关于类和tkinter user_reg（）缺少1个必需的位置参数：“ self”

Question

我在这里做错了什么？ 我正试图从__init__ var - self.username_entry 但是python总是说：user_reg() missing 1 required positional argument: 'self'

class Register_user:

    def __init__(self):
        root = Tk()
        root.geometry("300x250")
        root.title("Games V1.0")
        self.username = StringVar()
        self.password = StringVar()
        root.label1 = Label(root, text="Nickname ").pack()
        root.emlabel = Label(root, text="").pack()
        self.username_entry= Entry(root, textvariable=username)
        self.username_entry.pack()
        root.emlabel = Label(root, text="").pack()
        root.label2 = Label(root, text="Password*").pack()
        self.password_entry = Entry(root, show='*', textvariable=password)
        self.password_entry.pack()
        self.bt1 = Button(root, text="Register", width=10, height=1, command=self.user_reg).pack()
        root.mainloop()

    def user_reg(self):  # Register the user only if the nickname avilible
        username = self.username_entry
        password = self.password_entry
        list_of_files = os.listdir()  # list of files on the directory
        if username in list_of_files:
            reg_failed_user(self)
            username.delete(0, END)
            password.delete(0, END)
        else:
            file = open(username, "w")
            file.write(password)
            self.username_entry.delete(0, END)
            self.password_entry.delete(0, END)
            reg_success(self)

    def reg_failed_user(self):
        pass

    def reg_success(self):
        pass