如何为Python简易ATM程序添加5000元最低账户余额限制？

一、新增取款后最低余额5000限制 #

方式1：直接用if-else语句修改取款逻辑 #

在原代码的取款分支（opt == 2）中，增加对取款后余额的判断，确保余额不低于5000，同时优化输入校验避免程序报错：

import time
print("Welcome to OtnisBank")
print("Please insert your card...")
time.sleep(5)
pwd = 1234
pin = int(input("Please enter your security pin: "))
bal = 737000
transaction_Num = 20221000114
while True:

    if pin == pwd:
        print("""
        ********************************************         
                    1) Balance
                    2) Withdraw
                    3) Deposit
                    4) Cancel Transaction       
        ********************************************        
             
            """)
        try:
            opt = int(input("Please choose your transaction "))
        except ValueError:
            print("Invalid input, input must be an integer.")
            continue

        if opt == 1:
            print(f"Your current balance is ₱{bal}.00")

        if opt == 2:
            print("Maximum of 100k per transaction | Minimum balance after withdrawal: ₱5000.00")
            try:
                withdraw = int(input("Please enter amount: "))
            except ValueError:
                print("Invalid input, amount must be an integer.")
                continue
            
            # 检查单笔取款上限
            if withdraw > 100000:
                print("Invalid amount, maximum of 100k per transaction.")
            # 检查取款后余额是否达标
            elif bal - withdraw < 5000:
                max_withdraw = bal - 5000
                print(f"Invalid amount, balance must remain at least ₱5000.00. You can withdraw up to ₱{max_withdraw}.00")
            else:
                bal = bal - withdraw
                print(f"₱{withdraw}.00 is withdrawn from your account...")
                print(f"Your updated balance is ₱{bal}.00")

        if opt == 3:
            try:
                deposit = int(input("How much money would you like to deposit?: "))
            except ValueError:
                print("Invalid input, amount must be an integer.")
                continue
            bal = bal + deposit
            print(f"₱{deposit}.00 is deposited unto your account...")
            print(f"Your updated balance is ₱{bal}.00")

        if opt == 4:
            print("Transaction success...")
            print(f"Transaction number: {transaction_Num + 1}")
            print(
                "Thank you for choosing our bank. Invest in the red, it's in your best interest.")
            break
    else:
        print("Please enter a valid pin and try again.")
        break

方式2：封装为可复用函数 #

把取款校验逻辑封装成独立函数，便于后续维护和规则修改：

import time

def can_withdraw(balance, amount, max_single=100000, min_balance=5000):
    """校验取款是否合法，返回(是否允许, 提示信息)"""
    if amount <= 0:
        return False, "Amount must be a positive integer."
    if amount > max_single:
        return False, "Exceeds maximum single withdrawal limit (₱100000.00)."
    if balance - amount < min_balance:
        return False, f"Insufficient remaining balance, must keep at least ₱{min_balance}.00."
    return True, "Withdrawal allowed."

print("Welcome to OtnisBank")
print("Please insert your card...")
time.sleep(5)
pwd = 1234
pin = int(input("Please enter your security pin: "))
bal = 737000
transaction_Num = 20221000114
while True:

    if pin == pwd:
        print("""
        ********************************************         
                    1) Balance
                    2) Withdraw
                    3) Deposit
                    4) Cancel Transaction       
        ********************************************        
             
            """)
        try:
            opt = int(input("Please choose your transaction "))
        except ValueError:
            print("Invalid input, input must be an integer.")
            continue

        if opt == 1:
            print(f"Your current balance is ₱{bal}.00")

        if opt == 2:
            print("Maximum of 100k per transaction | Minimum balance after withdrawal: ₱5000.00")
            try:
                withdraw = int(input("Please enter amount: "))
            except ValueError:
                print("Invalid input, amount must be an integer.")
                continue
            
            allowed, msg = can_withdraw(bal, withdraw)
            if not allowed:
                print(msg)
            else:
                bal -= withdraw
                print(f"₱{withdraw}.00 is withdrawn from your account...")
                print(f"Your updated balance is ₱{bal}.00")

        if opt == 3:
            try:
                deposit = int(input("How much money would you like to deposit?: "))
            except ValueError:
                print("Invalid input, amount must be an integer.")
                continue
            bal += deposit
            print(f"₱{deposit}.00 is deposited unto your account...")
            print(f"Your updated balance is ₱{bal}.00")

        if opt == 4:
            print("Transaction success...")
            print(f"Transaction number: {transaction_Num + 1}")
            print(
                "Thank you for choosing our bank. Invest in the red, it's in your best interest.")
            break
    else:
        print("Please enter a valid pin and try again.")
        break

