[FIXED] How Do I assign a function to a button in Python/TKinter?

Issue

I am fairly new to TKinter and have been trying to convert my normal Python code into a GUI (TKinter Code)! I have been working on this code and so far, I have got the basic layout made but I am having problems coding buttons and using entries. You will most likely find a lot of errors in my code so be warned! :D

I have got an entry at the top of the window and I want the user to input a number into the entry and then I want to use the text inputted in the entry in some code (btn1()). I also want the user to press a button and then the button to run some code with labels underneath where the buttons are showing the results of the code (the labels in the btn1() function).

First, I want the user to input a number into the entry. Then, I want the user to click on a button which is underneath the entry. Finally, I want the results of the code behind the button, to be show underneath the buttons (in labels!).

Here is my code:

from tkinter import *

class window_design:

def __init__(self):
    root=Tk()
    root.title("Bag Weight")
    root.geometry("500x700")
    root.wm_iconbitmap('favicon.ico')


    image=PhotoImage(file="Weight Program.png")
    imagelabel=Label(root,image=image)
    imagelabel.pack()


    weightentrylabel=Label(root,text="Enter Weight!")
    weightentrylabel.pack()

    self.string=StringVar()
    weightentry=Entry(root,textvariable=self.string)
    weightentry.pack()

    menutext=Label(root,text="What coin are you using?")
    menutext.pack(side=LEFT)

    values=['1p','2p','5p','10p','20p','50p','£1','£2','Exit']

    def btn1(self,btn1code):
        p1=3.56
        p1should=356
        if (self.string.get()) > p1should:
            weightdif=(self.string.get())-p1should
            coins=weightdif/p1
            labeldif=Label(text=weightdif)
            labelcoins=Label(text=coins)
        elif (self.string.get()) < p1should:
            weightdif=p1should-(self.string.get())
            coins=weightdif/p1
            labeldif=Label(text=weightdif)
            labelcoins=Label(text=coins)

    button1=Button(root,text="1p",command=btn1)
    button1.pack(side=LEFT)



    root.mainloop()



window_design()

I am currently getting this error:

Exception in Tkinter callback
Traceback (most recent call last):
  File "C:\Users\cjay2\AppData\Local\Programs\Python\Python35-32\lib\tkinter\__init__.py", line 1549, in __call__
    return self.func(*args)
TypeError: btn1() missing 2 required positional arguments: 'self' and 'btn1code'

Solution

You should use self.btn1 ( btn1 is a class method) in button1=Button(root,text="1p",command=btn1).

btn1() is called with one argument and it needs two arguments, set a default value to btn1code or removeit (if you do not use it).

When you call get() method on StringVar() it will return a string so you need to convert before comparing with integers.

To show result in label use a self.result = StringVar() then call self.result.set(a_string). Check the following code:

from tkinter import *

class window_design:

    def __init__(self):
        root=Tk()
        root.title("Bag Weight")
        #root.geometry("500x700")
        root.wm_iconbitmap('favicon.ico')


        image=PhotoImage(file="Weight Program.png")
        imagelabel=Label(root,image=image)
        imagelabel.pack()


        weightentrylabel=Label(root,text="Enter Weight!")
        weightentrylabel.pack()

        self.string=StringVar()
        weightentry=Entry(root,textvariable=self.string)
        weightentry.pack()

        menutext=Label(root,text="What coin are you using?")
        #menutext.pack(side=LEFT)
        menutext.pack()

        values=['1p','2p','5p','10p','20p','50p','£1','£2','Exit']

        button1=Button(root,text="1p",command=self.btn1)
        #button1.pack(side=LEFT)
        button1.pack()

        #--------------------------------------------------
        self.result=StringVar()
        resultlabel=Label(root, textvariable = self.result)
        resultlabel.pack()
        #--------------------------------------------------

        root.mainloop()
    #-------------------------------------  
    def btn1(self):
        p1=3.56
        p1should=356
        if not self.string.get(): return

        value = int(self.string.get())
        if value > p1should:
            weightdif = value - p1should
            coins=weightdif/p1

        elif value < p1should:
            weightdif=p1should - value
            coins=weightdif/p1

        self.result.set(coins)
    #-----------------------------------



window_design()

Answered By - Kenly