NameError：名字“clear_message”没有定义

Question

from Tkinter import * 
import tkinter as tk # python3 

TITLE_FONT = ("Helvetica", 18, "bold") 


class SampleApp(tk.Tk): 

    def __init__(self, *args, **kwargs): 
     tk.Tk.__init__(self, *args, **kwargs) 

     # the container is where I stack a bunch of frames 
     # on top of each other, then the one we want visible 
     # will be raised above the others 
     container = tk.Frame(self) 
     container.pack(side="top", fill="both", expand=True) 
     container.grid_rowconfigure(0, weight=1) 
     container.grid_columnconfigure(0, weight=1) 

     self.frames = {} 
     for F in (MainPage,StorageOrMotor,Storage,Motor): 
      page_name = F.__name__ 
      frame = F(container, self) 
      self.frames[page_name] = frame 

      # put all of the pages in the same location; 
      # the one on the top of the stacking order 
      # will be the one that is visible. 
      frame.grid(row=0, column=0, sticky="nsew") 

     self.show_frame("MainPage") 

    def show_frame(self, page_name): 
     '''Show a frame for the given page name''' 
     frame = self.frames[page_name] 
     frame.tkraise() 


class MainPage(tk.Frame): 

    global user_key 
    global psw_key 
    user_key="" 
    psw_key="" 

#Here is the defined for clear_message `def` 
    def clear_message(): 
     user_key.delete(0, 'END') 
     psw_key.delete(0, 'END') 

    def __init__(self, parent, controller): 
     tk.Frame.__init__(self, parent) 
     self.controller = controller 
     Username = tk.Label(self, text="Username:",font=("Helvetica", "20","bold")) 
     Username.grid(row=2, column=3,columnspan=2) 
     Password = tk.Label(self, text="Password:",font=("Helvetica", "20","bold")) 
     Password.grid(row=3, column=3,columnspan=2) 

#............   
     Username_key = tk.Entry(self, textvariable = user_key, width=19, font=("Helvetica", "15")) 
     Username_key.grid(row=2, column=5,columnspan=5) 
     Password_key = tk.Entry(self, textvariable = psw_key, width=19, font=("Helvetica", "15")) 
     Password_key.grid(row=3, column=5,columnspan=5) 
     log_in = tk.Button(self, width=7, text="Log In", command=lambda: controller.show_frame("StorageOrMotor")) 
     log_in.grid(row=5,column=8,columnspan=2) 
#............`I try to create a clear button` 
     Clear = tk.Button(self, width=7, text=" Clear " ,command=lambda:clear_message()) 
     Clear.grid(row=5,column=5,columnspan=2) 

Answer 1

clear_message()属于MainPage类，以便类中调用它时，你需要使用self.前缀。另外，由于定义方法是类的成员，因此需要使用self作为参数。

def clear_message(self): #self here 
    user_key.delete(0, 'END') 
    psw_key.delete(0, 'END') 

此外，由于clear_message不带任何参数，所以不需要lambda表达式。

#self here and removed lambda 
Clear = tk.Button(self, width=7, text=" Clear " ,command=self.clear_message)