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Exception Handling Syntax

Python uses try–except blocks to handle runtime exceptions and prevent application crashes.

Basic try–except Syntax

try:
    # risky code
except ErrorType:
    # handling code

Code inside try is monitored for errors
If an exception occurs, Python jumps to the matching except block

Example: Handling Division by Zero

a = 5
b = 0

try:
    result = a / b
    print("Result is:", result)
except Exception:
    print("An error occurred: Division by zero is not allowed")

print("End of execution")

Output

An error occurred: Division by zero is not allowed
End of execution

Application does not crash
Remaining code executes normally

Handling Multiple Exceptions

Different errors require different handling logic.

Example

try:
    a = int(input("Enter numerator: "))
    b = int(input("Enter denominator: "))
    result = a / b
    print("Result is:", result)

except ZeroDivisionError as zde:
    print("Division by zero is not allowed.", zde)

except ValueError as ve:
    print("Invalid input. Please enter numeric values.", ve)

except Exception as e:
    print("An unexpected error occurred.", e)

print("End of execution")

Sample Outputs

Case 1: Zero Division

Enter numerator: 4
Enter denominator: 0
Division by zero is not allowed. division by zero
End of execution

Case 2: Invalid Input

Enter numerator: 4
Enter denominator: t
Invalid input. Please enter numeric values. invalid literal for int()
End of execution

Multiple_Except_Blocks

Python Exception Hierarchy

Python exceptions follow a hierarchical structure.

Exception Hierarchy Diagram

BaseException
│
├── SystemExit
├── KeyboardInterrupt
│
└── Exception
    ├── ArithmeticError
    │   └── ZeroDivisionError
    ├── ValueError
    ├── TypeError
    ├── IndexError
    └── FileNotFoundError

Why Hierarchy Matters?

Parent exceptions catch child exceptions
Use specific exceptions first
Use generic Exception as a fallback

Summary

Python uses try–except blocks to handle runtime exceptions and prevent application crashes.
Code inside the try block is monitored, and matching except blocks handle specific errors.
Multiple except blocks allow handling different exception types with customized messages.
Python exceptions follow a hierarchical structure, where parent exceptions can catch child exceptions.
Always handle specific exceptions first and use Exception as a fallback for unexpected errors.

Written By: Muskan Garg

try-except And Exceptional Hierarchy