Choisissez la catégorie, puis la rubrique :

5.13 UserList -- Class wrapper for list objects

5.13 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:

class UserList( [list])
Class that simulates a list. The instance's contents are kept in a regular list, which is accessible via the data attribute of UserList instances. The instance's contents are initially set to a copy of list, defaulting to the empty list []. list can be either a regular Python list, or an instance of UserList (or a subclass).

In addition to supporting the methods and operations of mutable sequences (see section 3.6), UserList instances provide the following attribute:

A real Python list object used to store the contents of the UserList class.

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.

See About this document... for information on suggesting changes.
Quels sont les frameworks que vous aimeriez apprendre en 2019 ?
Éducation : Python deviendra le langage officiel de programmation en France, dans le cadre de la réforme du Bac et du lycée
Quel langage de programmation comporte le plus de vulnérabilités en matière de sécurité ?
Introduction à la bibliothèque Pandas - Analyse de données en Python, un tutoriel de Gabor Laszlo Hajba traduit par l'équipe de rédaction
Contacter le responsable de la rubrique Python

Partenaire : Hébergement Web