• Page Contents

__init__(self, ...) and __str__(self):

class Person:
    def __init__(self, name, age):
        self.name = name
        self.age = age

    def __str__(self):
        return f"{self.name}, {self.age} years old"

person = Person("Alice", 30)
print(person)  # Output: Alice, 30 years old

__del__(self):

class MyClass:
    def __del__(self):
        print("The object is being deleted.")

obj = MyClass()
del obj  # Output: The object is being deleted.

__add__(self, other):

class Point:
    def __init__(self, x, y):
        self.x = x
        self.y = y

    def __add__(self, other):
        return Point(self.x + other.x, self.y + other.y)

    def __str__(self):
        return f"({self.x}, {self.y})"

p1 = Point(1, 2)
p2 = Point(3, 4)
p3 = p1 + p2
print(p3)  # Output: (4, 6)

__getitem__(self, key):

class MyList:
    def __init__(self, data):
        self.data = data

    def __getitem__(self, index):
        return self.data[index]

my_list = MyList([1, 2, 3, 4, 5])
print(my_list[2])  # Output: 3

__setitem__(self, key, value) and __delitem__(self, key):

class MyList:
    def __init__(self, data):
        self.data = data

    def __setitem__(self, index, value):
        self.data[index] = value

    def __delitem__(self, index):
        del self.data[index]

    def __str__(self):
        return str(self.data)

my_list = MyList([1, 2, 3])
my_list[1] = 5
print(my_list)  # Output: [1, 5, 3]

del my_list[2]
print(my_list)  # Output: [1, 5]

__len__(self) and __contains__(self, item):

class CustomList:
    def __init__(self, data):
        self.data = data

    def __len__(self):
        return len(self.data)

    def __contains__(self, item):
        return item in self.data

custom_list = CustomList([1, 2, 3, 4, 5])
print(len(custom_list))  # Output: 5
print(3 in custom_list)  # Output: True
print(6 in custom_list)  # Output: False

__enter__(self) and __exit__(self, exc_type, exc_value, traceback):

class FileManager:
    def __init__(self, filename, mode):
        self.filename = filename
        self.mode = mode

    def __enter__(self):
        self.file = open(self.filename, self.mode)
        return self.file

    def __exit__(self, exc_type, exc_value, traceback):
        self.file.close()

with FileManager("example.txt", "w") as f:
    f.write("Hello, world!")

__bool__(self):

class NonEmptyList:
    def __init__(self, data):
        self.data = data

    def __bool__(self):
        return len(self.data) > 0

empty_list = NonEmptyList([])
non_empty_list = NonEmptyList([1, 2, 3])

if empty_list:
    print("Empty list is not empty.")
else:
    print("Empty list is empty.")

if non_empty_list:
    print("Non-empty list is not empty.")
else:
    print("Non-empty list is empty.")

__setattr__(self, name, value) and __getattr__(self, name):

class DynamicAttributes:
    def __init__(self):
        self._data = {}

    def __setattr__(self, name, value):
        self._data[name] = value

    def __getattr__(self, name):
        if name in self._data:
            return self._data[name]
        raise AttributeError(f"'DynamicAttributes' object has no attribute '{name}'")

obj = DynamicAttributes()
obj.attribute1 = 42
print(obj.attribute1)  # Output: 42
print(obj.attribute2)  # Raises AttributeError: 'DynamicAttributes' object has no attribute 'attribute2'