Lab 8

Exceptions and testing

CS1302 Introduction to computer programming

Motivation of handling exception

When will the exception occur?

DevisioinByZeroError

IndexError

It is tedious and time-consuming to debug if the structure of the program is perplexing

What are exceptions?

An exception is a special object that the program can create when it encounters an extraordinary situation, usually some sort of run-time error. 

Common exceptional situations:

• Attempting to read past the end of a file

• Convert a non-numeric string to a number

• A sequence(list,tuple) Index is out of range

Two ways of handling

First: look before you leap

Second: easier to ask for forgiveness than permission

Pros&Cons of two approaches

LPYL

• Not robust
• Difficult to implement

EAFP

• Robust
• Easy to implement

Basic structure of handling exception

Why do we need the finally block? 

Execution flow of the try/except statement

Handling mulitiple exceptions

Why we need to handle mutliple excpetions?

Raising Exceptions

Meaning of creating your own excpeiton?

Using Exceptions wisely

Is the use of exception necessary?