Classes: bank account

A class bundles related state and behavior into one object. __init__ sets up each instance, self refers to that instance, and methods are functions that act on it:

class Counter:
    def __init__(self, start=0):
        self.value = start      # per-instance state

    def bump(self):             # a method
        self.value += 1

c = Counter()
c.bump()
c.value      # 1

Your task

Write a BankAccount class that tracks a balance and remembers every transaction. It starts at a given balance and supports:

• deposit(amount) — add to the balance.
• withdraw(amount) — subtract, but only if there are enough funds; if not, leave the balance unchanged.
• history() — return the list of successful transaction amounts in order (deposits positive, withdrawals negative).

acc = BankAccount(100)
acc.deposit(50)        # balance 150
acc.withdraw(30)       # balance 120
acc.withdraw(1000)     # rejected — not enough funds
acc.balance            # 120
acc.history()          # [50, -30]

Hint: store self.balance in __init__ and keep a self.log list. In withdraw, guard with if amount <= self.balance: before applying it.