How to fix this error of python tkinter StringVar?

Question

So basically i am going to write a program of python tkinter to show weight, however the variables and the objects are distracting me.

My code is like this:

from tkinter import *
import tkinter as tk

#object oriented BMI project
class Root(Tk):
    def __init__(self): 
        super(Root, self).__init__()


        #Info Bar
        self.title("Shushu BMI Calculator")
        self.geometry("1100x600")
        #self.resizable("False")
    
        #var
        self.weight = tk.StringVar()
        #self.w = tk.StringVar()

        #Caption
        self.caption = tk.Label(text = "BMI Calculator - Beta 2.0",
                             fg = "brown",
                             font="Arial 40")
        self.caption.grid(column = 0, row = 0, sticky = "N")

        #Copyright
        self.copyright = tk.Label(text = "Powered by Shushu Studio",
                                   fg = "green",
                                   font = "Arial 20")
        self.copyright.grid(column = 1, row = 0, sticky = "E")
    
        #Weight input Row
        self.weightInputTag = tk.Label(text="Please input your weight here (kg)")
        self.weightInputTag.grid(column = 0, row = 1, sticky = "W")

        self.weightEntry = tk.Entry(textvariable = self.weight)
        self.weightEntry.grid(column = 0, row = 1)
    
        self.weightSubmit = tk.Button(text="Submit",
                                     COMMAND=self.weightget)
        self.weightSubmit.grid(column = 0, row = 2)

        self.showWeight = tk.Label(text="")
        self.showWeight.grid(column = 0, row = 3)

        def weightget(self):
            weight = self.weightEntry.get()
            self.showWeight.configure(text=weight)


root = Root()
root.mainloop()

And the console show this:

Resetting Python state.
Running P:\2020\09\25\bmi.py
The interactive Python process has exited.
Traceback (most recent call last):
  File "P:\2020\09\25\bmi.py", line 52, in <module>
    root = Root()
  File "P:\2020\09\25\bmi.py", line 41, in __init__
    COMMAND=self.weightget)
  File "P:\Language\lib\tkinter\__init__.py", line 2345, in __getattr__
    return getattr(self.tk, attr)
AttributeError: '_tkinter.tkapp' object has no attribute 'weightget'

Please help, thanks very much!

Thingamabobs · Accepted Answer · 2020-09-25 14:14:21Z

The indention of your function was wrong.

def weightget(self):
    weight = self.weightEntry.get()
    self.showWeight.configure(text=weight)

If you want this function working as class method and not as a normal function in your local namespace of your class. Which I assume, since you put the parameter self in the function, then you need to make sure its on the right spot by the indentation.

import tkinter as tk
class Root(tk.Tk):
    def __init__(self): 
        super(Root, self).__init__()


        #Info Bar
        self.title("Shushu BMI Calculator")
        self.geometry("1100x600")
        #self.resizable("False")
    
        #var
        self.weight = tk.StringVar()
        #self.w = tk.StringVar()

        #Caption
        self.caption = tk.Label(text = "BMI Calculator - Beta 2.0",
                             fg = "brown",
                             font="Arial 40")
        self.caption.grid(column = 0, row = 0, sticky = "N")

        #Copyright
        self.copyright = tk.Label(text = "Powered by Shushu Studio",
                                   fg = "green",
                                   font = "Arial 20")
        self.copyright.grid(column = 1, row = 0, sticky = "E")
    
        #Weight input Row
        self.weightInputTag = tk.Label(text="Please input your weight here (kg)")
        self.weightInputTag.grid(column = 0, row = 1, sticky = "W")

        self.weightEntry = tk.Entry(textvariable = self.weight)
        self.weightEntry.grid(column = 0, row = 1)
    
        self.weightSubmit = tk.Button(self,text="Submit",
                                      command=self.weightget)
        self.weightSubmit.grid(column = 0, row = 2)

        self.showWeight = tk.Label(text="")
        self.showWeight.grid(column = 0, row = 3)

    def weightget(self):
        weight = self.weightEntry.get()
        self.showWeight.configure(text=weight)


root = Root()
root.mainloop()

Also the command argument in the OP code was COMMAND you changed this to command maybe keep a reference to that change, so OP dont get confused. Wouldnt be a problem if the OP copy-pastes your code, but ya

Pro Chess · Accepted Answer · 2020-09-25 14:31:16Z

from tkinter import *
import tkinter as tk

#object oriented BMI project
class Root(Tk):
    def __init__(self): 
        super(Root, self).__init__()

        def weightget(self):
            weight = self.weightEntry.get()
            self.showWeight.configure(text=weight)

        #Info Bar
        self.title("Shushu BMI Calculator")
        self.geometry("1100x600")
        #self.resizable("False")
    
        #var
        self.weight = tk.StringVar()
        #self.w = tk.StringVar()

        #Caption
        self.caption = tk.Label(text = "BMI Calculator - Beta 2.0",
                             fg = "brown",
                             font="Arial 40")
        self.caption.grid(column = 0, row = 0, sticky = "N")

        #Copyright
        self.copyright = tk.Label(text = "Powered by Shushu Studio",
                                   fg = "green",
                                   font = "Arial 20")
        self.copyright.grid(column = 1, row = 0, sticky = "E")
    
        #Weight input Row
        self.weightInputTag = tk.Label(text="Please input your weight here (kg)")
        self.weightInputTag.grid(column = 0, row = 1, sticky = "W")

        self.weightEntry = tk.Entry(textvariable = self.weight)
        self.weightEntry.grid(column = 0, row = 1)
    
        self.weightSubmit = tk.Button(text="Submit", command=lambda:weightget(self))
        self.weightSubmit.grid(column = 0, row = 2)

        self.showWeight = tk.Label(text="")
        self.showWeight.grid(column = 0, row = 3)

        


root = Root()
root.mainloop()

This works properly. Define the function before the process.

self.weightSubmit = tk.Button(text="Submit", command=lambda:weightget(self))

Give the command for the button like this as you are using object oriented programming. Make sure to use lambda

Read this https://www.w3schools.com/python/python_lambda.asp and you will get a better understanding about lambda

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