尝试从 python 中的另一个 class 访问 StringVar 时出现 AttributeError

Question

So I've been working on a Personal Training App in python I have a Start Up window, referenced in the code as StartUp. Once the user enters the name of the client that they want to see records for, I'm trying to get the name variable from the StartUp class to the Application class. However, when I run it, it gives me the following error

Traceback (most recent call last):
File "/usr/lib/python3.6/tkinter/__init__.py", line 1705, in __call__
return self.func(*args)
File "/home/ninja65/PtApp/main.py", line 32, in <lambda>
old = tk.Button(mainframe, text='Open', command=lambda:[parent.destroy(), Workspace()],bg='sienna3')
File "/home/ninja65/PtApp/main.py", line 16, in Workspace
App = Application(root)
File "/home/ninja65/PtApp/main.py", line 55, in __init__
self.target = StartUp.target
AttributeError: type object 'StartUp' has no attribute 'target'

the Code is below

# !usr/bin/python3
import tkinter as tk
import json

def CreateNew():
  temp = tk.Tk()
  temp.title('Enter New Client')
  New = MakeNew(temp)
  temp.eval('tk::PlaceWindow . center')
  temp.mainloop()

def Workspace():
  root = tk.Tk()
  root.config(bg='grey9')
  root.title("Personal Trainer")
  App = Application(root)
  root.eval('tk::PlaceWindow . center')
  root.mainloop()

class StartUp():
  def __init__(self, parent):    
    mainframe = tk.Frame(parent, bg='firebrick4')
    mainframe.grid(column=0, row=0, sticky=tk.N)
    # Adding widgets to the frame
    opening = tk.Label(mainframe, text='Welcome, what do you want to do?', font='tahoma', bg='firebrick4', fg='khaki3')
    guide = tk.Label(mainframe, text="Type the Client's name with no gaps", font='tahoma', bg='firebrick4', fg='khaki3')
    guide.grid(columnspan=10, row=1)
    opening.grid(columnspan=10, row=0, pady=5, padx=5)
    self.target = tk.StringVar()
    open_entry = tk.Entry(mainframe, textvariable=self.target)
    open_entry.grid(columnspan=7, row=2, sticky=tk.W+tk.E, padx=5)
    old = tk.Button(mainframe, text='Open', command=lambda:[parent.destroy(), Workspace()], bg='sienna3')
    old.grid(column=7, columnspan=4, row=2, sticky=tk.W+tk.E, pady=5, padx=5)
    new = tk.Button(mainframe, text='New Client', command=lambda:[parent.destroy(), CreateNew()], bg='sienna3', font='tahoma')
    new.grid(columnspan=10, row=3, sticky=tk.W+tk.E, pady=5, padx=5)


class MakeNew:

def __init__(self, loader):
    menubutton = tk.Menubutton(loader, text = "File")
    menubutton.grid()
    menubutton.menu = tk.Menu(menubutton)
    menubutton["menu"]=menubutton.menu
    menubutton.menu.add_checkbutton(label = "New file")
    menubutton.menu.add_checkbutton(label = "Save")
    menubutton.menu.add_checkbutton(label = "Save as")
    menubutton.pack()

