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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.