E Wallet — Code

def deposit(self, amount): if amount <= 0: return "Amount must be positive" self.balance += amount self._log_transaction("DEPOSIT", amount) return f"Deposited $amount. New balance: $self.balance"

print(f"Alice balance: $alice.balance") print(f"Bob balance: $bob.balance")

def pay(self, amount, recipient_wallet): if amount <= 0: return "Amount must be positive" if self.balance < amount: return "Insufficient balance" e wallet code

This works for a script, but real e-wallet code is much more complex. 1. Concurrency & Race Conditions Imagine two API calls trying to deduct from the same balance at the same time. Without proper locking or database transactions, users could overspend.

We all use e-wallets daily. Tap your phone, scan a QR code, or send money to a friend—it feels like magic. But as a developer, I know there’s a lot more happening under the hood. def deposit(self, amount): if amount <= 0: return

def _log_transaction(self, txn_type, amount, counterparty=None): txn = "id": str(uuid.uuid4()), "type": txn_type, "amount": amount, "timestamp": datetime.utcnow().isoformat(), "counterparty": counterparty, "balance_after": self.balance self.transactions.append(txn) alice = SimpleWallet("alice_123") bob = SimpleWallet("bob_456")

Want to go deeper? Try building a simple wallet with and add a mock payment gateway. You’ll learn more than any tutorial can teach. Have you built a payment or wallet system before? What was your biggest technical challenge? Let me know in the comments. Concurrency & Race Conditions Imagine two API calls

self._log_transaction("SEND", amount, recipient_wallet.user_id) recipient_wallet._log_transaction("RECEIVE", amount, self.user_id)