我试图创建一个registerFunction将用户名和密码保存到列表中。但是，当我在while循环中调用username_list（位于readFunction中）时，收到错误消息“未定义username_list”
def readFunction(): #--------------------------------------------------readFunction
username_read = open('username_db.csv', 'r')
global username_list
username_list = [n.replace("\n","") for n in username_read.readlines()]#<<<-------------------------Where the variable is created is produced
username_read.close()
password_read = open('password_db.csv', 'r')
global password_list
password_list = [n.replace("\n", "") for n in password_read.readlines()]
password_read.close()
def registerFunction(): #----------------------------------------------registerFunction
print("\nRegister - Please enter your details below\n")
username = input("Enter a Username: ")
password = input("Enter a Password: ")
passwordConfirm = input("Confirm your password: ")
while username in username_list: #<<<-------------------------Where the error is produced
print("Sorry, this username is already in use")
username = input("Enter a Username: ")
else:
username_list.append(username)
password_list.append(password)
print("Your account has been successfully created")
