Input & Output

Every useful program does two things — it shows information to the user, and it receives information from the user. In Python, this is done with two built-in functions: print() for output and input() for input.

print() — displaying output

print() sends text to the screen. You will use this constantly — for showing results, debugging, and communicating with the user.

print("Hello, world!")   # Hello, world!
print(42)                # 42
print(True)              # True

You can print multiple values at once by separating them with commas. Python adds a space between them automatically:

name = "Ali"
age = 22

print(name, age)          # Ali 22
print("Name:", name)      # Name: Ali
print("Age:", age)        # Age: 22

Changing the separator

By default, print() puts a space between values. You can change this with the sep argument:

print("Ali", "Ahmed", "Khan")              # Ali Ahmed Khan
print("Ali", "Ahmed", "Khan", sep="-")     # Ali-Ahmed-Khan
print("Ali", "Ahmed", "Khan", sep="")      # AliAhmedKhan

Changing the end character

By default, print() adds a newline at the end — so each print starts on a new line. You can change this with the end argument:

print("Loading", end="")
print("...")
# Loading...

print("one", end=" ")
print("two", end=" ")
print("three")
# one two three

Formatting output

Printing raw variables works, but often you want to build a proper message. Python gives you a few ways to do this.

f-strings (recommended)

f-strings are the modern, cleanest way to format strings. Put an f before the opening quote, then wrap variable names in {}:

name = "Ali"
age = 22

print(f"My name is {name} and I am {age} years old.")
# My name is Ali and I am 22 years old.

You can put any expression inside the curly braces — not just variable names:

a = 10
b = 3

print(f"{a} + {b} = {a + b}")       # 10 + 3 = 13
print(f"{a} divided by {b} = {a / b:.2f}")   # 10 divided by 3 = 3.33

The :.2f part means "show this float with 2 decimal places". You will see more formatting options like this as you go.

.format() method

An older but still valid approach:

name = "Ali"
age = 22

print("My name is {} and I am {} years old.".format(name, age))
# My name is Ali and I am 22 years old.

String concatenation

You can join strings together with +. But every value must be a string — numbers need to be converted first:

name = "Ali"
age = 22

print("My name is " + name)                    # My name is Ali
print("I am " + str(age) + " years old.")      # I am 22 years old.

input() — getting input from the user

input() pauses the program and waits for the user to type something and press Enter. Whatever they type is returned as a string.

name = input("What is your name? ")
print(f"Hello, {name}!")

When this runs:

What is your name? Ali
Hello, Ali!

The string you pass to input() is the prompt — the message shown to the user before they type. It is optional, but always include it so the user knows what to enter.

input() always returns a string

This is the most important thing to understand about input(). No matter what the user types — a number, a decimal, anything — it comes back as a string.

age = input("Enter your age: ")
print(type(age))   # <class 'str'>

If you want to do math with the input, you must convert it first:

age = input("Enter your age: ")
age = int(age)

print(f"In 10 years you will be {age + 10}.")

Or on one line:

age = int(input("Enter your age: "))
print(f"In 10 years you will be {age + 10}.")

A simple example putting it together

name = input("Enter your name: ")
age = int(input("Enter your age: "))

print(f"Hello, {name}!")
print(f"You were born around {2024 - age}.")

Output:

Enter your name: Ali
Enter your age: 22
Hello, Ali!
You were born around 2002.

Summary