Data Structure and Data Type

A data type tells Python:

“What kind of value is this?”

For example:

• 10 → integer
• "Hello" → string
• 3.14 → float

Python needs this so it knows:

• how to store the value
• what operations are allowed

Think of It Like This

If your program is a kitchen:

• Data = ingredients 🍅
• Data type = ingredient category
• (vegetable, fruit, liquid, spice)

🔢 Main Python Data Types

| Data Type | Description                     | Example        |
|-----------|---------------------------------|---------------|
| int       | Whole numbers                   | 10, -5, 200   |
| float     | Decimal numbers                 | 3.14, 2.5     |
| complex   | Complex numbers                 | 2+3j          |
| str       | Text                            | "Hello"       |
| bool      | True or False                   | True, False   |

1️⃣ Integer (int)

age = 25

Whole numbers:

• positive
• negative
• zero

2️⃣ Float (float)

price = 99.99

Numbers with decimal points.

3️⃣ String (str)

Text inside quotes:

name = "Danny"

You can use:

"Hello"
'Hello'

4️⃣ Boolean (bool)

Used for True / False:

is_logged_in = True

Very useful in:

• conditions
• comparisons
• login systems

5️⃣ Complex (complex)

Not common for beginners:

x = 2 + 3j

Used in scientific calculations.

What Are Data Structures?

A data structure is a way to:

store multiple values in one variable.

Instead of:

student1 = "John"
student2 = "Mary"
student3 = "David"

You can store them in one place.

Main Python Data Structures

| Data Structure | Description                         | Example                  |
|----------------|-------------------------------------|---------------------------|
| list           | Ordered, changeable collection      | [1, 2, 3]                 |
| tuple          | Ordered, unchangeable collection    | (1, 2, 3)                 |
| set            | Unordered, no duplicates            | {1, 2, 3}                 |
| dict           | Key-value pairs                     | {"name": "John"}          |

1. List ✅ (Most Common)

A list stores multiple items in order.

fruits = ["apple", "banana", "orange"]

Features:

✔ Ordered

✔ Changeable

✔ Allows duplicates

Accessing List Items

print(fruits[0])

Output:

apple

Changing List Items

fruits[1] = "grape"

2. Tuple

A tuple is like a list but:

❌ Cannot be changed after creation

numbers = (1, 2, 3)

Used when data should not change.

3. Set

A set:

• has no duplicates
• is unordered

unique_numbers = {1, 2, 3}

If you write:

{1, 1, 2, 2}

You get:

{1, 2}

4. Dictionary

Stores data in key → value format.

student = {
    "name": "Danny",
    "age": 25,
    "course": "Python"
}

Accessing Dictionary Data

print(student["name"])

Output:

Danny

Data Type vs Data Structure

| Feature        | Data Type                | Data Structure                     |
|---------------|---------------------------|------------------------------------|
| Meaning       | Type of a single value    | Stores multiple values             |
| Example       | int, float, string        | list, tuple, set, dictionary       |
| Usage         | Defines value behavior    | Organizes collections of data      |

Checking Data Types

Use:

type()

Example:

x = 10
print(type(x))

Output:

<class 'int'>

Type Conversion (Casting)

You can change data types:

age = "25"
age = int(age)

Type Casting Table

| Function | Converts To |
|----------|-------------|
| int()    | Integer     |
| float()  | Float       |
| str()    | String      |
| bool()   | Boolean     |

Real-Life Example

name = "Danny"        # string
age = 25              # int
height = 1.75         # float
is_student = True     # bool

courses = ["Python", "UI/UX"]   # list

student = {
    "name": name,
    "age": age
}

When to Use Each Data Structure

| Use Case                         | Best Choice |
|----------------------------------|------------|
| Store many items (changeable)    | List       |
| Store fixed data (unchangeable)  | Tuple      |
| Remove duplicates                | Set        |
| Store labeled data               | Dictionary |

Summary

✅ Data Types = single values

• int
• float
• string
• bool
• complex

✅ Data Structures = multiple values

• list
• tuple
• set
• dictionary

They help you:

• organize data
• write powerful programs
• build real applications