[Tutor] Python ConfigParser Tkinter update configuration file between modules

[Niro One]

I have two Tkinter windows main and configuration. Main window provides button link to configuration. In configuration main window editable. Configuration window provides button link for main window return. Configuration edit successful at Sypder IDE print. Configuration edit successful at write to disk. Returning to main window, configuration update FAIL. 

Close/restart main update PASS. Close/restart configuration update PASS.
Changing 'r' to 'r+' at read_file wipes out configuration write.
Thanks for having a look!

'''mdf.py'''
import os
import sysimport cnfimport tkinter as tk
from configparser import ConfigParser
config = ConfigParser(allow_no_value=True)
cfg_key = 0
if os.path.isfile('ini.ini') and os.access('ini.ini', os.R_OK):    try:        with open ('ini.ini', 'r') as cfg:            config.read_file(cfg)            print (config.sections())                        """[ins_exe]"""            ins_exe = config.get('ins_exe', 'ins_exe')
            cfg.close()      except:        cfg_key = 1        print ("INI_ERR")        print ()
else:    cfg_key = 1    print ("INI_BAK")    print ()
if cfg_key == 1:    print ("INI_SET")    print ()
    """[ins_exe]"""    ins_exe = '0'
class Application(tk.Frame):    def __init__(self, *args, **kwargs):        super().__init__(*args, **kwargs)        self.GetChk()
    def GetChk(self):        lbl_mdf = tk.StringVar()        lbl_mdf = tk.Label(self.master, text='mdf_exe')        lbl_mdf.place(x=35, y=15)        global ent_mdf        ent_mdf = tk.StringVar()        ent_mdf = tk.Entry(self.master, width=10, justify=tk.CENTER)        ent_mdf.place(x=25, y=40)        ent_mdf.insert(0, (ins_exe))        rtn_cnf = tk.Button(self.master, text='cnf_fmt', width=10,                            command=self.CnfOpn)        rtn_cnf.place(x=115, y=20)        run = tk.Button(self.master, text='mdf_exe', width=10,                        command=self.ChkOut)        run.place(x=115, y=55)        def ChkOut(self):        print ('mdf_exe =', ent_mdf.get())        self.FileOpn()        def CnfOpn(self, *args):        print ('mdf_cfg')        ask_cfg = tk.messagebox.askokcancel('mdf', " proceed cnf_fmt ? ")        if ask_cfg == True:            self.master.destroy()            cnf.CreateConfiguration()        else:            pass        def FileOpn(self):        stdoutOrigin=sys.stdout         sys.stdout = open('MAIN.txt', 'w')        print ("%")        print ()        print ('mdf_exe =', ent_mdf.get())        print ()        print ("%")        sys.stdout.close()        sys.stdout=stdoutOrigin
def CreateApplication():    root = tk.Tk()    root.title('mdf')    root.geometry('210x100+125+250')    root.resizable(0,0)    app = Application(root)    app.mainloop()    if __name__ == "__main__":    CreateApplication()

'''cnf.py'''
import osimport mdfimport tkinter as tk
from configparser import ConfigParser
config = ConfigParser(allow_no_value=True)
cfg_key = 0
if os.path.isfile('ini.ini') and os.access('ini.ini', os.R_OK):    try:        with open ('ini.ini', 'r') as cfg:            config.read_file(cfg)            print (config.sections())                        """[ins_exe]"""            ins_exe = config.get('ins_exe', 'ins_exe')
            cfg.close()        except:        cfg_key = 1        print ("INI_ERR")        print ()
else:    cfg_key = 1    print ("INI_BAK")    print ()
if cfg_key == 1:        print ("INI_SET")    print ()
    """[ins_exe]"""    ins_exe = '0'
class Configuration(tk.Frame):    def __init__(self, *args, **kwargs):        super().__init__(*args, **kwargs)        self.GetChk()
    def GetChk(self):
        lbl_cnf = tk.StringVar()        lbl_cnf = tk.Label(self.master, text='cnf_fmt')        lbl_cnf.place(x=35, y=15)        global ent_cnf        ent_cnf = tk.StringVar()        ent_cnf = tk.Entry(self.master, width=10, justify=tk.CENTER)        ent_cnf.place(x=25, y=40)        ent_cnf.insert(0, (ins_exe))        rtn_mdf = tk.Button(self.master, text='mdf_exe', width=10,                            command=self.MdfOpn)        rtn_mdf.place(x=115, y=20)        run = tk.Button(self.master, text='cnf_fmt', width=10,                        command=self.ChkOut)        run.place(x=115, y=55)        def ChkOut(self):        print ('cnf_fmt =', ent_cnf.get())        self.FileOpn()
    def MdfOpn(self, *args):        print ('mdf_cfg')        ask_cfg = tk.messagebox.askokcancel('cnf', " proceed mdf_exe ? ")        if ask_cfg == True:            self.master.destroy()            mdf.CreateApplication()        else:            pass
    def FileOpn(self):                ins_exe =  ent_cnf.get()                config['ins_exe'] = {                'ins_exe' : ins_exe,                }                        with open('ini.ini', 'w+') as cfg:            print ('cnf_fmt = ini_w+')            config.write(cfg)            cfg.close()
def CreateConfiguration():    root = tk.Tk()    root.title('cnf')    root.geometry('210x100+300+300')    root.resizable(0,0)    app = Configuration(root)    app.mainloop()    if __name__ == "__main__":    CreateConfiguration()