Python Basic Input and Output

Input and Output

In Python, you can interact with users using the input() and print() functions.

1. Using print() – Displaying Output

Let’s start by displaying something to the screen. The print() function sends information from your program to the user.

print("Hello, World!")

Hello, World!

What’s Happening?

Python simply prints the string "Hello, World!" to the console. This is your first output.

Printing Multiple Values

You can print more than one item by separating them with commas:

name = "Arjun"
age = 25
print("Name:", name, "Age:", age)

Name: Arjun Age: 25

Explanation

Each argument is converted to a string if needed, and Python automatically inserts spaces between them. You don’t need to manually add spaces unless you want specific formatting.

2. Using input() – Getting User Input

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

name = input("What is your name? ")
print("Hello", name)

What is your name? Arjun
Hello Arjun

Important Notes:

• input() always returns a string. Even if you type numbers, Python treats them as strings.
• Use type() to check the data type if you're unsure.

Type Conversion (Casting)

To convert user input to another type (like integer or float), use casting functions:

age = input("Enter your age: ")
print("Type before conversion:", type(age))

age = int(age)
print("Type after conversion:", type(age))

Enter your age: 20
Type before conversion: <class 'str'>
Type after conversion: <class 'int'>

Verifying and Validating Input

Always check and validate user input to prevent errors. Here's a basic numeric check:

user_input = input("Enter a number: ")

if user_input.isdigit():
    number = int(user_input)
    print("You entered:", number)
else:
    print("That’s not a valid number.")

Enter a number: 45
You entered: 45

Enter a number: hello
That’s not a valid number.

Tips

• print() is for output. Use sep and end to customize formatting.
• input() is for input. It always returns a string.
• Use int(), float(), or str() to convert types as needed.
• Always validate user input to avoid runtime errors.