Input & Output

Most useful programs talk to a person: they ask a question, wait for an answer and show a result. In Python, print() sends output to the screen and input() reads what the user types.

In this lesson you will control exactly how print() lays out its output, read input from the keyboard, turn that input into numbers, and stop your program from crashing when someone types something unexpected.

Printing output

You have already used print(). It can take several values separated by commas, and it puts a space between them and a new line at the end.

team = "Kochi Tuskers"
runs = 186
overs = 20

print(team, "scored", runs, "in", overs, "overs")
print("Run rate:", runs / overs)

Kochi Tuskers scored 186 in 20 overs
Run rate: 9.3

Notice that print() accepts numbers directly when you separate values with commas. You do not need str() here.

Changing the separator and the line ending

print() has two useful options, called keyword arguments because you pass them by name:

• sep sets what goes between the values. The default is one space.
• end sets what goes after the last value. The default is a new line, written "\n".

print("12", "08", "2026", sep="-")
print("Loading", end="")
print("...", end=" ")
print("done")
print("Aarav", "Meera", "Kabir", sep=", ")

12-08-2026
Loading... done
Aarav, Meera, Kabir

Because the second and third print() calls change end, they do not move to a new line, so "Loading", "..." and "done" end up on the same line. You will learn more ways to pass arguments in Function Arguments.

Reading input with input()

input() shows a message, called a prompt, then waits until the user types something and presses Enter. It gives back what they typed as a string.

name = input("What is your name? ")
city = input("Which city are you from? ")
print(f"Hello {name}, greetings to everyone in {city}!")

When you run this on this site, the browser opens a small box for each question. In a terminal, it looks like this (the text after each ? is what the user typed):

What is your name? Ananya
Which city are you from? Kochi
Hello Ananya, greetings to everyone in Kochi!

End the prompt with a space, as in "What is your name? ", otherwise the answer is typed right against the question mark.

input() always returns a string

This is the most important fact in this lesson. Even if the user types 21, input() gives you the string "21", not the number 21. To do maths, convert it with int() for whole numbers or float() for decimals.

age = int(input("Your age: "))
height = float(input("Your height in metres: "))

print("In five years you will be", age + 5)
print("Your height in cm is", height * 100)

Your age: 21
Your height in metres: 1.68
In five years you will be 26
Your height in cm is 168.0

Wrapping input() inside int() converts the answer straight away. Without int(), the line age + 5 would fail with TypeError: can only concatenate str (not "int") to str, because Python cannot add a number to text.

Several values on one line

Sometimes it is easier to type several values at once, such as 85 90 78. The string method split() breaks text at the spaces and gives you a list of pieces:

answer = input("Enter marks in three subjects: ")
parts = answer.split()

maths = int(parts[0])
science = int(parts[1])
english = int(parts[2])

total = maths + science + english
print("Total:", total, "out of 300")

Enter marks in three subjects: 85 90 78
Total: 253 out of 300

parts is a list such as ["85", "90", "78"]. Each piece is still a string, so each one goes through int(). You will learn neater ways to convert a whole list in Comprehensions and more about split() in String Methods.

Handling bad input

People make typing mistakes. If someone types twenty when you call int(), the program stops with ValueError: invalid literal for int() with base 10: 'twenty'. You can check the text first: the string method isdigit() is True only when every character is a digit.

text = input("How many tickets? ").strip()

if text.isdigit():
    tickets = int(text)
    print("Amount to pay: ₹", tickets * 150)
else:
    print("Please type a whole number, like 2.")

How many tickets? two
Please type a whole number, like 2.

strip() removes spaces the user may have typed by accident. The if and else choose what to do; they are explained in if, elif & else. The professional way to handle bad input is try and except, which you will learn in Errors & Exceptions.

Common mistakes

• Doing maths on input directly. input("Age: ") + 1 fails. Convert first: int(input("Age: ")) + 1.
• Using int() for decimal input. int("4.5") fails. Use float() when the user may type a decimal point.
• Forgetting the space in the prompt. input("Name:") makes the answer touch the colon. Add a space at the end.
• Joining numbers with + in print(). print("Total: " + total) fails when total is a number. Use a comma, or an f-string: print(f"Total: {total}").

Key points

• print() shows values separated by a space and ends with a new line.
• sep changes the separator and end changes the line ending.
• input("prompt ") shows a prompt and returns what the user typed.
• input() always returns a string; use int() or float() to get a number.
• split() breaks a line of input into a list of strings.
• Check input with methods like isdigit() before converting; later you will use try and except.

CUP_PRICE = 15

name = input("Your name: ").strip()
cups_text = input("How many cups? ").strip()

if cups_text.isdigit():
    cups = int(cups_text)
    print(f"Bill for {name}: {cups} cups x ₹{CUP_PRICE} = ₹{cups * CUP_PRICE}")
else:
    print("Sorry, please enter the number of cups as digits.")