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Catching exceptions

Before you start writing your own custom exceptions, let's make sure you have the fundamentals of handling exceptions down.

In this exercise, you are given a function invert_at_index(x, ind) that takes two arguments, a list x and an index ind, and inverts the element of the list at that index. For example invert_at_index([5,6,7], 0) returns 1/5, or 0.2 .

Your goal is to implement error-handling to raise custom exceptions based on the type of error that occurs.

This exercise is part of the course

Introduction to Object-Oriented Programming in Python

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Exercise instructions

Use a try - except - except pattern (with two except blocks) inside the function to catch and handle two exceptions as follows:

  • try executing the code as-is, returning 1/x[ind].
  • if ZeroDivisionError occurs, print "Cannot divide by zero!",
  • if IndexError occurs, print "Index out of range!"

You know you got it right if the code runs without errors, and the output in the console is:

0.16666666666666666
Cannot divide by zero!
None
Index out of range!
None

Hands-on interactive exercise

Have a go at this exercise by completing this sample code.

# Modify the function to catch exceptions
def invert_at_index(x, ind):
  ____:
    return 1/x[ind]
  _____:
    print("____")
  ____:
    print("____")
 
a_list = [5,6,0,7]

# Works okay
print(invert_at_index(a_list, 1))

# Potential ZeroDivisionError
print(invert_at_index(a_list, 2))

# Potential IndexError
print(invert_at_index(a_list, 5))
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