Question

# This program simulates a single transaction -
# either a deposit or a withdrawal - at a bank.
balance = 1000
type_of_transaction = input("Deposit or Withdrawl:")
amount=int(input("Enter Amount: $"))

if type_of_transaction == "Deposit":
balance=balance+amount

elif type_of_transaction == "Withdrawal":
balance=balance-amount
else:
print("Invalid Transaction.")

if balance<0:
print("You cannot have a negative balance!")

else:
print(f"Final balance: ${balance}")

Answer 1

Nice start — a few things to clean up:

Problems in the original
- Typo and case-sensitivity: your prompt says "Withdrawl" while you check for "Withdrawal", and you compare strings exactly so "deposit" or "withdraw" will be rejected.
- No validation for non-numeric or negative amounts (ValueError if user types letters).
- You allow a withdrawal that makes the balance negative and only then print a message — better to prevent the withdrawal if funds are insufficient.
- Using float for money can lead to rounding errors (optional improvement: use Decimal).

Here are two improved examples.

Simple, robust version (using float):
```
balance = 1000.0

t = input("Deposit or Withdrawal: ").strip().lower()
amount_str = input("Enter amount: $").strip()

try:
amount = float(amount_str)
if amount <= 0:
print("Amount must be greater than 0.")
else:
if t in ("deposit", "d"):
balance += amount
print(f"Final balance: ${balance:.2f}")
elif t in ("withdrawal", "withdraw", "w"):
if amount > balance:
print("Insufficient funds. Transaction cancelled.")
else:
balance -= amount
print(f"Final balance: ${balance:.2f}")
else:
print("Invalid transaction type.")
except ValueError:
print("Invalid amount entered.")
```

More accurate money handling (use Decimal):
```
from decimal import Decimal, InvalidOperation, getcontext
getcontext().prec = 10

balance = Decimal("1000.00")

t = input("Deposit or Withdrawal: ").strip().lower()
amount_str = input("Enter amount: $").strip()

try:
amount = Decimal(amount_str)
if amount <= 0:
print("Amount must be greater than 0.")
else:
if t in ("deposit", "d"):
balance += amount
print(f"Final balance: ${balance:.2f}")
elif t in ("withdrawal", "withdraw", "w"):
if amount > balance:
print("Insufficient funds. Transaction cancelled.")
else:
balance -= amount
print(f"Final balance: ${balance:.2f}")
else:
print("Invalid transaction type.")
except InvalidOperation:
print("Invalid amount entered.")
```

If you want, I can:
- Add a loop to allow multiple transactions,
- Persist the balance between runs (file or database),
- Show a transaction history,
- Or adapt this into a small CLI menu. Which would you like?