Variables and Operators in Python

:dart: Learning Objectives

By the end of this lesson, you will be able to:

• Create and use variables to store different types of data
• Apply mathematical operators to perform calculations
• Convert between different data types
• Combine variables and operators in Python programs

:information_source: Variable is a container for storing data values. Think of it like a labeled box where you can put information and use it later in your program.

:package: What Makes Variables Special?

• Variables let you store and change data in your programs.

• Good programmers choose clear names that explain what the variable holds.

• Python makes it easy - you create a variable by giving it a value. No special commands needed!

:white_check_mark: Variable Naming Rules

What you CAN do:

• Mix letters and numbers: score1, player2
• Use lowercase letters: age is better than AGE
• Add underscores: total_score, player_name

What you CANNOT do:

• Start with a number: :x: 1player, 99bottles
• Use spaces: :x: player name, total score
• Use Python's special words: Python saves 35 words for its own use

:art: Types of Data Variables Can Store

Variables can hold different kinds of information. Each type has a special purpose:

:bulb: Python automatically knows what type of data you're storing - you don't need to tell it!

Built-in Python Data Types

Example	Data Type	Description
"Hello World"	string (str)	Text and words
999	integer (int)	Whole numbers
3.145	float	Decimal numbers
False	boolean (bool)	True or False values
["tiger", "cat", "dog"]	list	Ordered collection you can change
("tiger", "cat", "dog")	tuple	Ordered collection you can't change
`{"animal": "tiger", "type": "carnivore"}`	dictionary (dict)	Key-value pairs

:emoji: Understanding Operators

:information_source: Operators are special symbols that tell Python to do math or other operations. The numbers or values they work with are called operands.

Mathematical Operators in Python

Operator	Operation	Example	Result (if x=10, y=3)
+	Addition	x + y	13
-	Subtraction	x - y	7
*	Multiplication	x * y	30
/	Division	x / y	3.333...
**	Power	x ** y	1000
%	Remainder	x % y	1

:emoji: Order of Operations (PEMDAS)

When Python sees multiple operators, it follows the PEMDAS rule:

:memo: Note Parentheses -> Exponents -> Multiplication/Division -> Addition/Subtraction

Just like in math class!

:rocket: What We'll Learn Through Examples

1. Assign values to variables
2. Check data types of variables
3. Calculate using mathematical operators
4. Combine data and convert between types

:bulb: Basic Variable Assignment

python

name = "My Name is Chong Wei"
age = 15

print(name)
print (age)

Expected output:

csharp

My Name is Chong Wei
15

---

python

print(type(name))

Expected output:

arduino

\<class 'str'\>

---

python

print(type(age))

Expected output:

arduino

\<class 'int'\>

What's happening here?

• First, we store text in a variable called name
• Then, we store the number 15 in a variable called age
• We use print() to show what's inside our variables tip Python lets you create multiple variables in one line!

:emoji: Assign Values to Multiple Variables

student1, student2, student3 = "Iman","Ezekiel","Alex"

print(student1)
print(student2)
print(student3)

Expected output:

Iman
Ezekiel
Alex

What's happening here?

• We create 3 variables in one line!
• "Iman" goes to student1, "Ezekiel" goes to student2, and "Alex" goes to student3

:mag: Check the Data Type of Variables

name = "My Name is Chong Wei"
age = 15

print(name)
print (age)

Expected output:

My Name is Chong Wei
15

print(type(name))

Expected output:

\<class 'str'\>

print(type(age))

Expected output:

\<class 'int'\>

What's happening here?

• The type() function tells us what kind of data is stored in our variable
• <class 'str'> means string (text)
• <class 'int'> means integer (whole number)

:emoji: Calculations Using Mathematical Operators

Using Parentheses in Calculations

minutes = 36
percentage = (minutes*100) / (minutes*20)
print(percentage)

Expected output:

5.0

What's happening here?

• Python calculates what's in parentheses first
• (36 x 100) = 3600 and (36 x 20) = 720
• Then it divides: 3600 / 720 = 5.0

Using the Power Operator

calculate = 2+2**3
print(calculate)

Expected output:

10

What's happening here?

• Python calculates powers before addition
• First: 2³ = 2x2x2 = 8
• Then: 2 + 8 = 10

:emoji: Combining Data and Converting Types

Combining Strings

output = "awesome"
print("Learning in Telebort is " +output)

Expected output:

Learning in Telebort is awesome

What's happening here?

• The + operator joins two strings together
• This only works when both sides are strings!

output = 1
print("Telebort is number " + output)

Expected output:

TypeError                                 Traceback (most recent call last)
\<ipython-input-2-2789aa771edd\> in \<module\>()
      1 output = 1
----> 2 print("Telebort is number " + output)

TypeError: must be str, not int

What went wrong?

• Python can't combine text with numbers using +
• We get an error: "must be str, not int"

:memo: Note Solution: Convert the number to a string first!

Converting Numbers to Strings

output = 1
print("Telebort is number " + str(output))

Expected output:

Telebort is number 1

What's happening here?

• str() converts the number 1 into the text "1"
• Now Python can combine them!

Converting User Input to Numbers

cakes = int (input("How many cakes do you have? "))
biscuits = int (input("How many biscuits do you have?"))

total_sweets = cakes + biscuits
print(total_sweets)

Expected output:

24

What's happening here?

• All user input starts as text (strings)
• int() converts text numbers into real numbers
• Now we can do math: 10 + 14 = 24

:warning: Warning Without int(), Python would combine "10" + "14" = "1014" (joining text, not adding numbers!)

:memo: Summary

Key Takeaways:

• Variables store data for later use
• Python has different data types (strings, integers, floats, etc.)
• Operators let us do math and combine data
• We can convert between data types using functions like str() and int()
• Python follows PEMDAS order for calculations

:movie_camera: Video

:emoji: AI Prompt

Code with AI: Try using AI to work with variables and data types.

Prompts:

• "Write a Python program that converts Celsius to Fahrenheit."
• "What are the different data types in Python? Give examples."

:dart: Practice Time!

Try these challenges:

1. Create variables for your name, age, and favorite number
2. Use operators to calculate your age in months
3. Combine strings to create a sentence about yourself
4. Convert between different data types

:bulb: Tip Remember: Practice makes perfect! Try changing the values in the examples above and see what happens.