Multiple exception handling in Python

Introduction

Sometimes, a program can have different kinds of errors. Multiple exception handling helps us catch and fix each type separately.

When you want to handle different errors in different ways.

When your program might fail for several reasons and you want clear messages for each.

When you want to keep your program running even if one part causes an error.

When debugging to know exactly what kind of error happened.

Syntax

Python

try:
    # code that might cause an error
except ExceptionType1:
    # handle ExceptionType1
except ExceptionType2:
    # handle ExceptionType2
except ExceptionType3 as e:
    # handle ExceptionType3 and use variable e
else:
    # code if no exception happens
finally:
    # code that runs no matter what

You can have many except blocks after one try.

The else block runs only if no exceptions happen.

Examples

This code handles two errors: if input is not a number, or if dividing by zero.

Python

try:
    x = int(input('Enter a number: '))
    y = 10 / x
except ValueError:
    print('That was not a number!')
except ZeroDivisionError:
    print('Cannot divide by zero!')

This code handles file errors and always closes the file.

Python

file = None
try:
    file = open('data.txt')
    data = file.read()
except FileNotFoundError:
    print('File not found!')
except IOError:
    print('Error reading file!')
else:
    print('File read successfully')
finally:
    if file:
        file.close()

Sample Program

This program asks for a number, divides 100 by it, and handles two errors separately. It always prints a done message.

Python

try:
    num = int(input('Enter a number: '))
    result = 100 / num
except ValueError:
    print('Oops! That is not a valid number.')
except ZeroDivisionError:
    print('Oops! Cannot divide by zero.')
else:
    print(f'Result is {result}')
finally:
    print('Done with the calculation.')

Important Notes

Order matters: put more specific exceptions before general ones.

Use as e to get the error message if you want to show it.

The finally block runs no matter what, useful for cleanup.

Summary

Multiple exception handling lets you catch different errors separately.

Use multiple except blocks after one try.

Remember else runs if no error, and finally always runs.

Practice

1.

What is the purpose of using multiple except blocks after a single try block in Python?

easy

A. To create multiple loops inside the try block

B. To run the same code multiple times

C. To handle different types of errors separately

D. To ignore all errors silently

Solution

1. Step 1: Understand the role of try-except

   The try block runs code that might cause errors, and except blocks catch those errors.

2. Step 2: Purpose of multiple except blocks

   Multiple except blocks allow catching different error types separately to handle each properly.

3. Final Answer:

   To handle different types of errors separately -> Option C

4. Quick Check:

   Multiple except blocks = handle different errors [OK]

Hint: Multiple except blocks catch different error types separately [OK]

Common Mistakes:

• Thinking multiple except blocks run all at once
• Believing except blocks create loops
• Assuming except blocks ignore errors

2.

Which of the following is the correct syntax to catch both ValueError and TypeError exceptions separately?

try:
    x = int(input())
except ???:
    print("Value error occurred")
except ???:
    print("Type error occurred")

easy

A. except ValueError:
except TypeError:

B. except (ValueError, TypeError):
except Exception:

C. except ValueError, TypeError:
except Exception:

D. except ValueError | TypeError:
except Exception:

Solution

1. Step 1: Check syntax for multiple except blocks

   Each except block must catch one exception type separately using except ExceptionType:.

2. Step 2: Identify correct syntax

   except ValueError: except TypeError: uses separate except blocks for ValueError and TypeError, which is correct syntax.

3. Final Answer:

   except ValueError: except TypeError: -> Option A

4. Quick Check:

   Separate except blocks = except ExceptionType: [OK]

Hint: Use separate except lines for each error type [OK]

Common Mistakes:

• Using commas or pipes inside except incorrectly
• Trying to catch multiple exceptions in one except without tuple
• Using wrong syntax like except ValueError, TypeError:

3.

What will be the output of the following code?

try:
    a = 5 / 0
except ValueError:
    print("Value Error")
except ZeroDivisionError:
    print("Zero Division Error")
else:
    print("No Error")
finally:
    print("Done")

medium

A. Zero Division Error
Done

B. Value Error
Done

C. No Error
Done

D. Zero Division Error

Solution

1. Step 1: Identify the error raised in try block

   The expression 5 / 0 raises a ZeroDivisionError.

2. Step 2: Match the except block and output

   The ZeroDivisionError except block runs, printing "Zero Division Error". The finally block always runs, printing "Done".

3. Final Answer:

   Zero Division Error Done -> Option A

4. Quick Check:

   ZeroDivisionError caught + finally runs = output A [OK]

Hint: Match error type to except block, finally always runs [OK]

Common Mistakes:

• Confusing ValueError with ZeroDivisionError
• Forgetting finally block always runs
• Expecting else block to run on error

4.

Find the error in this code snippet and choose the correct fix:

try:
    x = int('abc')
except ValueError, TypeError:
    print("Error occurred")

medium

A. Change except line to: except ValueError | TypeError:

B. Change except line to: except (ValueError, TypeError):

C. Change except line to: except ValueError, TypeError:

D. No change needed, code is correct

Solution

1. Step 1: Identify syntax error in except line

   The syntax except ValueError, TypeError: is invalid for catching multiple exceptions.

2. Step 2: Correct syntax for multiple exceptions

   Use a tuple of exceptions inside parentheses: except (ValueError, TypeError):.

3. Final Answer:

   Change except line to: except (ValueError, TypeError): -> Option B

4. Quick Check:

   Multiple exceptions need parentheses tuple [OK]

Hint: Use parentheses tuple for multiple exceptions in one except [OK]

Common Mistakes:

• Using commas without parentheses
• Using pipe | operator incorrectly
• Assuming original syntax is valid

5.

You want to write a function that tries to convert a string to an integer and then divide 100 by that number. It should handle ValueError if conversion fails, ZeroDivisionError if division by zero happens, and print "Success" if no error occurs, and print "Done" regardless of errors. Which code correctly implements this?

hard

A. def func(s):
try:
n = int(s)
result = 100 / n
except ValueError:
print("Conversion error")
except ZeroDivisionError:
print("Division by zero")
else:
print("Success")

B. def func(s):
try:
n = int(s)
result = 100 / n
except (ValueError, ZeroDivisionError):
print("Error")
finally:
print("Success")

C. def func(s):
try:
n = int(s)
result = 100 / n
except ValueError:
print("Conversion error")
except ZeroDivisionError:
print("Division by zero")
finally:
print("Success")

D. def func(s):
try:
n = int(s)
result = 100 / n
except ValueError:
print("Conversion error")
except ZeroDivisionError:
print("Division by zero")
else:
print("Success")
finally:
print("Done")

Solution

1. Step 1: Check handling of exceptions and success message

   Function must catch ValueError and ZeroDivisionError separately and print appropriate messages.

2. Step 2: Check use of else and finally blocks

   else runs only if no exception, so "Success" should be printed there. finally always runs, so "Done" can be printed there.

3. Step 3: Verify option correctness

   def func(s): try: n = int(s) result = 100 / n except ValueError: print("Conversion error") except ZeroDivisionError: print("Division by zero") else: print("Success") finally: print("Done") correctly uses separate except blocks, prints "Success" in else, and "Done" in finally.

4. Final Answer:

   Option D code correctly implements all requirements -> Option D

5. Quick Check:

   Separate except + else for success + finally for done [OK]

Hint: Use else for success, finally for cleanup, separate except blocks [OK]

Common Mistakes:

• Printing success in finally instead of else
• Combining exceptions in one except without separate messages
• Omitting finally block when needed