Errors are inevitable in programming. But with Python’s try-except blocks, you can gracefully handle exceptions and make your programs more robust, user-friendly, and crash-resistant.

This guide explains:

• What exceptions are

• How try-except works

• Common exception types

• Advanced usage (else, finally)

• Real-world examples

• Tips and common pitfalls

What Is an Exception?

An exception is an error that occurs during the execution of a program, disrupting its normal flow.

Example:

print(10 / 0)

Output:

ZeroDivisionError: division by zero

This stops the program. But what if we could handle it smoothly?

Basic Syntax of try-except

try:
    # Code that might throw an error
except SomeException:
    # Code to run if an error occurs

Example:

try:
    result = 10 / 0
except ZeroDivisionError:
    print("You can't divide by zero!")

Output:

You can't divide by zero!

Catching Multiple Exceptions

You can handle multiple specific exceptions:

try:
    value = int("abc")
except ValueError:
    print("Invalid input: not an integer")

Or handle several at once:

try:
    risky_code()
except (ValueError, ZeroDivisionError):
    print("Something went wrong with input or math.")

Catching All Exceptions (Use with Caution)

try:
    unknown_function()
except Exception as e:
    print(f"An error occurred: {e}")

• ✅ Good for logging or debugging

• ⚠️ Not recommended for silent failure or production masking

✅ Using else with try

The else block runs only if no exception was raised.

try:
    number = int("42")
except ValueError:
    print("Conversion failed")
else:
    print("Conversion successful:", number)

Using finally for Cleanup

The finally block always executes, whether or not an exception occurred. It’s useful for resource cleanup like closing files or database connections.

try:
    file = open("data.txt", "r")
    content = file.read()
except FileNotFoundError:
    print("File not found!")
finally:
    print("Closing file (if open)")
    if 'file' in locals():
        file.close()

Common Python Exceptions

Real-World Example: Safe Input and Division

def safe_divide():
    try:
        a = int(input("Enter numerator: "))
        b = int(input("Enter denominator: "))
        result = a / b
    except ValueError:
        print("Please enter valid integers.")
    except ZeroDivisionError:
        print("Denominator cannot be zero.")
    else:
        print(f"Result: {result}")
    finally:
        print("Operation complete.")

safe_divide()

⚠️ Common Pitfalls

Tips

✅ Use try-except to handle expected errors (e.g., user input, file access)
✅ Always catch specific exceptions first, then general ones
✅ Log errors during development or in production environments
✅ Use else for code that should only run if no error occurred
✅ Use finally for guaranteed clean-up, even if an exception occurs

Complete Code Example

def process_file(filename):
    try:
        file = open(filename, "r")
        content = file.read()
    except FileNotFoundError:
        print(f"Error: File '{filename}' does not exist.")
    except PermissionError:
        print(f"Error: Permission denied for file '{filename}'.")
    else:
        print("File read successfully:")
        print(content)
    finally:
        if 'file' in locals():
            file.close()
            print("File closed.")

# Try with an existing and a non-existing file
process_file("example.txt")

Conclusion

Python’s try-except blocks are essential for writing reliable code. By anticipating errors and handling them appropriately, you can make your applications more robust, user-friendly, and maintainable.

Learn to use try, except, else, and finally strategically, and you’ll have the tools to handle almost anything Python throws at you.