Input and Output

Programs talk to the user in two ways: output (showing results with print()) and input (reading data with input()). Together they make a program interactive.

Output with print()

You already know print(). It can print text, variables, and several items separated by commas.

name = "Aman"
print("Hello", name, "welcome!")

Input with input()

input() pauses the program and waits for the user to type. It always returns a string — convert it with int() or float() for numbers.

Program 1: Greet the User

name = input("What is your name? ")
print("Nice to meet you,", name)

input("What is your name? ") shows the prompt and stores the typed text in name.

Program 2: Sum of Two Numbers

a = int(input("First number : "))
b = int(input("Second number: "))
total = a + b
print("Sum =", total)

• int(input(...)) reads text and converts to integer in one step.
• Without int(), a + b would join the strings instead of adding.

Program 3: Simple Interest

p = float(input("Principal: "))
r = float(input("Rate %: "))
t = float(input("Time (years): "))

si = (p * r * t) / 100
print("Simple Interest =", si)

We use float() here because rate and time can have decimals.

f-strings (Modern Formatting)

The cleanest way to mix text and variables is an f-string — put f before the quote and variables inside { }.

name = "Aman"
marks = 95
print(f"{name} scored {marks} marks")

Common Mistakes

• Forgetting to convert input() with int()/float().
• Adding two inputs and getting joined text instead of a sum.
• Missing the space at the end of the prompt text.

Practice Tasks

1. Ask the user's age and print the year they were born.
2. Read three subject marks and print the total and average.
3. Ask for a temperature in Celsius and print it in Fahrenheit.

Summary

• print() shows output; input() reads input.
• input() always returns a string — convert for maths.
• f-strings (f"{var}") are the cleanest way to format output.