Catching Multiple Exceptions in Python

Pre-requisite knowledge -

Python Exception Handling: Try, Except, Else and Finally

An example based guide to handle Python exceptions using try, except, else and finally keywords.

PyleninLenin Mishra

Let’s say, you are trying to print an element of a list through user input. You are using IndexError exception in your except block to make sure, the program doesn’t crash if user inputs an index that doesn’t exist.

Code

x = [1, 2, 3, 4]

while True:
    user_input = input("Guess a position ==> ")
    try:
        print(x[int(user_input)])
        break
    except IndexError as e:
        print(f"Guess a number between {-1*len(x)} and {len(x)-1}")

Now, try to run the above code in your Python IDE. As long as user enters an integer, the code will run fine.

Output - 1

Guess a position ==> 5
Guess a number between -4 and 3
Guess a position ==> -1
4

However, what happens if user enters a float?

Output - 2

Guess a position ==> 3.5
Traceback (most recent call last):
  File "some_file_location", line 6, in <module>
    print(x[int(user_input)])
ValueError: invalid literal for int() with base 10: '3.5'

Now your program has crashed due to a ValueError exception. You hadn’t taken this exception into account.

There are multiple solutions to this problem.

Solution 1 - Multiple except blocks for multiple exceptions

Code

x = [1, 2, 3, 4]

while True:
    user_input = input("Guess a position ==> ")
    try:
        print(x[int(user_input)])
        break
    except IndexError as e:
        print(f"Guess a number between {-1*len(x)} and {len(x)-1}")
    except ValueError as e:
        print("You are only allowed integers")

Output

Guess a position ==> 3.5
You are only allowed integers
Guess a position ==> 10
Guess a number between -4 and 3
Guess a position ==> 1
2

Solution 2 - Catch Multiple Exceptions in a single except block

Code

x = [1, 2, 3, 4]

while True:
    user_input = input("Guess a position ==> ")
    try:
        print(x[int(user_input)])
        break
    except (IndexError, ValueError) as e:
        if e.__class__.__name__ == 'IndexError':
            print(f"Guess a number between {-1 * len(x)} and {len(x) - 1}")
        elif e.__class__.__name__ == 'ValueError':
            print("You are only allowed integers")
        else:
            print(f"Error occured - {e}")

Output

Guess a position ==> 10
Guess a number between -4 and 3
Guess a position ==> 1.5
You are only allowed integers
Guess a position ==> 2
3

Solution 3 - Use the base Exception class

Code

x = [1, 2, 3, 4]

while True:
    user_input = input("Guess a position ==> ")
    try:
        print(x[int(user_input)])
        break
    except Exception as e:
        if e.__class__.__name__ == 'IndexError':
            print(f"Guess a number between {-1 * len(x)} and {len(x) - 1}")
        elif e.__class__.__name__ == 'ValueError':
            print("You are only allowed integers")
        else:
            print(f"Error occured - {e}")

Output

Guess a position ==> 10
Guess a number between -4 and 3
Guess a position ==> 3.5
You are only allowed integers
Guess a position ==> "1"
You are only allowed integers
Guess a position ==> 2
3