python tkinter.Radiobutton can't get value - python-3.x

Question

I'm writing a python code with tkinter (python3) but I have some problems. I have two classes _MainScreen and _RegisterScreen (this last is nested in _MainScreen). In _RegisterScreen I had implemented a simple question with tkinter.Radiobutton (choose your sex: male, female). The idea is to catch the user selection, but when I run the script, the value assigned to the variable is empty (""). However, if I run the class _RegisterScreen alone, it works. I hope you can show me where is my error. Thanks in advance.
Here is an abstraction (32 lines) of my code (250 lines):
import tkinter
class _MainScreen(tkinter.Frame):
def __init__(self):
self.root = tkinter.Tk()
self.new_account(self.root)
self.root.mainloop()
def new_account(self, frame):
tkinter.Button(frame, text="Create new account",
command=self.create_new_account).pack(anchor="center", pady=(0,15))
def create_new_account(self):
_RegisterScreen()
class _RegisterScreen(tkinter.Frame):
def __init__(self):
self.root = tkinter.Tk()
tkinter.Label(self.root, text="Sex").grid(row=1, padx=(0,10), sticky="w")
self.sex_option = tkinter.StringVar()
tkinter.Radiobutton(self.root, text="Male", variable=self.sex_option,
value="Male", command=self._selected).grid(row=1, column=1)
tkinter.Radiobutton(self.root, text="Female", variable=self.sex_option,
value="Female", command=self._selected).grid(row=1, column=2)
tkinter.Button(self.root, text="Submit",
command=self._login_btn_clickked).grid(row=3, columnspan=4, pady=20)
self.root.mainloop()
def _login_btn_clickked(self):
sex = self._selected()
print(sex)
def _selected(self):
return self.sex_option.get()
_MainScreen()
#_RegisterScreen() # comment the above line and uncomment this line
# to test the _RegisterScreen object alone.

Answer 1

After doing some research on how tkinter's RadioButton widget works, I believe I have a solution to your problem:
Here's your new _RegisterScreen function:
class _RegisterScreen(tkinter.Frame):
def __init__(self):
self.gender = "NA" #Variable to be changed upon user selection
self.root = tkinter.Tk()
tkinter.Label(self.root, text="Sex").grid(row=1, padx=(0,10), sticky="w")
self.sex_option = tkinter.StringVar()
#This Radiobutton runs the setMale function when pressed
tkinter.Radiobutton(self.root, text="Male", variable=self.sex_option,
value="Male", command=self.setMale).grid(row=1, column=1)
#This Radiobutton runs the setFemale function when pressed
tkinter.Radiobutton(self.root, text="Female", variable=self.sex_option,
value="Female", command=self.setFemale).grid(row=1, column=2)
tkinter.Button(self.root, text="Submit",
command=self._login_btn_clickked).grid(row=3, columnspan=4, pady=20)
self.root.mainloop()
def _login_btn_clickked(self):
sex = self.gender #gets the value stored in gender and assigns it to sex
print(sex)
def setMale(self):
self.gender="Male" #sets gender to Male
def setFemale(self):
self.gender="Female" #sets gender to Female
Ultimately, you want to run 2 separate functions for either RadioButton.
When the Male Radiobutton gets clicked, it runs the setMale function.
When the Female Radiobutton gets clicked, it runs the setFemale function.
I believe you were confused about what RadioButton's variable and value attributes actually are (as was I before looking further into this).
I learned more about what those those do in this video: https://www.youtube.com/watch?v=XNF-y0QFNcM
I hope this helps! ~Gunner