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NTI Externalization

Project description


Latest release Supported Python versions Documentation Status

A flexible, schema-driven system for converting Python objects to and from external formats such as JSON and YAML. This works well in a zope.component environment such as Pyramid.

Documentation is hosted at


2.2.0 (2021-04-14)

  • Add support for Python 3.9.
  • Depend on BTrees 4.8 and above. This simplifies externalization checks. See issue 111.

2.1.0 (2020-08-03)

  • Add support for “externalization policies.” These are instances of ExternalizationPolicy that can be used to tweak certain low-level details of externalization without replacing externalization objects wholesale. They are intended to have a very low performance impact.

    The only supported detail that can be changed right now is whether the standard created and last modified fields are externalized as Unix timestamps (the default) or as ISO 8601 strings.


2.0.0 (2020-07-02)

  • Change ILocatedExternalMapping: Previously it extended the legacy zope.interface.common.mapping.IFullMapping. Now it extends the modern zope.interface.common.collections.IMapping. Note that this does not require mutability unlike the older interface. (The LocatedExternalDict class provided by this package is fully mutable and implements IMutableMapping. It also continues to implement IFullMapping, but use of that interface is discouraged.)
  • Change ILocatedExternalSequence: Previously it extended the legacy zope.interface.common.sequence.ISequence. Now it extends the modern zope.interface.common.collections.ISequence. Note that this does not require mutability unlike the older interface. (The LocatedExternalList class provided by this package is fully mutable and implements IMutableSequence.)
  • Fix the interface resolution order for LocatedExternalList. Previously, with zope.interface 5, it began implementing both IMutableSequence (the new interface from zope.interface.common.collections) as well as the older interface ISequence (from zope.interface.common.sequence); the two have inconsistent resolution orders. Now, it only implements IMutableSequence and a subset of the legacy interfaces that do not conflict. See issue 105.

1.1.3 (2020-06-25)

  • Correctly fire IObjectWillUpdateFromExternalEvent events before updating an object.

1.1.2 (2020-04-07)

1.1.1 (2020-03-27)

  • Fix a faulty assertion error. See issue 102.

1.1.0 (2020-03-27)

  • Make instances of fractions.Fraction externalize as a string such as "1/3". When received by a schema field that can parse this format, such as zope.schema.Rational (or higher on the numeric tower), this means fractions can be round-tripped.
  • Support externalizing decimal.Decimal objects in the YAML representation.

1.0.0 (2020-03-19)

  • Add compatibility with, and require, zope.interface 5.0.
  • Document which tagged values are inherited and which are not.
  • Stop inheriting _ext_is_marker_interface.

1.0.0a14 (2019-11-13)

  • Build with Cython 0.29.14 using ‘3str’ as the language level.
  • Add support for Python 3.8.
  • Update PyYAML to 5.1 and change the default output style slightly.
  • Fix tests with Persistent 4.4.3 and above.
  • Support zope.interface 4.7, which lets tagged values on interfaces be inherited, when using <registerAutoPackageIO> on a module that had multiple objects implementing a derived interface. See issue 97.

1.0.0a13 (2018-09-20)

  • Support IFromBytes fields introduced by zope.schema 4.8.0. See issue 92.
  • Make validate_field_value (and by extension InterfaceObjectIO.update_from_external_object) call fromObject defined by any fields for non-byte and non-text data. Previously, only if the field raised a WrongContainedTypeError would fromObject be called.

1.0.0a12 (2018-09-11)

  • Add support for zope.schema 4.7.0 and nti.schema 1.5.0. Drop support for older versions, which includes dropping support for dm.zope.schema.Object fields.

1.0.0a11 (2018-08-29)

  • The @WithRepr decorator takes into account the updated default repr of Persistent objects with persistent 4.4 and doesn’t hide it.
  • Subclasses of ExternalizableInstanceDict that have non-str (unicode on Python 2, bytes on Python 3) keys in their __dict__ do not throw TypeError when externalizing. Instead, the non-str values are converted to strs (using ASCII encoding) and the _p_changed attribute, if any, is set.

1.0.0a10 (2018-08-21)

  • The registry argument to most functions is deprecated and ignored. Instead of making calls to registry.queryAdapter, we now invoke the interface directly. For example, IInternalObjectExternalizer(containedObject). This lets individual objects have a say if they already provide the interface without going through the legacy code paths (it also calls __conform__ on the object if needed).

1.0.0a9 (2018-08-20)

  • Allow subclasses of InterfaceObjectIO to have non-frozenset values for _ext_primitive_out_ivars_. This issues a warning and in the future will be a TypeError.

1.0.0a8 (2018-08-16)

  • Better support for internalizing anonymous value objects discovered in a Dict value. Now, they won’t raise a ComponentLookupError when require_updater is True, and they will be given a MimeType based on the schema (if they don’t have one).

1.0.0a7 (2018-07-31)

  • Avoid a TypeError from validate_named_field_value when external objects have unicode keys.
  • LocatedExternalDict objects accept more constructor arguments and allow arbitrary attributes.

1.0.0a6 (2018-07-31)

  • InterfaceObjectIO only returns an anonymous factory for IDict fields when it wants objects for the value.
  • StandardExternalFields and StandardInternalFields are deprecated aliases in nti.externalization.externalization.
  • update_from_external_object properly handles the case where INamedExternalizedObjectFactoryFinder and IInternalObjectUpdater are registered with different levels of specificity, and the finder also implements IInternalObjectUpdater. Before, the finder would, perhaps incorrectly, be used as the updater.

