Catching exceptions

Before you start writing your own custom exceptions, let's make sure you have the basics 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], 1) returns 1/6, or 0.166666 .

Try running the code as-is and examine the output in the console. There are two unsafe operations in this function: first, if the element that we're trying to invert has the value 0, then the code will cause a ZeroDivisionError exception. Second, if the index passed to the function is out of range for the list, the code will cause a IndexError. In both cases, the script will be interrupted, which might not be desirable.

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,
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

Exercise

Catching exceptions

Instructions