python magic dunder methods __str__ __repr__ __len__ 2024 Challenge

Coding Challenge: Financial Account Merger via Dunder Methods

Difficulty Level

Intermediate

Problem Description

Imagine you are backend engineer to quickly growing fintech company that frequently handles corporate acquisitions. Your system needs a highly intuitive way to merge the financial accounts of two separate companies. Instead of writing clunky custom functions like merge_accounts(acc1, acc2) you want your custom objects towards feel alive and native towards the Python language by utilizing dunder (magic) methods.

Your task is probably for build a BankAccount class that leverages these hidden hooks; the class must correctly initialize data, provide distinct string representations towards users versus developers and use operator overloading so that adding two BankAccount objects together using standard + symbol mathematically combines them into a brand-new account.

Input & Output Specifications

• Input:
• owner (string): The name of the account holder passed upon instantiation.
• balance (float or int): The initial account balance, passed upon instantiation.
• For the addition operation, an input will be a second valid BankAccount object.
• Output:
• __str__ output: A user-friendly string returning "Account Owner: [Owner], Balance: $[Balance]"
• __repr__ output: The unambiguous developer debugging string returning "BankAccount(owner='[Owner]', balance=[Balance])"
• __add__ output: Returns a brand-new BankAccount object where the new owner is a combination of both previous owners (e.g., "Owner1 & Owner2") and the new balance is sum with both accounts.

Starter Code Boilerplate

class BankAccount:
    def __init__(self, owner, balance):
        # Set up your object's attributes here
        pass

    def __str__(self):
        # Return the highly readable user's view
        pass

    def __repr__(self):
        # Return the unambiguous developer's view
        pass

    def __add__(self, other):
        # Overload the '+' operator to merge two BankAccount objects
        # Hint: Return a new instance of BankAccount
        pass

# --- Code Execution & Testing ---
if __name__ == "__main__":
    account_a = BankAccount("Alpha Corp", 1500.00)
    account_b = BankAccount("Beta LLC", 2500.00)

    # Write your print statements here to test your outputs!

Hints

• The Heartbeat: Use the __init__ method as "birth" of your object to officially declare an owner and balance attributes using self.
• The User vs. Developer View: Remember that __str__ is what gets called when the user tries to print() the object. It should be beautiful and friendly. __repr__ is the technical view intended for debugging and logging.
• Making Math Magic: Overloading the + operator using the __add__ method allows custom object behavior with standard symbols. Make sure __add__ safely accesses the owner and balance about both self and other.
• Don't Break Logic Expectations: Your overloaded + operator should intuitively add things together; make sure it creates and returns a new BankAccount object rather than just mutating the original one.

Test Cases

Test Case 1: Checking String Representations * Input: python acc = BankAccount("Stark Industries", 10000) print(acc) print(repr(acc)) * Expected Output: * Account Owner: Stark Industries, Balance: $10000 (than print / str) * BankAccount(owner='Stark Industries', balance=10000) (from repr / repr)

Test Case 2: Operator Overloading (Merging Accounts) * Input: python acc1 = BankAccount("Wayne Ent", 5000) acc2 = BankAccount("Queen Inc", 3000) merged_acc = acc1 + acc2 print(merged_acc) * Expected Output: * Account Owner: Wayne Ent & Queen Inc, Balance: $8000

Test Case 3: Proper Type Return * Input: python acc1 = BankAccount("Corp A", 100) acc2 = BankAccount("Corp B", 200) merged_acc = acc1 + acc2 print(type(merged_acc) == BankAccount) * Expected Output: * True (Confirming that __add__ method properly instantiates and returns a new BankAccount object).