readme.md

Lesson 2: Variables and Data Types

Back to the main roadmap | Previous lesson: Basic Syntax | Next lesson: Conditionals

What is a Variable?

Think of a variable as a labeled box.

You can store something inside the box and give it a name so you can use it later.

Example

age = 10

Here:

• age is the name of the box.
• 10 is the value stored inside the box.

You can access the value anytime.

age = 10
print(age)

Output

10

---

Variables Can Change

The value stored in a variable can be changed at any time.

Example

age = 10
age = 11

print(age)

Output

11

The old value (10) is replaced by the new value (11).

---

Data Types

Different kinds of values are stored using different data types.

Data Type	Description	Example
int	Whole numbers	age = 10
float	Numbers with decimal points	height = 4.5
str	Text (String)	name = "Alex"
bool	Only True or False	is_student = True

---

Integer (int)

Stores whole numbers.

Example

age = 10
print(age)

Output

10

---

Float (float)

Stores decimal numbers.

Example

height = 4.5
print(height)

Output

4.5

---

String (str)

Stores text.

Strings are written inside single quotes (' ') or double quotes (" ").

Example

name = "Alex"
print(name)

Output

Alex

---

Boolean (bool)

A Boolean can have only one of two values:

• True
• False

Example

is_student = True
print(is_student)

Output

True

---

Python Automatically Detects the Data Type

Python is smart enough to determine the data type based on the value you assign.

You don't need to specify the type yourself.

Example

age = 10
height = 5.8
name = "Alex"
is_student = True

Python automatically understands:

• 10 → int
• 5.8 → float
• "Alex" → str
• True → bool

---

Checking the Data Type

Use the type() function to find the data type of a variable.

Example

age = 10

print(type(age))

Output

<class 'int'>

Another example:

name = "Alex"

print(type(name))

Back to the main roadmap | Previous lesson: Basic Syntax | Next lesson: Conditionals

Output

<class 'str'>

---

Variable Naming Rules

Follow these rules when naming variables.

✅ Rule 1: No Spaces

# Correct
my_age = 20

# Incorrect
my age = 20

---

✅ Rule 2: Cannot Start with a Number

# Correct
age1 = 20

# Incorrect
1age = 20

---

✅ Rule 3: Variable Names are Case-Sensitive

age = 20
Age = 30

print(age)
print(Age)

Output

20
30

age and Age are considered two different variables.

---

Key Takeaways

• A variable is a named container used to store data.

• Variables can be updated by assigning a new value.

• Python has four common data types:

  • int
  • float
  • str
  • bool

• Use type() to check the data type of a variable.

• Variable names cannot contain spaces or start with numbers.

• Python is case-sensitive (age and Age are different).

---

Next Lesson: Conditionals