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'zope.schema' extensions

Project description

This package contains extensions for zope.schema.



A companion to zope.interface.verify for the schema part of interfaces.

It contains the function verify_schema(iface, obj, context=None, check_declaration=True) which verifies that obj satisfies the schema part of interface iface. Schema fields need to get bound to a context before they can be validated. context specifies this context and defaults to obj. check_declaration checks that obj declares to privide iface.


The main content is the mixin class SchemaConfigured. It supports configuration according the schema part of the interfaces implemented by the SchemaConfigured derived class. If you want to control from which interfaces the schema is derived, you can use the class attribute SC_SCHEMAS: its value should be None (derive schema automatically from the implemented interfaces), a single interface or a tuple of interfaces. Taking explicit control over the interfaces used to determine the schema is especially important for Zope 2 schema configured content classes (as their base class OFS.SimpleItem.SimpleItem implements a huge number of interfaces whose fields you likely do not want in your schema).

The mixin class SchemaConfiguredEvolution provides support for schema evolution for (ZODB) persistent objects. Its __setstate__ adds missing attributes to the object such that you can add new fields to your schema and still find all corresponding attributes on the respective objects even when those have been created before the extension. Note: in order for SchemaConfiguredEvolution to be effective, it must come early in the method resolution order (mro) (before persistent.Persistent). That’s why is is a separate class and its feature not included in SchemaConfigured itself (there may be good reasons to have SchemaConfigured late in the mro). As an alternative to the use of SchemaConfiguredEvolution, you can use default values defined on class level for new fields.

Occasionally, functions schemaitems and schemadict might be usefull. They extract the schema part of an interface or interface specification as a list of id, field pairs or a dictionary, respectively.

The field Object is a replacement for zope.schema.Object. The latter lacks field information in validation errors ( which makes identification of the affected fields unnecessarily difficult. Occasionally, one wants to suppress the check that a validated object explicitly declares to provide the interface. Object has the additional property check_declaration to control this (defaults to True).


This module implements a schema based OFS.PropertyManager.PropertyManager subclass. The _properties attribute describing the properties is not maintained on the class or its instances but derived from the provided (respectively implemented) schemas. For the moment, properties cannot be extended on an instance based level (other than by providing another schema).

zope.schema uses unicode to represent text. PropertyManager can in principle support unicode properties. However, due to a bug/weakness, the property management page handles them correctly only, when management_page_charset is not defined or has value UTF-8 (note the upper case spelling!). We use unicode properties by default unless management_page_charset.upper() yields a value different from UTF-8. We also provide a mixin class WorkaroundSpelling_management_page_charset to work around Zope’s stupid insistence on upper case spelling for management_page_charset.

For the moment, the following field types are supported: Text, TextLine, Bytes, BytesLine`, Bool, Int, Float and List with a value type of TextLine or BytesLine. Other types will raise NotImplementedError.

The module has been implemented to leverage dm.zope.generate. An alternative would have been the implementation of the generation facilities based on “zope.formlib” and the use of so called add forms. Depending on experience, I may switch to this alternative.


The module defines default edit (SchemaConfiguredEditForm) and display (SchemaConfiguredDisplayForm) forms for dm.zope.schema.schema.SchemaConfigured.

It depends on zope.formlib.


Provides display and edit widgets for Timedelta fields, a decent display widget for Password fields (the default displays passwords in cleartext) and an input widget for Password that does not force you to provide the password value whenever you edit the form.

It depends on in older Zope versions and on zope.formlib in newer ones.


This subpackage combines schema related and Zope 2 functionality. In newer Zope versions, it depends on five.formlib.


The module defines default edit (SchemaConfiguredEditForm) and display (SchemaConfiguredDisplayForm) forms for dm.zope.schema.schema.SchemaConfigured for use in Zope 2.

It depends on zope.formlib.


This module contains an add form class SchemaConfiguredAddForm and a factory add_form_factory for the generation of an add form (called “constructor” by Zope 2) for dm.zope.schema.schema.SchemaConfigured based classes. The generated add form is usually used as part of the constructors parameter to registerClass.

add_form_factory has the parameters:





the class to generate the form for


Create instance of class_

the title shown in the form



the documentation shown in the form



form class to be used

add_form_factory generates a zope.formlib form with fields defined by the implemented schemas of dm.zope.schema.schema.SchemaConfigured class class_.

This module is similar to dm.zope.generate.constructor. However, it works for SchemaConfigured based classes while the latter supports PropertyManager based classes.


Provides the view page template form_template able to view and edit Zope 2 schema configured content objects within the standard ZMI interface.


Setup: It defines two schemas S1 and S2, an interface I and a class C deriving from SchemaConfigured implementing the schemas and the interface.

>>> from zope.interface import Interface, implements, providedBy
>>> from zope.schema import Int
>>> from dm.zope.schema.schema import SchemaConfigured
>>> from dm.zope.schema.verify import verify_schema
>>> class S1(Interface): i1 = Int(default=0)
>>> class S2(Interface): i2 = Int(default=1)
>>> class I(Interface):
...   def method(): pass
>>> class C(SchemaConfigured):
...   implements(S1, S2, I)
...   def method(self): pass

C instances have attributes corresponding to the schema fields. If no arguments are given for the constructor, they get the field default as value. Provided (keyword!) arguments override the defaults.

>>> c = C()
>>> c.i1
>>> c.i2
>>> c = C(i1=5)
>>> c.i1

The constructor rejects keyword arguments not defined in the schema in order to quickly detect spelling errors. However, this hampers the use of super in the class hierarchy for the __init__ method. Maybe, future versions will provide a means to control this check.

>>> c = C(x=5)
Traceback (most recent call last):
TypeError: non schema keyword argument: x

If the field values are appropriate, C instances provide the schemas (as verified by verify_schema). Otherwise, verify_schema will raise an exception. This example demonstrates also the elementary use of verify_schema.

>>> verify_schema(S1, c)
>>> c.i1=None
>>> verify_schema(S1, c)
Traceback (most recent call last):
zope.schema.interfaces.WrongContainedType: [('i1', RequiredMissing())]

We can create an edit (or display) form for our objects. Form fields are automatically created for our schema fields. The form classes have an customize_fields method you can override to provide custom fields and/or widgets.

Similar functionality is available for Zope 2 in the z2 subpackage.

>>> from zope.publisher.browser import TestRequest
>>> from dm.zope.schema.form import SchemaConfiguredEditForm
>>> form = SchemaConfiguredEditForm(c, TestRequest())
>>> list([f.__name__ for f in form.form_fields])
['i1', 'i2']



form support

Zope 2 constructor support

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