# Class and Objects in Python Review

Perfect timing to review this before Django 👍  
Django is **very class-heavy**, so getting this clear will make everything feel easier.

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## What is a Class in Python?

A **class** is a blueprint (template) to create objects.

Think:

* **Class** → Design of a house 🏠
    
* **Object** → Actual house built from that design
    

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## What is an Object?

An **object** is an instance of a class.  
It holds **real data** and can use the class’s **methods**.

---

## Basic Example (Very Important)

```python
class Student:
    def __init__(self, name, roll):
        self.name = name
        self.roll = roll

    def info(self):
        print(self.name, self.roll)
```

### Creating Objects

```python
s1 = Student("Aarav", 1)
s2 = Student("Sita", 2)

s1.info()
s2.info()
```

### Output

```plaintext
Aarav 1
Sita 2
```

---

## Key Terms You MUST Know

### 1\. `__init__` (Constructor)

* Runs automatically when object is created
    
* Used to initialize data
    

```python
def __init__(self):
    pass
```

---

### 2\. `self`

* Refers to **current object**
    
* Without `self`, Django will break 😄
    

❌ Wrong:

```python
name = name
```

✅ Correct:

```python
self.name = name
```

---

## Class Variables vs Instance Variables

```python
class College:
    college_name = "ABC College"   # class variable

    def __init__(self, student):
        self.student = student     # instance variable
```

```python
c1 = College("Ram")
c2 = College("Shyam")

print(c1.college_name)
print(c2.college_name)
```

---

## Methods in Class

### Instance Method

```python
def show(self):
    print(self.name)
```

### Class Method

```python
@classmethod
def college(cls):
    print("ABC College")
```

### Static Method

```python
@staticmethod
def hello():
    print("Hello")
```

---

## Inheritance (VERY IMPORTANT FOR DJANGO)

```python
class User:
    def login(self):
        print("User logged in")

class Admin(User):
    def delete(self):
        print("Deleted")
```

```python
a = Admin()
a.login()
a.delete()
```

➡ Django uses inheritance everywhere (`models.Model`, `views.View`)

---

## Encapsulation (Basics)

```python
class Bank:
    def __init__(self, balance):
        self.__balance = balance  # private

    def get_balance(self):
        return self.__balance
```

---

## Why Classes Matter in Django (BIG PICTURE)

| Django Part | Class Usage |
| --- | --- |
| Models | `class Product(models.Model)` |
| Views | `class ProductView(View)` |
| Forms | `class ProductForm(forms.ModelForm)` |
| Admin | `class ProductAdmin(admin.ModelAdmin)` |

---

## Django-Style Preview Example

```python
class Product:
    def __init__(self, name, price):
        self.name = name
        self.price = price

    def discounted_price(self):
        return self.price - 10
```

➡ This is **exactly how Django Models think**, just with extra magic.

---

## Quick Practice Tasks (Before Django)

### Task 1

Create a class `Teacher` with:

* name
    
* subject
    
* method `details()`
    

---

### Task 2

Create a class `Car`:

* brand (class variable)
    
* model
    
* method `show()`
    

---

### Task 3 (Django mindset)

Create:

```python
class User:
    username
    email
    method: display()
```

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