1.0.0a5 (2018-07-30)

  • Objects inheriting from InterfaceObjectIO and registered with the component registry (in ZCML) for IInternalObjectIO can still be found and used as INamedExternalizedObjectFactoryFinder, an interface implemented by InterfaceObjectIO through IInternalObjectIOFinder. A warning will be issued to update the registration (which generally means removing the provides line in ZCML).
  • ExternalizableInstanceDict no longer inherits from AbstractDynamicIO, it just implements the same interface (with the exception of many of the _ext methods). This class is deprecated.
  • Formally document the notify_modified member of nti.externalization.internalization. notifyModified is a deprecated alias.

1.0.0a4 (2018-07-30)

  • Make InterfaceObjectIO._ext_self readable from Python, even though that is not documented (and may change again in the future). Document the intended API, _ext_replacement(). See issue 73.
  • Make AbstractDynamicObjectIO._ext_getattr handle a default value, and add _ext_replacement_getattr for when it will only be called once. See issue 73.

1.0.0a3 (2018-07-28)

  • The @NoPickle decorator also works with Persistent subclasses (and may or may not work with multiple-inheritance subclasses of Persistent, depending on the MRO, but that’s always been the case for regular objects). A Persistent subclass being decorated with @NoPickle doesn’t make much sense, so a RuntimeWarning is issued. A warning is also issued if the class directly implements one of the pickle protocol methods.
  • Updating objects that use createFieldProperties or otherwise have FieldProperty objects in their type is at least 10% faster thanks to avoiding double-validation due to a small monkey-patch on FieldProperty. See issue 67.
  • Proxies around objects that implement toExternalObject are allowed again; the proxied object’s toExternalObject will be called.
  • The signature for updateFromExternalObject() has been tightened. It should be (self, external_object, context, **kwargs), where **kwargs is optional, as is context. **kwargs currently contains nothing useful. Uses of dataserver=None in the signature will generate a warning. This may be tightened further in the future. See issue 30.
  • __ext_ignore_updateFromExternalObject__ is officially deprecated and generates a warning.
  • update_from_external_object caches certain information about the types of the updater objects, making it 8-25% faster.
  • update_from_external_object mutates sequences contained in a dict in-place instead of overwriting with a new list.
  • update_from_external_object mutates sequences at the top level instead of returning a new list.
  • Add support for finding factories for incoming data which do not specify a MIME type or class field based on the key they are assigned to. This aids in consuming data produced by foreign systems or using Dict schema fields that require modelled values. See issue 51 and PR 68.
  • Schemas that use InterfaceObjectIO (including through the ZCML directive registerAutoPackageIO) can use Dict fields more easily on internalization (externalization has always worked): They automatically internalize their values by treating the Dict as anonymous external data.
  • Strings can automatically be adapted into ITimeDelta objects.

1.0.0a2 (2018-07-05)

  • The low levels of externalization no longer catch and hide POSKeyError. This indicates a problem with the database. See
  • Remove support for object_hook in update_from_external_object. See
  • A number of deprecated aliases for moved functions have been removed.
  • On CPython, some of the modules are compiled as extension modules using Cython for a 10-30% increase in speed. Set the PURE_PYTHON environment variable to disable this at runtime.
  • The unused, undocumented method stripSyntheticKeysFromExternalDictionary was removed from instances of ExternalizableDictionaryMixin. Use the import instead.
  • Unused keyword arguments for to_standard_external_dictionary and to_minimal_standard_external_dictionary now produce a warning. In the future, extra keyword arguments will be an error.
  • notifyModified no longer accepts the eventFactory argument.
  • The notify_modified alias for notifyModified has been removed.
  • Decorating external mappings and external objects handled decorate_callback differently. This argument is only used when decorate is false. This argument is also confusing and should be considered deprecated.
  • choose_field no longer has the undocumented conversion behaviour for the CREATOR external field name.

1.0.0a1 (2017-09-29)

  • First PyPI release.
  • Add support for Python 3.
  • Drop support for externalizing to plists. See
  • Reach 100% test coverage and ensure we remain there through CI.
  • Introduce nti.externalization.extension_points to hold hook functions. Move the Pyramid integration there (and deprecate that). Also move the NTIID support there (but the old name works too). See
  • Deprecate nti.externalization.internalization.register_legacy_search_module. See
  • Stop ext:registerAutoPackageIO from registering the legacy class-name based factories by default. If you need class-name based factories, there are two options. The first is to explicitly register IClassObjectFactory objects in ZCML (we could add a scanning directive to make that more convenient for large numbers of classes), and the second is to set register_legacy_search_module to a true value in the ZCML directive for ext:registerAutoPackageIO. Note that we expect the behaviour of this attribute to change in the near future. See
  • Make ext:registerAutoPackageIO perform legacy class registrations when the configuration context executes, not when the directive runs. This means that conflicts in legacy class names will be detected at configuration time. It also means that legacy class names can be registered locally with z3c.baseregistry (previously they were always registered in the global site manager). See
  • Drop dependency on zope.preference and zope.annotation. They were not used by this package, although our configure.zcml did include them. If you use zope.preference or zope.annotation, please include them in your own ZCML file.
  • Drop hard dependency on Acquisition. It is still used if available and is used in test mode.
  • Add public implementations of IMimeObjectFactory and IClassObjectFactory in nti.externalization.factory.
  • Drop dependency on nti.zodb and its PersistentPropertyHolder. The datastructures in nti.externalization.persistence no longer extend that class; if you have further subclasses that add nti.zodb.peristentproperty.PropertyHoldingPersistent properties, you’ll need to be sure to mixin this class now. See
  • Add the <ext:classObjectFactory> directive for registering Class based factories. (Note: MIME factories are preferred.)
  • Callers of to_standard_external_dictionary (which includes AutoPackageScopedInterfaceIO) will now automatically get a MimeType value if one can be found. Previously only callers of to_minimal_standard_external_dictionary would.

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