Python Input and Output

1Python Input/Output: overview

Input and output is how a program talks to its user: input() reads a line the user types and returns it as a string, and print() writes text back to the screen.

Before this lesson: Python Variables, Python Data Types, Python Strings

2Python Input/Output: diagram

Quick reference: Python Input/Output

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• Python print() Function — `print(*objects, sep=' ', end='\n')` converts each value to text, joins them with `sep`, writes the result fo…
• Python input() Function — `input(prompt)` shows the prompt, waits for the user to type a line and press Enter, and returns what was typ…

4Python Input/Output: syntax

text = input("Prompt: ")            # always returns a str
whole = int(input("Count: "))       # convert to int
decimal = float(input("Price: "))   # convert to float
print(a, b, sep=", ", end="\n")     # sep between values, end after them
print(f"{price:.2f}")               # exactly two decimal places
print(f"{name:<10}{qty:>5}")        # left / right align in a fixed width

5Python Input/Output: run the example

Press Run (or Ctrl + Enter). The output (step 6) appears directly below the code. Change anything and run it again.

name = input("Your name: ")
tickets = int(input("How many tickets? "))
price = float(input("Price per ticket: "))

total = tickets * price
code = name[:3].upper() + "-" + str(tickets)

print()
print("Booking for", name)
print("Tickets:", tickets, "x", price)
print(f"Total: ${total:.2f}")
print("Booking code:", code)
print("Thank you", name, sep=", ", end="!\n")

Expected outputYour name: Priya
How many tickets? 3
Price per ticket: 12.5

Booking for Priya
Tickets: 3 x 12.5
Total: $37.50
Booking code: PRI-3
Thank you, Priya!

7Python Input/Output: how the example works

Hover or tap a step to highlight its lines in the example above.

1. Line 1input() shows the prompt and waits. The first input line, Priya, comes back as the string "Priya". On this site the typed text appears after the prompt, just like in a terminal.
2. Line 2The second line, 3, arrives as the text "3". int() turns it into the number 3 so it can be used in a calculation.
3. Line 3float() converts the text "12.5" into the decimal number 12.5.
4. Line 53 × 12.5 = 37.5. This only works because both values were converted to numbers first.
5. Line 6String tools from the previous lesson build a booking code: the first three letters in capitals, a dash, and str(tickets).
6. Line 8print() with no values prints an empty line, separating the questions from the summary.
7. Line 9-10By default print() puts a single space between the values it is given.
8. Line 11The format code :.2f shows exactly two decimals, so 37.5 is printed as 37.50.
9. Line 12The booking code built on line 6 is printed: PRI-3.
10. Line 13sep=", " puts a comma and a space between the values, and end="!\n" adds an exclamation mark before the usual line break.

8Python Input/Output: common mistakes

boxes = input("How many boxes? ")
print("Items:", boxes * 2)

boxes = int(input("How many boxes? "))
print("Items:", boxes * 2)

price = int(input("Price: "))

price = float(input("Price: "))
print(price * 2)

total = 42.5
print("Total: " + total)

total = 42.5
print(f"Total: {total}")

9Python Input/Output: exercises

Write your answer, then press Check. The checks run in your browser.

Hello, Sam!

# read the name, then print the greeting

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

n = input("Number: ")
print(n * 3)
print(int(n) * 3)
print("A", "B", sep="-", end="!\n")
print(f"{int(n) / 3:.1f}")

Number: 4
444
12
A-B!
1.3

2 more exercises → 4 more examples

Further reading

• Python tutorial: an informal introduction
• Built-in types
• Lexical analysis (syntax rules)

10Next lesson

Related:
Python Exceptions: try, except, else and finallyPython File HandlingPython Calculator Project

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