Learn

The exception handlers from the previous exercise handled any exception hit during the try clause. However, in most cases, we will have an idea of the types of exceptions that might occur within our code. It is generally considered best practice to be as specific as possible with the exceptions we want to raise unless there is a specific reason for catching any type of exception.

We can catch a specific exception by listing it after the except keyword, as in the example below:

try: print(undefined_var) except NameError: print('We hit a NameError')

In this case, the except block is only executed if a NameError is encountered (in the try block) rather than any exception. If any other exception occurs, it is unhandled, and the program terminates.

When we specify exception types, Python also allows us to capture the exception object using the as keyword. The exception object hosts information about the specific error that occurred. Examine our previous function but now capturing the exception object as errorObject:

try: print(undefined_var) except NameError as errorObject: print('We hit a NameError') print(errorObject)

Would output:

We hit a NameError name 'undefined_var' is not defined

Its worth noting errorObject is an arbitrary name and can be replaced with any name we see fit. The following code would work exactly the same:

try: print(undefined_var) except NameError as e: print('We hit a NameError') print(e)

Let’s get some practice capturing specific exceptions.

Instructions

1.

Let’s improve upon the exception handler we built in the previous exercise.

Change the except clause so that it only handles a ZeroDivisionError. Store the ZeroDivisionError we intend to capture into a variable called e.

2.

Print e as the second print() statement in the except block.

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