GNU Info

(python2.1-lib.info)UserString

---

Next: operator Prev: UserList Up: Python Runtime Services

---

Enter node , (file) or (file)node

Class wrapper for string objects
================================

Class wrapper for string objects.  This module was written by Peter
Funk <pf@artcom-gmbh.de>.
This manual section was written by Peter Funk <pf@artcom-gmbh.de>.
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:

`UserString([sequence])'
     Class that simulates a string or a Unicode string object.  The
     instance's content is kept in a regular string or Unicode string
     object, which is accessible via the `data' attribute of
     `UserString' instances.  The instance's contents are initially set
     to a copy of SEQUENCE.  SEQUENCE can be either a regular Python
     string or Unicode string, an instance of `UserString' (or a
     subclass) or an arbitrary sequence which can be converted into a
     string using the built-in `str()' function.

`MutableString([sequence])'
     This class is derived from the `UserString' above and redefines
     strings to be _mutable_.  Mutable strings can't be used as
     dictionary keys, because dictionaries require _immutable_ objects
     as keys.  The main intention of this class is to serve as an
     educational example for inheritance and necessity to remove
     (override) the `__hash__()' method in order to trap attempts to
     use a mutable object as dictionary key, which would be otherwise
     very error prone and hard to track down.

In addition to supporting the methods and operations of string and
Unicode objects (see section Note: String Methods, "String Methods"),
`UserString' instances provide the following attribute:

`data'
     A real Python string or Unicode object used to store the content
     of the `UserString' class.