User Input and Print

Introduction

Programs often need to communicate with the person running them — either by displaying output or asking for input. This section covers the print() function in more detail and introduces input() for reading user input.

print() in Depth

print() can take multiple arguments and has optional keyword arguments to control formatting.

print("Hello", "World")           # Hello World
print("Hello", "World", sep="-")  # Hello-World
print("Loading", end="...")       # Loading... (no newline)
print("done")                     # done

Formatting numbers

salary = 75234.5678
print(f"Salary: {salary:.2f}")    # Salary: 75234.57
print(f"Salary: {salary:,.2f}")   # Salary: 75,234.57

input()

input() pauses the program and waits for the user to type something and press Enter. It always returns a string.

Syntax

variable = input("Prompt message: ")

Example

name = input("Enter your name: ")
print(f"Hello, {name}!")

Enter your name: Alice
Hello, Alice!

input() Always Returns a String

If you need a number from the user, you must convert it.

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

Or on one line:

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

If the user types something that cannot be converted (e.g. "hello" when you call int()), Python will raise a ValueError. Error handling is covered in Grade 6.

Combining input() and print()

firstname = input("First name: ")
lastname = input("Last name: ")
salary = float(input("Salary: "))

print(f"\nEmployee Summary")
print(f"Name:   {firstname} {lastname}")
print(f"Salary: £{salary:,.2f}")

First name: Alice
Last name: Smith
Salary: 75000

Employee Summary
Name:   Alice Smith
Salary: £75,000.00

Practice Exercises

• Ask the user for their name and favourite number. Print a sentence using both.
• Ask the user for two numbers. Add them together and print the result.
• Print a formatted receipt: ask for an item name and price, then print them aligned neatly using an f-string.
• Ask the user for their year of birth. Calculate and print their approximate age.