accessing entry widget via get

Question

I want to access the entry widget via the get() method, not the variable. The problem is I can´t seem to make the entry as variable accessible in other methods. The widget I am talking about is the trennzeichenentry widget from my menubaroptions method. Here is a snippet of my code:

import tkinter
from tkinter.constants import *
from tkinter import messagebox
from struct import unpack
from codecs import decode

class Graphicaluserinterface(tkinter.Frame):

    @classmethod
    def main(cls):
        root = tkinter.Tk()
        root.title('Hex2Dec_Converter_APS300')
        root.minsize(560, 105)
        gui = cls(root)
        gui.grid(row=0, column=0, sticky=NSEW)
        root.grid_rowconfigure(0, weight=1)
        root.grid_columnconfigure(0, weight=1)
        root['menu'] = gui.menubar
        root.mainloop()

    def __init__(self, master=None):
        super().__init__(master)
        for rowconfigure in range(5):
            self.master.grid_rowconfigure(rowconfigure,weight=1)
        for columnconfigure in range(4):
            self.master.grid_columnconfigure(columnconfigure,weight=1)
        frame1 = tkinter.Frame(master)
        frame1.grid(row=0,column=0,rowspan=5,columnspan=1,sticky=NSEW)
        frame1.columnconfigure(0,weight=1)
        frame2 = tkinter.Frame(master)
        frame2.grid(row=0,column=1,rowspan=5,columnspan=3,sticky=NSEW)
        frame2.columnconfigure(1,weight=2)
        frame2.rowconfigure(0,weight=0)
        frame2.rowconfigure(1,weight=6)
        frame2.rowconfigure(2,weight=0)
        frame2.rowconfigure(3,weight=1)
        frame2.rowconfigure(4,weight=2)
        self.entrystring = tkinter.IntVar()
        self.taktzykluszeit = tkinter.DoubleVar()
        self.menubar = tkinter.Menu(self)
        self.file_menu = tkinter.Menu(self.menubar, tearoff=FALSE)
        self.help_menu = tkinter.Menu(self.menubar, tearoff=FALSE)
        self.create_widgets()

    def create_widgets(self):
        self.menubar.add_cascade(label="File", menu=self.file_menu)
       self.file_menu.add_command(label="Options",command=self.menubaroptions)

    def menubaroptions(root):
        optionswindow = tkinter.Toplevel(root)
        optionswindow.title("Options")
        optionswindow.minsize(300,150)
        trennzeichenlabel = tkinter.Label(optionswindow,text="Length of Separator in Byte:")
        trennzeichenlabel.pack()
        trennzeichenentry = tkinter.Entry(optionswindow,textvariable=root.entrystring,width=30,justify="center")
        trennzeichenentry.pack()
        taktzykluszeitlabel = tkinter.Label(optionswindow,text="Measurementtime for all \n Temperature-Sensors in sec")
        taktzykluszeitlabel.pack()
        taktzykluszeitentry = tkinter.Entry(optionswindow,textvariable=root.taktzykluszeit,width=30,justify="center")
        taktzykluszeitentry.pack()

    def methodiwanttocallthevariablein(self):
        #call trennzeichenentry here

if __name__ == '__main__':
    Graphicaluserinterface.main()

So how can I make "trennzeichenentry" into a variable and call it in the method "methodiwanttocallthevariablein" ? I always got NameError when trying around myself. I am not quite sure what is different here than to my other methods and variable I have.

Answer 1

When defining a variable inside of a function if you do not use global then the function will assume you want to assign that variable locally only. This will basically mean that nothing else in your code can access that variable unless you mark it as global or pass it directly to another function.

So add this:

global trennzeichenentry

In the menubaroptions function like this:

def menubaroptions(root):
     global trennzeichenentry

You will also need to define the global in your other method as well. All that said you really don't want to use global in a class and your class should be reworked to compensate for this properly.

Here is a simplified version of your code that shows how to set up your entry fields as a class attribute so you can avoid global variables.

import tkinter as tk


class GraphicalUserInterface(tk.Tk):
    def __init__(self):
        super().__init__()
        self.minsize(560, 105)
        self.entry_string = tk.IntVar()
        self.taktzykluszeit = tk.DoubleVar()
        self.menubar_options()
        tk.Button(self, text='print entries', command=self.method_i_want_to_call_the_variable_in).grid()

    def menubar_options(self):
        optionswindow = tk.Toplevel(self)
        optionswindow.minsize(300, 150)
        tk.Label(optionswindow, text="Length of Separator in Byte:").pack()
        self.trennzeichenentry = tk.Entry(optionswindow, textvariable=self.entry_string, width=30, justify="center")
        self.trennzeichenentry.pack()
        tk.Label(optionswindow, text="Measurementtime for all \n Temperature-Sensors in sec").pack()
        self.taktzykluszeitentry = tk.Entry(optionswindow, textvariable=self.taktzykluszeit, width=30, justify="center")
        self.taktzykluszeitentry.pack()

    def method_i_want_to_call_the_variable_in(self):
        print(self.trennzeichenentry.get())
        print(self.taktzykluszeitentry.get())

if __name__ == '__main__':
    GraphicalUserInterface().mainloop()