Operators and Control Flow

>Operators and Control Flow — cheat sheet

Use expressions, decisions, and loops to make your program calculate and choose what happens next.

Arithmetic and assignment

total = 17
people = 4
print(total // people)

// keeps the whole-number result of division.

print(17 % 4)

% gives the remainder after division.

print(2 ** 5)

** raises a number to a power.

score = 8
score += 4

Update a value by adding and assigning.

print(5 >= 5)

Comparisons produce True or False.

print(age >= 18 and has_ticket)

and needs both conditions to be true.

print("py" in "python")

in checks whether a value appears in a collection.

value = None
print(value is None)

Use is to check whether a value is None.

name = "Mina"
points = 42
print(f"{name} has {points} points.")

An f-string places values or expressions inside text.

price = 3.5
print(f"${price:.2f}")

:.2f shows a number with two decimal places.

entered_age = "12"
age = int(entered_age)

input returns text, so convert numeric input before calculating.

match "start":
    case "start":
        print("Starting")
    case _:
        print("Unknown")

match-case chooses code for fixed values; _ is the fallback.

if score >= 90:
    print("A")

Run an indented block only when its condition is true.

if age < 18:
    print("Junior")
else:
    print("Adult")

else is the fallback when if is false.

if score >= 80:
    grade = "B"
elif score >= 70:
    grade = "C"

elif checks another condition after if.

label = "has text" if "go" else "empty"

A conditional expression makes a short two-way choice.

for letter in "cat":
    print(letter)

Visit each character or item in order.

for number in range(2, 8, 2):
    print(number)

range starts, stops before, and steps through numbers.

for index, item in enumerate(["pear", "plum"], start=1):
    print(index, item)

enumerate supplies both a position and an item.

for name, score in zip(["Ana", "Bo"], [9, 7]):
    print(name, score)

zip pairs values from two collections.

count = 1
while count <= 3:
    count += 1

A while loop repeats while its condition stays true.

for number in range(5):
    if number == 3:
        break

break exits the nearest loop early.

for number in range(5):
    if number == 3:
        continue
    print(number)

continue skips the rest of one loop repeat.

if True:
    pass

pass is a placeholder that does nothing.