Question

Is there something like _if_ or _not_ methods implemented in a customized class? So when I instantiate a new class, I can use

if myobject:
    return True

or

if not myobject:
    return False

Answer 1

If what you want is to use instances of your class as boolean values, i.e., some of the instances of your class are truthy and some are falsy, then, in your class, define __nonzero__ appropriately.

See Section 5.1 in the docs

By default, saying

if myobject:

where myobject is an instance of some class, will evaluate as if you wrote

if True:

Defining __nonzero__() allows you customize how your objects are used in a boolean context (so to speak).

For Python 3, things are a little different. See this SO question.