Input, Output & Operators

Talk to the user, do maths, and combine text neatly with f-strings.

print() — sending output

You've already met print. It accepts multiple things separated by commas:

print("Score:", 42)
print("x", "y", "z", sep="-")
print("loading", end="...")
print("done")

input() — asking the user a question

input() shows a prompt, waits for the user to type something and press Enter, and returns whatever they typed as a string:

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

If you want a number, convert it:

age_text = input("How old are you? ")
age = int(age_text)
print("Next year you'll be", age + 1)

Maths operators

print(2 + 3)    # 5  — add
print(10 - 4)   # 6  — subtract
print(6 * 7)    # 42 — multiply
print(9 / 2)    # 4.5 — divide (always returns a float)
print(9 // 2)   # 4   — integer divide (drops the remainder)
print(9 % 2)    # 1   — remainder (modulo)
print(2 ** 10)  # 1024 — power (2 to the 10th)

Comparison operators

These return a boolean (True or False):

print(3 == 3)   # True   — equal to
print(3 != 4)   # True   — not equal
print(5 > 2)    # True
print(5 <= 5)   # True

String operators

You can stick strings together with + and repeat them with *:

print("Py" + "thon")   # Python
print("ha" * 3)         # hahaha

f-strings — the nicest way to combine text and values

Put an f before the opening quote, then put any expression inside { }:

name = "Pat"
score = 87

print(f"{name} scored {score}/100")
print(f"That's {score / 100:.0%}")

The bit after the : is an optional format spec — useful examples:

• {value:.2f} — show 2 decimal places (3.14)
• {value:.0%} — show as a percent with no decimals (87%)
• {value:,} — thousands separators (1,000,000)

A tiny program tying it together

name = input("Your name: ")
price = float(input("Item price: "))
qty = int(input("Quantity: "))

total = price * qty
print(f"Thanks {name} — your total is £{total:.2f}")