UserDict — Class wrapper for dictionary objects¶The module defines a mixin, DictMixin, defining all dictionary methods for classes that already have a minimum mapping interface. This greatly simplifies writing classes that need to be substitutable for dictionaries (such as the shelve module). This module also defines a class, UserDict, that acts as a wrapper around dictionary objects. The need for this class has been largely supplanted by the ability to subclass directly from dict (a feature that became available starting with Python version 2.2). Prior to the introduction of dict, the UserDict class was used to create dictionary-like sub-classes that obtained new behaviors by overriding existing methods or adding new ones. The UserDict module defines the UserDict class and DictMixin:
In addition to supporting the methods and operations of mappings (see section Mapping Types — dict), UserDict and IterableUserDict instances provide the following attribute:
UserList — Class wrapper for list objects¶Note This module is available for backward compatibility only. If you are writing code that does not need to work with versions of Python earlier than Python 2.2, please consider subclassing directly from the built-in list type. This module defines a class that acts as a wrapper around list objects. It is a useful base class for your own list-like classes, which can inherit from them and override existing methods or add new ones. In this way one can add new behaviors to lists. The UserList module defines the UserList class:
In addition to supporting the methods and operations of mutable sequences (see section Sequence Types — str, unicode, list, tuple, buffer, xrange), UserList instances provide the following attribute: Subclassing requirements: Subclasses of UserList are expect to offer a constructor which can be called with either no arguments or one argument. List operations which return a new sequence attempt to create an instance of the actual implementation class. To do so, it assumes that the constructor can be called with a single parameter, which is a sequence object used as a data source. If a derived class does not wish to comply with this requirement, all of the special methods supported by this class will need to be overridden; please consult the sources for information about the methods which need to be provided in that case. Changed in version 2.0: Python versions 1.5.2 and 1.6 also required that the constructor be callable with no parameters, and offer a mutable data attribute. Earlier versions of Python did not attempt to create instances of the derived class. UserString — Class wrapper for string objects¶Note This UserString class from this module is available for backward compatibility only. If you are writing code that does not need to work with versions of Python earlier than Python 2.2, please consider subclassing directly from the built-in str type instead of using UserString (there is no built-in equivalent to MutableString). This module defines a class that acts as a wrapper around string objects. It is a useful base class for your own string-like classes, which can inherit from them and override existing methods or add new ones. In this way one can add new behaviors to strings. It should be noted that these classes are highly inefficient compared to real string or Unicode objects; this is especially the case for MutableString. The UserString module defines the following classes:
In addition to supporting the methods and operations of string and Unicode objects (see section String Methods), UserString instances provide the following attribute:
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