I/O and Error Handling

Getting User Input

The input() function is the standard way to get input from the user in the console. It pauses the program and waits for the user to type something and press Enter. Important: input() always returns the user\'s input as a string, even if they type numbers.

username = input("Enter your name: ")print("Hello, " + username)
# You must cast the input if you want to treat it as a numberage_str = input("Enter your age: ")age = int(age_str)print(f"You will be {age + 1} next year.")

Formatting Output with F-Strings

While you can concatenate strings with +, a more powerful and readable way to format strings is with F-strings (formatted string literals). You prefix the string with an f and place your variables directly inside curly braces {}.

name = "Alice"item_count = 5total_price = 75.5
# F-string (recommended)print(f"Hello, {name}! You have {item_count} items in your cart.")# You can even format numbers!print(f"The total price is ${total_price:.2f}.")

The try...except Block

Errors, called exceptions in Python, will stop your program if not handled. The try...except block is Python\'s way of handling these exceptions gracefully.

1. The code inside the try block is executed first.
2. If an error occurs in the try block, Python looks for a matching except block and executes its code.
3. If no error occurs, the except block is skipped.
4. The else block is optional and runs only if no exceptions were raised in the try block.
5. The finally block is also optional and runs no matter what, whether an exception occurred or not. It\'s often used for cleanup operations.

try:  num_str = input("Enter a number: ")  num = int(num_str)  result = 100 / numexcept ValueError:  print("That was not a valid number!")except ZeroDivisionError:  print("You can\'t divide by zero!")except Exception as e:  print(f"An unexpected error occurred: {e}")else:  print(f"100 divided by {num} is {result}.")finally:  print("Execution finished.")