二、余额低于5000的账户限制/注销逻辑 #

1. 账户交易限制 #

当余额低于5000时，限制取款操作，仅允许查询余额和存款：

# 在pin验证通过后增加余额检查
if pin == pwd:
    # 新增账户限制提示
    if bal < 5000:
        print("⚠️ NOTICE: Your account balance is below the minimum required (₱5000.00). Only balance inquiry and deposit are allowed.")
    
    # 原有菜单打印逻辑...
    
    # 在取款分支增加限制判断
    if opt == 2:
        if bal < 5000:
            print("Account restricted: Withdrawal is not allowed due to low balance.")
            continue
        # 原有取款校验逻辑...

2. 账户注销实现 #

模拟账户注销逻辑，当余额低于5000时提示用户，支持立即注销或触发自动注销规则：

import time

def can_withdraw(balance, amount, max_single=100000, min_balance=5000):
    if amount <= 0:
        return False, "Amount must be a positive integer."
    if amount > max_single:
        return False, "Exceeds maximum single withdrawal limit (₱100000.00)."
    if balance - amount < min_balance:
        return False, f"Insufficient remaining balance, must keep at least ₱{min_balance}.00."
    return True, "Withdrawal allowed."

print("Welcome to OtnisBank")
print("Please insert your card...")
time.sleep(5)
pwd = 1234
pin = int(input("Please enter your security pin: "))
bal = 737000
transaction_Num = 20221000114
account_active = True  # 新增账户状态标记

while True:
    if not account_active:
        print("Account has been closed. No transactions are allowed.")
        break
    
    if pin == pwd:
        # 余额低于5000时触发注销提示
        if bal < 5000:
            print("⚠️ WARNING: Your account balance is below ₱5000.00. Account will be automatically closed in 30 days if not replenished.")
            close_choice = input("Would you like to close your account immediately? (Y/N): ").strip().upper()
            if close_choice == 'Y':
                print(f"Account closed successfully. Your remaining balance ₱{bal}.00 will be issued as a paper check within 7 business days.")
                account_active = False
                bal = 0
                break
        
        print("""
        ********************************************         
                    1) Balance
                    2) Withdraw
                    3) Deposit
                    4) Cancel Transaction       
        ********************************************        
             
            """)
        try:
            opt = int(input("Please choose your transaction "))
        except ValueError:
            print("Invalid input, input must be an integer.")
            continue

        if opt == 1:
            print(f"Your current balance is ₱{bal}.00")

        if opt == 2:
            if bal < 5000:
                print("Account restricted: Withdrawal is not allowed due to low balance.")
                continue
            print("Maximum of 100k per transaction | Minimum balance after withdrawal: ₱5000.00")
            try:
                withdraw = int(input("Please enter amount: "))
            except ValueError:
                print("Invalid input, amount must be an integer.")
                continue
            
            allowed, msg = can_withdraw(bal, withdraw)
            if not allowed:
                print(msg)
            else:
                bal -= withdraw
                print(f"₱{withdraw}.00 is withdrawn from your account...")
                print(f"Your updated balance is ₱{bal}.00")

        if opt == 3:
            try:
                deposit = int(input("How much money would you like to deposit?: "))
            except ValueError:
                print("Invalid input, amount must be an integer.")
                continue
            bal += deposit
            print(f"₱{deposit}.00 is deposited unto your account...")
            print(f"Your updated balance is ₱{bal}.00")

        if opt == 4:
            print("Transaction success...")
            print(f"Transaction number: {transaction_Num + 1}")
            print(
                "Thank you for choosing our bank. Invest in the red, it's in your best interest.")
            break
    else:
        print("Please enter a valid pin and try again.")
        break

内容的提问来源于stack exchange，提问作者レッド・ スワン