Operations

Python · Unit 1: First steps

+, -, * and / work like on a calculator.

Watch out: / always gives a decimal (float), even when the division is exact.

print(3 * 4)
print(8 / 2)

Prints

12
4.0

// divides and keeps the whole part.

% gives what's left over from the division, and ** raises to a power.

print(7 // 2)
print(7 % 2)
print(2 ** 3)

Prints

3
1
8

Python follows the same order as at school: first **, then *, /, // and %, and + and - at the end.

Whatever goes inside parentheses is worked out before anything else.

print(10 - 2 * 3)
print((10 - 2) * 3)

Prints

4
24

Exercises in this lesson

You do them in the app, which checks them on the spot and explains why.

1. Predict the output
What does this code print?
```
pizza = 8
people = 4
print(pizza / people)
```
2. Put the lines in order
Order the lines to work out a bill with a 20 % tip.
3. Find the bug
This program should print how many minutes there are in 3 hours. Which line has the error?
```
hours = 3
minutes = hours * 6
print(minutes)
```
4. Predict the output
What does this code print?
```
print(10 % 3)
```
5. Multiple choice
What is 9 // 2 worth?
6. Complete the code
Fill in so it prints 8 and then 1.
```
print(17 ___ 2)
print(17 ___ 2)
```
7. Complete the code
A number is even if dividing it by 2 leaves 0. Fill in to see what's left over.
```
number = 14
print(number ___ 2)
```
8. Predict the output
Python multiplies before it adds. What does it print?
```
print(2 + 3 * 4)
```
9. Find the bug
This program should print the average of 4 and 6. Which line has the error?
```
a = 4
b = 6
average = a + b / 2
print(average)
```
10. Put the lines in order
Order the lines to work out the area of a square with side 5 (side times side).

11. Predict the output

How many hours and minutes are 135 minutes?

minutes = 135
hours = minutes // 60
rest = minutes % 60
print(hours, "h", rest, "min")

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