-05-22)

  • When checking whether an object is already registered, use identity comparison, to allow adding registering with picky custom comparison methods. (2007-01-03)

  • Made a reference to OverflowWarning, which disappeared in Python 2.5, conditional.

3.3.0 (2007/01/03)

New Features

  • Refactor the adapter-lookup algorithim to make it much simpler and faster.

    Also, implement more of the adapter-lookup logic in C, making debugging of application code easier, since there is less infrastructre code to step through.

  • Treat objects without interface declarations as if they declared that they provide zope.interface.Interface.

  • Add a number of richer new adapter-registration interfaces that provide greater control and introspection.

  • Add a new interface decorator to zope.interface that allows the setting of tagged values on an interface at definition time (see zope.interface.taggedValue).

Bug Fixes

  • A bug in multi-adapter lookup sometimes caused incorrect adapters to be returned. (2006-04-15)

  • Fix packaging bug: ‘package_dir’ must be a relative path. (2006-04-14)

  • Packaging change: suppress inclusion of ‘setup.cfg’ in ‘sdist’ builds.

3.2.0 (2006-01-05)

  • Corresponds to the verison of the zope.interface package shipped as part of the Zope 3.2.0 release.

3.1.0 (2005-10-03)

  • Corresponds to the verison of the zope.interface package shipped as part of the Zope 3.1.0 release.
  • Made attribute resolution order consistent with component lookup order, i.e. new-style class MRO semantics.
  • Deprecate ‘isImplementedBy’ and ‘isImplementedByInstancesOf’ APIs in favor of ‘implementedBy’ and ‘providedBy’.

3.0.1 (2005-07-27)

  • Corresponds to the verison of the zope.interface package shipped as part of the Zope X3.0.1 release.
  • Fix a bug reported by James Knight, which caused adapter registries to fail occasionally to reflect declaration changes.

3.0.0 (2004-11-07)

  • Corresponds to the verison of the zope.interface package shipped as part of the Zope X3.0.0 release.