how can I use the variable from class A in class B (python)-CodePudding

I want to use the variable (file) in class (PageOne) I'm not good in python so even when I did my research I couldn't do it, can you help me please ? My project is to take a csv file from the user(in WelcomePage) and it will pick a random row from that file and show it in (PageOne).

i tried different ways but always the same error message (name 'file' is not defined)

from cProfile import label
import tkinter as tk
from turtle import title
from typing import Container
from tkinter import font as tkfont
from tkinter.filedialog import askopenfile 


class MainFrame (tk.Tk):




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

       self.titlefont = tkfont.Font(family = 'Verdana',size=12,
                                   weight = "bold", slant='roman')

       container =tk.Frame()
       container.grid(row=0, column=0, sticky='nesw')

       self.id =tk.StringVar()
       self.id.set("Mister")

       self.listing = {}

       for p in (WelcomePage, PageOne):
           page_name = p.__name__
           frame = p(parent = container, controller = self)
           frame.grid(row=0, column=0, sticky='nesw')
           self.listing[page_name] = frame

       self.up_frame('WelcomePage')

   def up_frame(self,page_name):
       page = self.listing[page_name]
       page.tkraise()

class WelcomePage(tk.Frame):
   global file
   def open_file():
       
       file = askopenfile(mode='r', filetypes=[('I', '*csv')])
       if file is not None:
           pass
       return file

   def __init__(self, parent, controller):
       tk.Frame.__init__(self, parent)
       self.controller = controller
       self.id = controller.id

       label = tk.Label(self,text= "Welcome Page \n"  controller.id.get(),
                        font= controller.titlefont)
       label.pack()
       lod = tk.Button (self, text="Select a file",
                        command= lambda:open_file())
       lod.pack()
       bou = tk.Button (self, text="Submit",
                        command= lambda: controller.up_frame("PageOne"))
       bou.pack()
       
   






class PageOne(WelcomePage,tk.Frame):
   def __init__(self, parent, controller):
       tk.Frame.__init__(self, parent)
       self.controller = controller
       self.id = controller.id

       label = tk.Label(self,text= "Page One \n"  controller.id.get(),
                        font= controller.titlefont)
       label.pack()

       bou = tk.Button (self, text="back to main",
                        command= lambda: controller.up_frame("WelcomePage"))
       bou.pack()
       
       
       

       

if __name__ == '__main__':
   app = MainFrame()
   app.mainloop()

CodePudding user response：

try this -- use the keyword global in the method as well for the variable purpose

then your error of file name is not defined should resolved.

   def open_file():
   global file
   file = askopenfile(mode='r', filetypes=[('I', '*csv')])
   if file is not None:
       pass
   return file

CodePudding user response：

In Python 3.8 used Walrus. Put keyword inside function

Before:

   def open_file():       
       file = askopenfile(mode='r', filetypes=[('I', '*csv')])
       if file is not None:
           pass
       return file

After Walrus:

def open_file():
    global file
    if (file := askopenfile(mode='r', filetypes=[('I', '*py' is not None)])):
       pass
    return file