Decisions and loops

if, elif, else, for and while.

Python uses indentation (four spaces) to group code. There are no braces.

age = 20
if age >= 18:
    print("adult")
elif age >= 13:
    print("teen")
else:
    print("child")

• Comparisons: == equal, != different, <, <=, >, >=.
• Combine with and, or, not.
• Check membership with in: "a" in "banana" is True.

Careful= assigns a value and == compares. Writing if x = 3: is an error.

for loops

for i in range(3):        # 0, 1, 2
    print(i)

for letter in "abc":
    print(letter)

while loops

count = 3
while count > 0:
    print(count)
    count -= 1

Use break to leave a loop early and continue to skip to the next round. Make sure a while loop eventually becomes false, or it runs forever (stop it with Ctrl+C).