Merge pull request #1111 from Santhosh-Siddhardha/main

Added Content on Magic Methods under Advanced Python Module
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Ashita Prasad 2024-06-18 06:49:22 +05:30 zatwierdzone przez GitHub
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- [Reduce](reduce-function.md)
- [List Comprehension](list-comprehension.md)
- [Eval Function](eval_function.md)
- [Magic Methods](magic-methods.md)

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# Magic Methods
Magic methods, also known as dunder (double underscore) methods, are special methods in Python that start and end with double underscores (`__`).
These methods allow you to define the behavior of objects for built-in operations and functions, enabling you to customize how your objects interact with the
language's syntax and built-in features. Magic methods make your custom classes integrate seamlessly with Pythons built-in data types and operations.
**Commonly Used Magic Methods**
1. **Initialization and Representation**
- `__init__(self, ...)`: Called when an instance of the class is created. Used for initializing the object's attributes.
- `__repr__(self)`: Returns a string representation of the object, useful for debugging and logging.
- `__str__(self)`: Returns a human-readable string representation of the object.
**Example** :
```python
class Person:
def __init__(self, name, age):
self.name = name
self.age = age
def __repr__(self):
return f"Person({self.name}, {self.age})"
def __str__(self):
return f"{self.name}, {self.age} years old"
p = Person("Alice", 30)
print(repr(p))
print(str(p))
```
**Output** :
```python
Person("Alice",30)
Alice, 30 years old
```
2. **Arithmetic Operations**
- `__add__(self, other)`: Defines behavior for the `+` operator.
- `__sub__(self, other)`: Defines behavior for the `-` operator.
- `__mul__(self, other)`: Defines behavior for the `*` operator.
- `__truediv__(self, other)`: Defines behavior for the `/` operator.
**Example** :
```python
class Vector:
def __init__(self, x, y):
self.x = x
self.y = y
def __add__(self, other):
return Vector(self.x + other.x, self.y + other.y)
def __repr__(self):
return f"Vector({self.x}, {self.y})"
v1 = Vector(2, 3)
v2 = Vector(1, 1)
v3 = v1 + v2
print(v3)
```
**Output** :
```python
Vector(3, 4)
```
3. **Comparison Operations**
- `__eq__(self, other)`: Defines behavior for the `==` operator.
- `__lt__(self, other)`: Defines behavior for the `<` operator.
- `__le__(self, other)`: Defines behavior for the `<=` operator.
**Example** :
```python
class Person:
def __init__(self, name, age):
self.name = name
self.age = age
def __eq__(self, other):
return self.age == other.age
def __lt__(self, other):
return self.age < other.age
p1 = Person("Alice", 30)
p2 = Person("Bob", 25)
print(p1 == p2)
print(p1 < p2)
```
**Output** :
```python
False
False
```
5. **Container and Sequence Methods**
- `__len__(self)`: Defines behavior for the `len()` function.
- `__getitem__(self, key)`: Defines behavior for indexing (`self[key]`).
- `__setitem__(self, key, value)`: Defines behavior for item assignment (`self[key] = value`).
- `__delitem__(self, key)`: Defines behavior for item deletion (`del self[key]`).
**Example** :
```python
class CustomList:
def __init__(self, *args):
self.items = list(args)
def __len__(self):
return len(self.items)
def __getitem__(self, index):
return self.items[index]
def __setitem__(self, index, value):
self.items[index] = value
def __delitem__(self, index):
del self.items[index]
def __repr__(self):
return f"CustomList({self.items})"
cl = CustomList(1, 2, 3)
print(len(cl))
print(cl[1])
cl[1] = 5
print(cl)
del cl[1]
print(cl)
```
**Output** :
```python
3
2
CustomList([1, 5, 3])
CustomList([1, 3])
```
Magic methods provide powerful ways to customize the behavior of your objects and make them work seamlessly with Python's syntax and built-in functions.
Use them judiciously to enhance the functionality and readability of your classes.