Operators and Expressions

Introduction

Welcome to PyVerse! Today we'll learn how Python does math and makes decisions using operators and expressions. If you've ever solved 2 + 3 × 4 or asked "Is 10 bigger than 7?", you already know the idea. Let's turn those into code!

1) What is an expression?

An expression is a piece of code that Python can evaluate to a value.
It's made of values (like numbers or text), variables (like x or name), and operators (like +, -, and).
Example: 2 + 3 is an expression. So is name + "!" or (5 > 2).

2) Arithmetic operators (for numbers)

+ add
- subtract
* multiply
/ divide (always gives a decimal, even if it looks whole)
// floor division (whole number result)
% remainder (what's left after division)
** exponent (power)

Try these:

print(7 + 3)      # 10
print(7 - 3)      # 4
print(7 * 3)      # 21
print(7 / 3)      # 2.3333333333333335
print(7 // 3)     # 2
print(7 % 3)      # 1
print(2 ** 5)     # 32

3) Order of operations (who goes first?)

Parentheses go first: ( )
Then exponents: **
Then multiply and divide: * / // %
Then add and subtract: + -
Use parentheses to make your meaning clear.

print(2 + 3 * 4)     # 14 (multiply first)
print((2 + 3) * 4)   # 20 (parentheses first)

4) Variables and assignment

Use = to store a value in a variable.
You can update variables too.
Shortcuts: +=, -=, *=, /= update and reassign in one step.

x = 10
x = x + 5
print(x)   # 15

x += 5     # same as x = x + 5
print(x)   # 20

x *= 2
print(x)   # 40

5) Comparison operators (they give True or False)

== equal to
!= not equal to
> greater than
< less than
>= greater than or equal to
<= less than or equal to

print(5 == 5)   # True
print(5 != 3)   # True
print(7 > 10)   # False
print(8 <= 8)   # True

6) Logical operators (combine True/False)

and: both sides must be True
or: at least one side is True
not: flips True to False and vice versa

age = 14
is_teen = age >= 13 and age <= 19
print(is_teen)  # True

has_ticket = True
is_vip = False
can_enter = has_ticket or is_vip
print(can_enter)  # True

is_raining = False
print(not is_raining)  # True

7) Strings and operators

You can join strings with + (called concatenation).
You can repeat strings with *.

print("Hello" + " " + "World")  # Hello World
print("Ha" * 3)                 # HaHaHa

Be careful: you can't add a number to a string directly. Convert it first.

name = "Sam"
score = 15
print(name + " scored " + str(score) + " points!")  # Sam scored 15 points!

8) Mini exercise: Quick practice (5–7 minutes)

Calculations

Set width = 8 and height = 3. Make area using * and print it.
What is the remainder when 29 is divided by 5? Use % and print it.

Order matters

Print the results of 2 + 3 * 4 and (2 + 3) * 4.

Check conditions

Let temp = 24. Make a variable comfy that is True if temp is between 20 and 30 (inclusive). Print comfy.

Strings

Let name = "Ava" and stars = 4. Print "Ava earned 4 stars!" using + and str().

Sample answers (peek only after you try!)

width = 8
height = 3
area = width * height
print(area)              # 24

print(29 % 5)            # 4

print(2 + 3 * 4)         # 14
print((2 + 3) * 4)       # 20

temp = 24
comfy = (temp >= 20) and (temp <= 30)
print(comfy)             # True

name = "Ava"
stars = 4
print(name + " earned " + str(stars) + " stars!")

9) Summary

Expressions combine values, variables, and operators to make new values.
Arithmetic operators do math; comparison operators make True/False; logical operators combine True/False.
Use parentheses to control the order of operations.
Strings use + to join and * to repeat; convert types when needed with str() or int().

You're now ready to write smarter code that calculates and makes decisions!

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