为什么我会收到错误消息：“NameError：未定义全局名称'pupiluserinputbox'”

Question

def pupiluserpass():
    global usernames, passwords
    usernameinp = pupiluserinputbox.get()
    passwordinp = pupilpasswordinputbox.get()

为什么会出现错误：NameError: global name 'pupiluserinputbox' 未定义？

输入框在另一个过程中：

def pupillogin():
   ruapupil = Label(app, text = "If you're a pupil log in here:")
   ruapupil.grid(row = 1, columnspan = 3, sticky = W)

   pupilusername = Label(app, text = "Please enter your Username:")
   pupilusername.grid(row = 2, column = 0, sticky = W)
   pupiluserinputbox = Entry(app, width = 10)
   pupiluserinputbox.grid(row = 2, column = 1, sticky = W)

   pupilpassword = Label(app, text = "Please enter your Password:")
   pupilpassword.grid(row = 3, column = 0, sticky = W)
   pupilpasswordinputbox = Entry(app, width = 10)
   pupilpasswordinputbox.grid(row = 3, column = 1, sticky = W)

   pupilenter = Button(app, text = "Enter!", command = pupiluserpass)
   pupilenter.config(height = 1, width = 8)
   pupilenter.grid(row = 4, column = 1, sticky = W) 

我怎样才能成功地完成这项工作而不得到NameError？

Answer 1

对于class，您应该将携带这些错误属性的变量设置为self，即该对象的当前实例。这是在class 中的其他方法中访问这些变量的事实上的方式。例如：

def pupiluserpass():
    ...
    usernameinp = self.pupiluserinbox.get()
    passwordinp = self.pupilpasswordinputbox.get()

def pupillogin():
    ...
    self.pupiluserinputbox = Entry(app, width = 10)
    self.pupiluserinputbox.grid(row = 2, column = 1, sticky = W)
    ...
    self.pupilpasswordinputbox = Entry(app, width = 10)
    self.pupilpasswordinputbox.grid(row = 3, column = 1, sticky = W)

你也可以在这里做很多global声明，但最好使用self。