Python: Your First Program

The quickest way to start: open python.org/shell in your browser. To install it, download Python from python.org/downloads, then open the IDLE app that comes with it.

print("Hello, world!")

print() shows whatever you put inside the brackets. Text goes in quotes; numbers don't.

name = "Sam"
age = 29
print(f"Hi {name}, next year you'll be {age + 1}")

• = means “store this in”, not “equals”.
• An f-string (with an f before the quote) drops variables into text using { }.
• Common types: text (str), whole numbers (int), decimals (float), and True/False (bool).

answer = input("What's your name? ")   # waits for the user to type
print("Nice to meet you, " + answer)

temp = 31

if temp > 30:
    print("It's hot!")
elif temp > 15:
    print("Nice weather.")
else:
    print("Bring a coat.")

Indentation matters. Python uses the spaces at the start of a line to know what belongs inside the if. Use 4 spaces, and end the if line with a colon.

Comparisons: == equal, != not equal, >, <, >=, <=.

fruits = ["apple", "banana", "cherry"]
for fruit in fruits:
    print("I like", fruit)

for i in range(1, 4):
    print(i, "squared is", i * i)

range(1, 4) counts 1, 2, 3: it stops before the second number.