Statement
Solution
Python Exercise 8.2: Bank Account System
Classes are perfect for modelling real-world systems. Build a BankAccount class that manages deposits, withdrawals, and balance checks with proper validation.
Your class should:
- Define a class called
BankAccount. - Include an
__init__method that accepts anownername and an optionalbalance(default0). - Include a
deposit(amount)method that adds the amount to the balance. Print a confirmation message. Reject deposits of 0 or less. - Include a
withdraw(amount)method that deducts the amount. Reject withdrawals that exceed the current balance or are 0 or less, printing an appropriate message each time. - Include a
get_balance()method that prints the current balance. - Demonstrate the class with a series of transactions as shown below.
Sample Interaction:
Input
Output
(None)
Deposited $500. New balance: $500
Deposited $200. New balance: $700
Withdrew $150. New balance: $550
Error: Insufficient funds.
Balance for Alice: $550
Solution
Each method validates its input before modifying the balance, keeping the object in a consistent state at all times.
class BankAccount:
def __init__(self, owner, balance=0):
self.owner = owner
self.balance = balance
def deposit(self, amount):
if amount <= 0:
print("Error: Deposit amount must be positive.")
return
self.balance += amount
print(f"Deposited ${amount}. New balance: ${self.balance}")
def withdraw(self, amount):
if amount <= 0:
print("Error: Withdrawal amount must be positive.")
return
if amount > self.balance:
print("Error: Insufficient funds.")
return
self.balance -= amount
print(f"Withdrew ${amount}. New balance: ${self.balance}")
def get_balance(self):
print(f"Balance for {self.owner}: ${self.balance}")
# Demo
account = BankAccount("Alice")
account.deposit(500)
account.deposit(200)
account.withdraw(150)
account.withdraw(1000)
account.get_balance()
Key Concepts:
- Default parameter values (e.g.
balance=0) make arguments optional. - Guard clauses with
returnexit a method early when validation fails. - Instance attributes (
self.balance) persist across all method calls on the same object. - Methods can both modify state and communicate results via
print().
Test Console
Run code to see output...
