correctly designed classes provide encapsulation the internal details of an object are hidden inside the class definition so that other portions of the program do not need to know how an object is implemented this separation of concerns is programming convention in pythonthe instance variables of an object should only be accessed or modified through the interface methods of the class most gui systems are built using an object-oriented approach we can build novel gui widgets by defining suitable classes exercises review questions true/false new objects are created by invoking constructor functions that live in objects are called instance variables the first parameter of python method definition is called this an object may have only one instance variable in data processinga collection of information about person or thing is called file in python classthe constructor is called __init__ docstring is the same thing as comment instance variables go away once method terminates method names should always begin with one or two underscores it is considered bad style to directly access an instance variable outside of class definition multiple choice what python reserved word starts class definitionadef bclass cobject d__init__ method definition with four formal parameters is generally called with how many actual parametersathree bfour cfive dit depends method definition is similar to (naloop bmodule cimport statement dfunction definition