Odds and ends

Sometimes it is useful to have a data type similar to the Pascal ``record'' or C ``struct'', bundling together a couple of named data items. An empty class definition will do nicely, e.g.:

        class Employee:
                pass

        john = Employee() # Create an empty employee record

        # Fill the fields of the record
        john.name = 'John Doe'
        john.dept = 'computer lab'
        john.salary = 1000

A piece of Python code that expects a particular abstract data type can often be passed a class that emulates the methods of that data type instead. For instance, if you have a function that formats some data from a file object, you can define a class with methods read() and readline() that gets the data from a string buffer instead, and pass it as an argument. (Unfortunately, this technique has its limitations: a class can't define operations that are accessed by special syntax such as sequence subscripting or arithmetic operators, and assigning such a ``pseudo-file'' to sys.stdin will not cause the interpreter to read further input from it.)

Instance method objects have attributes, too: m.im_self is the object of which the method is an instance, and m.im_func is the function object corresponding to the method.