1.2 Input/output

Input and output functions let Python programs communicate with users and move data through a program. They allow you to display information, collect user input, and convert data types for calculations.

The two main tools here are print() for output and input() for user input. Once you can customize output, store input, and convert data types, you can build more interactive programs.

Input and Output Functions

Custom output with print()

• print() displays output to the console (stdout)
• Separates arguments with a space by default and ends with a newline character
• Customize the separator using the sep parameter
  • print("Hello", "world", sep="-") outputs "Hello-world"
• Customize the line ending using the end parameter
  • print("Hello", end="") outputs "Hello" without a newline
  • print("Hello", end=" ") outputs "Hello " with a space instead of a newline
• Use escape characters to include special characters
  • \n for newline, \t for tab
  • print("Hello\nworld") outputs "Hello" on one line and "world" on the next

User input and variable storage

• input() gets input from the user via the console (stdin)
• Prompts the user to enter a value and waits for input
• Returns the user's input as a string
• Assign the result of input() to a variable to store the user's input
  • name = input("Enter your name: ") prompts the user and stores the input in name
• Provide a prompt message as an argument to guide the user
  • Displayed before the user enters their input
  • age = input("Enter your age: ") prompts with "Enter your age: "

Data type conversion for calculations

• User input is always returned as a string by input()
• Convert the input to the appropriate data type for numerical operations
  • int() converts input to an integer
    • num = int(input("Enter a number: ")) converts input to integer and stores in num
  • float() converts input to a floating-point number
    • price = float(input("Enter the price: ")) converts input to float and stores in price
• Attempting numerical operations on strings will result in a TypeError
  • result = "10" + 5 raises an error (cannot add string and integer)
• Handle invalid input by catching exceptions with a try-except block
  • Catch ValueError exceptions when converting input to numerical data types
  • Example:

    </>Python
    try:
        age = int(input("Enter your age: "))
    except ValueError:
        print("Invalid input. Please enter a valid integer.")

Advanced I/O Operations

• File I/O allows reading from and writing to files on the system
• Buffering can improve performance by reducing the number of I/O operations
• Formatting options enable precise control over output appearance