User Input and Output

Interaction is what makes a program useful. In Python, we use two primary functions to talk to the user: print() for output and input() for input.

1. Output with print()

The print() function sends data to the screen. You can print multiple items at once and even format them elegantly.

• Comma Separation: Automatically adds a space between items.

• F-Strings (Formatted Strings): The modern way to inject variables into text using {}.

2. Input with input()

The input() function pauses the program and waits for the user to type something.

Crucial Rule: input() always treats everything as a String. If you want to do math with a user's input, you must convert it using int() or float().

# --- OUTPUT ---
name = "Alice"
version = 3.12

# Using an f-string (the most popular way)
print(f"Hello {name}, you are using Python {version}")

# --- INPUT ---
# Getting a string
user_city = input("Where do you live? ")

# Getting a number (Casting is required!)
age_str = input("How old are you? ")
age = int(age_str)  # Convert string to integer

print(f"In 5 years, you will be {age + 5} years old in {user_city}!")