Dunder Methods
- Magic methods.
- Special methods in Python that are surrounded by double underscores.
-
are not meant to be invoked directly by the user but are internally invoked by the Python interpreter to perform specific actions.
E.g. when you wanna specify how two objects should be added together, you can define a
```py class Account: def __init__(self, balance: float): self.balance = balance class Credit: def __init__(self, amount: float): self.amount = amount def __add__(self, account: Account) -> float: return account.balance + self.amount my_account = Account(100) my_credit = Credit(20) print(my_credit + my_account) ```__add__method for your classes.
__init__
- The constructor method.
- Called when an object is instantiated.
- Used to initialize the object’s attributes.
- Will be used for things like performing any necessary setup or initialization tasks as well.
class Animal:
"""
Create an animal
Attributes:
name: The name of the animal.
species: The species of the animal.
"""
def __init__(self, name: str, species: str):
self.name = name
self.species = species
[!TIP]
In python we have in fact two method which will be called when an object is instantiated,
__new__and__init__.__new__is called first and it’s responsible for creating the object, while__init__is called second and it’s responsible for initializing the object.
__str__
- The string representation of an object.
- Used to provide a human-readable string representation of an object.
class BankAccount:
"""
Create a bank account
Attributes:
account_number: The account number.
balance: The balance of the account.
"""
def __init__(self, account_number: int, balance: float):
self.account_number = account_number
self.balance = balance
def __str__(self):
return f"Account Number: {self.account_number}, Balance: {self.balance}"
my_account = BankAccount(123456789, 1000.0)
print(my_account)