def method(self):
    pass

class Application(StartUp):
  def __init__(self, master):
    self.target = StartUp.target
    menubutton = tk.Menubutton(master, text = "File",font='gothic', bg='#86C232')
    menubutton.grid(column=0, row=0, sticky=tk.W+tk.E)
    menubutton.menu = tk.Menu(menubutton, bg='#86C232')
    menubutton["menu"]=menubutton.menu
    menubutton.menu.add_checkbutton(label = "New file")
    menubutton.menu.add_checkbutton(label = "Save")
    menubutton.menu.add_checkbutton(label = "Save as")
    # Frame of vital info
    v_frame = tk.Frame(master, bg='gray16')
    v_frame.grid(column=0, row=1, sticky=tk.W+tk.E)
    # Frame of Additional info
    a_frame = tk.Frame(v_frame)
    a_frame.grid(column=5, row=0, sticky=tk.E+tk.W+tk.N)
    # Frame of Exercise routine
    e_frame = tk.Frame(master, bg='grey18')
    e_frame.grid(column=0, row=2, sticky=tk.S)
    # First Row of Vital Info
    cl_name = tk.Label(v_frame, text=self.target, bg='gray15', fg='#61892F',font='tahoma').grid(column=0, row=0, sticky=tk.W+tk.E)
    cl_age = tk.Label(v_frame, text='Age', bg='gray15', fg='#61892F',font='tahoma').grid(column=1, row=0, sticky=tk.W+tk.E)
    cl_height = tk.Label(v_frame, text='Height', bg='gray15', fg='#61892F',font='tahoma').grid(column=2, row=0, sticky=tk.W+tk.E)
    cl_weight = tk.Label(v_frame, text='Weight', bg='gray15', fg='#61892F',font='tahoma').grid(column=3, row=0, sticky=tk.W+tk.E)
    cl_sex = tk.Label(v_frame, text='Gender', bg='gray15', fg='#61892F',font='tahoma').grid(column=4, row=0, sticky=tk.W+tk.E)
    # Second Row of Vital Info
    cl_bfp = tk.Label(v_frame, text='Fat %', bg='gray15', fg='#61892F',font='tahoma').grid(column=0, row=1, sticky=tk.W+tk.E)
    cl_lbm = tk.Label(v_frame, text='Lean Mass', bg='gray15', fg='#61892F',font='tahoma').grid(column=1, row=1, sticky=tk.W+tk.E)
    cl_gw = tk.Label(v_frame, text='Goal Weight', bg='gray15', fg='#61892F',font='tahoma').grid(column=2, row=1, sticky=tk.W+tk.E)
    cl_bmi = tk.Label(v_frame, text='BMI', bg='gray15', fg='#61892F',font='tahoma').grid(column=3, row=1, sticky=tk.W+tk.E)
    # Last Row
    cl_goal = tk.Label(v_frame, text='Goals that the client put go here', bg='gray15', fg='#61892F',font='tahoma').grid(columnspan=5, row=2, sticky=tk.W+tk.E)
    # Additional Column
    atest = tk.Label(a_frame, text='Test', bg='gray22').grid(column=0, row=0)
    # Exercise Routine Column
    mday_label = tk.Label(e_frame, text='Monday', bg='gray18', fg='#61892F', font='gothic').grid(column=0, row=0)
    tday_label = tk.Label(e_frame, text='Tuesday', bg='gray18', fg='#61892F', font='gothic').grid(column=1, row=0)
    wday_label = tk.Label(e_frame, text='Wednesday', bg='gray18', fg='#61892F', font='gothic').grid(column=2, row=0)
    thday_label = tk.Label(e_frame, text='Thursday', bg='gray18', fg='#61892F', font='gothic').grid(column=3, row=0)
    fday_label = tk.Label(e_frame, text='Friday', bg='gray18', fg='#61892F', font='gothic').grid(column=4, row=0)
    saday_label = tk.Label(e_frame, text='Saturday', bg='gray18', fg='#61892F', font='gothic').grid(column=5, row=0)
    sday_label = tk.Label(e_frame, text='Sunday', bg='gray18', fg='#61892F', font='gothic').grid(column=6, row=0)
    mday = tk.Listbox(e_frame, bg='gray22').grid(column=0, row=1)
    tday = tk.Listbox(e_frame, bg='gray22').grid(column=1, row=1)
    wday = tk.Listbox(e_frame, bg='gray22').grid(column=2, row=1)
    thday = tk.Listbox(e_frame, bg='gray22').grid(column=3, row=1)
    fday = tk.Listbox(e_frame, bg='gray22').grid(column=4, row=1)
    stday = tk.Listbox(e_frame, bg='gray22').grid(column=5, row=1)
    sday = tk.Listbox(e_frame, bg='gray22').grid(column=6, row=1)

def method(self):
    pass

if __name__ == '__main__':
  sub = tk.Tk()
  sub.config(bg='firebrick4')
  sub.title('PT App Login')
  Window = StartUp(sub)
  sub.eval('tk::PlaceWindow . center')
  sub.mainloop()

Answer 1

I see at least two problems. For one, you are trying to reference Startup.target , which is a reference to a class variable. You haven't defined a class variable named target . You have instead defined an instance variable named target.

Also, your Application inherits from Startup but it does not call the __init__ method of Startup so the object is incorrectly initialized. Since Application inherits from Startup , it should be initialized like this:

class Application(StartUp):
  def __init__(self, master):
    super().__init__(master)
    ...

Once you do that, there's no reason to do self.target = Startup.target since self.target already exists.

There are other bugs in the code, but this explains the error your question is asking about and how to fix that specific error.