Python ATM登录验证逻辑异常：账户不存在时提示功能失效问题排查

Let's break down why your code fails when an invalid account number is entered, and fix it step by step.

The Root Cause #

Your line correct_pin= valid_pins[valid_accounts.index(account)] runs before you check if the account exists in valid_accounts. If the account isn't in the list, valid_accounts.index(account) throws a ValueError (since it can't find the account to get its index), and your code crashes before reaching the invalid login check.

Quick Fix (Keep Existing List Structure) #

We need to rearrange the logic to first verify the account exists, then fetch the corresponding PIN only if it does:

account_name = ['Adetunji Michael', 'Dina Asher-Smith', 'Niyola Davidson', 'John Paul']
valid_accounts= [3455590445, 2871290429, 3599076267, 1234567890]
valid_pins = [34777, 45786, 24055, 12345]
account_balance= [112000, 45700, 2300, 30000]

# Interface setup
print(" *************************")
print(" ABC BANK OF NIGERIA.\n MARVELLING YOU SINCE 2003\n WELCOME TO THE ATM MACHINE.")
print(" *************************")

trials=3
while trials!=0:
    account= int(input(" PLEASE INPUT YOUR ACCOUNT NUMBER: "))
    pin = int(input(" PLEASE INPUT YOUR 5 DIGIT PIN: "))
    
    # First check if account exists
    if account not in valid_accounts:
        print(" INVALID LOGIN DETAILS. ")
        trials -=1
        print(" YOU HAVE ", trials, " TRIALS LEFT")
    else:
        # Now safely get the matching PIN since account is valid
        account_index = valid_accounts.index(account)
        correct_pin = valid_pins[account_index]
        if pin != correct_pin:
            print(" INVALID LOGIN DETAILS. ")
            trials -=1
            print(" YOU HAVE ", trials, " TRIALS LEFT")
        else:
            print(f"Welcome {account_name[account_index]}!")
            # Add your post-login logic here (balance check, withdrawal, etc.)
            break  # Exit loop after successful login

Better Approach: Use Dictionaries for Data Association #

Storing related data (account, PIN, name, balance) in separate lists is error-prone (easy to mix up indices). A cleaner way is to use a dictionary where each account number maps to its details:

# Organize data into a single dictionary for clarity and safety
customer_data = {
    3455590445: {"name": "Adetunji Michael", "pin": 34777, "balance": 112000},
    2871290429: {"name": "Dina Asher-Smith", "pin": 45786, "balance": 45700},
    3599076267: {"name": "Niyola Davidson", "pin": 24055, "balance": 2300},
    1234567890: {"name": "John Paul", "pin": 12345, "balance": 30000}
}

# Interface setup
print(" *************************")
print(" ABC BANK OF NIGERIA.\n MARVELLING YOU SINCE 2003\n WELCOME TO THE ATM MACHINE.")
print(" *************************")

trials=3
while trials!=0:
    account= int(input(" PLEASE INPUT YOUR ACCOUNT NUMBER: "))
    pin = int(input(" PLEASE INPUT YOUR 5 DIGIT PIN: "))
    
    # Check if account exists in our data
    if account not in customer_data:
        print(" INVALID LOGIN DETAILS. ")
        trials -=1
        print(" YOU HAVE ", trials, " TRIALS LEFT")
    else:
        # Verify PIN against the stored value
        if pin != customer_data[account]["pin"]:
            print(" INVALID LOGIN DETAILS. ")
            trials -=1
            print(" YOU HAVE ", trials, " TRIALS LEFT")
        else:
            print(f"Welcome {customer_data[account]['name']}!")
            # Access balance or other data easily: customer_data[account]['balance']
            break

This approach eliminates index-related bugs entirely and makes your code much easier to maintain when adding/removing customers.

内容的提问来源于stack exchange，提问作者user16342430