OOP

class BankAccount:
    bank_name = "State Bank"  # class variable (shared)

    def __init__(self, holder: str, balance: float = 0):
        self.holder = holder       # instance variable
        self.__balance = balance   # private (name mangling)

    def deposit(self, amount: float) -> None:
        if amount <= 0: raise ValueError("Amount must be positive")
        self.__balance += amount

    def withdraw(self, amount: float) -> bool:
        if amount > self.__balance: return False
        self.__balance -= amount
        return True

    @property
    def balance(self) -> float:  # getter
        return self.__balance

    def __str__(self):  # string representation
        return f"Account({self.holder}: ₹{self.__balance:,})"

    @classmethod
    def create_savings(cls, holder: str):
        return cls(holder, balance=1000)  # factory method

from abc import ABC, abstractmethod

class Vehicle(ABC):
    def __init__(self, id: str, capacity: int):
        self.id = id
        self.capacity = capacity
        self._is_available = True

    @abstractmethod
    def fare_per_km(self) -> float:
        pass

    def estimate_fare(self, distance_km: float) -> float:
        return round(distance_km * self.fare_per_km(), 2)

    @property
    def is_available(self): return self._is_available

class Auto(Vehicle):
    def fare_per_km(self): return 12.0

class Cab(Vehicle):
    def __init__(self, id, capacity, is_premium=False):
        super().__init__(id, capacity)
        self.is_premium = is_premium

    def fare_per_km(self): return 18.0 if not self.is_premium else 28.0

auto = Auto("AUTO-042", capacity=3)
cab  = Cab("CAB-117", capacity=4, is_premium=True)

print(auto.estimate_fare(5))   # ₹60.0
print(cab.estimate_fare(5))    # ₹140.0