Question

Python

1.Explain what happens when a program receives a non-numeric string when a number is expected as input, and explain how the try-except statement can be of use in this situation.

2.What is meant by the state of an object, and how does the programmer access and manipulate it?

3.Explain the differences between instance variables and temporary variables. Focus on their visibility in a class definition, and on their roles in managing data for an object of that class.

4.Explain the purpose of the variable self in a Python class definition.

Answer 1

Ans1:

• In lots of Python programs we want to interact with the end-user by asking questions and retrieving user inputs from the user.In order to do so we generally use input() function.
• We also have some cases in which we need to find numbers like whole numbers in order to achieve that we need to convert user input into integer using int() function.
• But in the above case if the users provide non-numeric values then the conversion will fail using above method and exception will be generated and the program will stop running.
• So, in order to validate the user entry and ensure that it is a numeric, we can use use try-except function.
• The try block helps us to test the block of code for errors and the except block is used to handle the errors and finally block helps us to execute code, without depending on the result of try-except block.
• For the above scenario try-except can be used like it will go on asking the user to provide a valid input then only the program can be executed.

Ans2:

• State of an object have an hold within the static properties of the object including the current values of each of these properties .

• Basically state of an object provides us the information about the type or value of that object. For example We have object called car and its state is colour,engine,wheels.
• Programmers can easily modify the state of objects as Object oriented Programming has provided the feature of data encapsulation which means the act of representing essential features without showing background details
• It tells that if any programmer has created an object then a new programmer can modify it but former programmer features still remain intact as new programmer only sees the outside details not the internal details .

Ans 3:

Instance Variables:-

• They are declared in class but outside the method, constructor or block
• The created when an object is created using the keyword ‘new’ and is destroyed when object is destroyed.
• They can be accessed by calling the variable name inside class.
• They hold values that are being referenced by one or more method,constructor or block

Temporary variables:-

• They are represented as instances in order to call method or chain of methods.
• They are immediately destroyed after invoking the call.
• They are just used to invoke call method.
• The values acquired by them are stored in variable rather than class interface.

Ans4:

• The variable self represents the instance of the class.
• When we use the “self” keyword we are able to access the attributes and methods of the class in python.
• It helps to binds the attributes with the given arguments.
• The most important reason we need to use self is because Python does not use the @ syntax to refer to instance attributes.
• It helps to increase the readability of code.