ZConfig.datatypes — Default data type registry

Default implementation of a data type registry

This module provides the implementation of the default data type registry and all the standard data types supported by ZConfig. A number of convenience classes are also provided to assist in the creation of additional data types.

A “data type registry” is an object that provides conversion functions for data types. The interface for a registry is fairly simple.

A “conversion function” is any callable object that accepts a single argument and returns a suitable value, or raises an exception if the input value is not acceptable. ValueError is the preferred exception for disallowed inputs, but any other exception will be properly propagated.

class ZConfig.datatypes.Registry(stock=None)

Implementation of a simple type registry.

If given, stock should be a mapping which defines the “built-in” data types for the registry; if omitted or None, the standard set of data types is used (see Standard ZConfig Datatypes).


Return the type conversion routine for name.

If the conversion function cannot be found, an (unspecified) exception is raised. If the name is not provided in the stock set of data types by this registry and has not otherwise been registered, this method uses the search() method to load the conversion function. This is the only method the rest of ZConfig requires.

register(name, conversion)

Register the data type name name to use the conversion function conversion.

If name is already registered or provided as a stock data type, ValueError is raised (this includes the case when name was found using the search() method).


This is a helper method for the default implementation of the get() method.

If name is a Python dotted-name, this method loads the value for the name by dynamically importing the containing module and extracting the value of the name. The name must refer to a usable conversion function.

The following classes are provided to define conversion functions:

class ZConfig.datatypes.MemoizedConversion(conversion)

Simple memoization for potentially expensive conversions.

This conversion helper caches each successful conversion for re-use at a later time; failed conversions are not cached in any way, since it is difficult to raise a meaningful exception providing information about the specific failure.

class ZConfig.datatypes.RangeCheckedConversion(conversion, min=None, max=None)

Conversion helper that performs range checks on the result of another conversion.

Values passed to instances of this conversion are converted using conversion and then range checked. min and max, if given and not None, are the inclusive endpoints of the allowed range. Values returned by conversion which lay outside the range described by min and max cause ValueError to be raised.

class ZConfig.datatypes.RegularExpressionConversion(regex)

Conversion that checks that the input matches the regular expression regex.

If it matches, returns the input, otherwise raises ValueError.