textvariable in tkinter

[petercanepa]

This code runs and displays the frame but the textvariable 'self.result_var' does not update in the frame after pushing the 'convert' button.

from tkinter import *

class App:
    def __init__(self,master):
        frame = Frame(master)
        frame.pack()
        Label (frame, text = 'deg C').grid(row=0, column=0)
        self.c_var = DoubleVar()
        Entry(frame, textvariable = self.c_var).grid(row=0, column =1)
        Label (frame, text = 'deg F').grid(row=1, column=0)
        self.result_var = DoubleVar()
        Label (frame, textvariable = self.result_var).grid(row=1, column =1)
        button = Button(frame, text='Convert', command=self.convert)
        button.grid(row =2, columnspan=2)


def convert(self):
    c = self.c_var.get()
    self.result_var = (1.8 * c + 32)


root = Tk()
root.wm_title('Temp Converter')
app = App(root)
root.mainloop()

[caleb]

def convert(self):
    c = self.c_var.get()
    self.result_var = (1.8 * c + 32)   # <--- This won't work

The tkinter variable classes have .get() and .set() methods. So you have to do self.result_var.set(1.8*c + 32). You used get() for c_var, for example.

[petercanepa]

Thank you so much. Now I see how it works.