Try, Except, Else, Finally in Python

with 3 examples per block and detailed explanation — same format and style:

Try, Except, Else, Finally in Python

Python provides a structured way to handle exceptions using four keywords:

try — Code block where exceptions can occur except — Code block to handle exceptions else — Runs if no exception occurs finally — Runs always (used for cleanup)

This helps you write robust, error-tolerant programs.

Basic Syntax

try:
    # Code that may raise an exception
except ExceptionType:
    # Code that runs if exception occurs
else:
    # Runs if no exception occurs
finally:
    # Always runs (cleanup)

Example 1: Try-Except Block

try:
    num = int(input("Enter a number: "))
    print("Result:", 10 / num)
except ZeroDivisionError:
    print("Error: Division by zero!")
except ValueError:
    print("Error: Invalid input!")

# If input = 0
Error: Division by zero!
 
# If input = abc
Error: Invalid input!

Explanation: try block attempts to execute code. If an exception occurs — corresponding except block handles it.

Example 2: Try-Except with Generic Exception

try:
    file = open("nonexistent.txt")
except Exception as e:
    print("An error occurred:", e)

An error occurred: [Errno 2] No such file or directory: 'nonexistent.txt'

Example 3: Multiple Except Blocks

try:
    lst = [1, 2, 3]
    print(lst[5])
except IndexError:
    print("Index out of range!")
except Exception as e:
    print("Some other error:", e)

Index out of range!

Example 4: Using Else Block

try:
    x = 5
    y = 2
    result = x / y
except ZeroDivisionError:
    print("Cannot divide by zero.")
else:
    print("Result is:", result)

Result is: 2.5

Explanation: else runs only if no exception occurs.

Example 5: Try-Except-Else-Finally

try:
    value = int("100")
except ValueError:
    print("Invalid value.")
else:
    print("Conversion successful. Value =", value)
finally:
    print("Execution completed.")

Conversion successful. Value = 100
Execution completed.

Explanation: finally block always runs — even if an exception is raised. Useful for cleanup — closing files, releasing resources, etc.

Example 6: Using Finally for Cleanup

try:
    file = open("sample.txt", "w")
    file.write("Hello, Python!")
except IOError:
    print("I/O error occurred.")
else:
    print("File written successfully.")
finally:
    file.close()
    print("File closed.")

File written successfully.
File closed.

Key Points

try: Code that may raise an exception except: Catches and handles exceptions else: Runs if no exception occurred finally: Always runs (useful for resource cleanup)

Summary

• Python provides structured exception handling with try, except, else, finally.
• Helps manage runtime errors gracefully.
• Allows performing safe cleanup of resources.
• Always close files or release resources inside finally.

Next, we will cover Raising Exceptions — how you can manually trigger exceptions in your code for better error handling.