Python – ttk tkinter multiple frames/windows


The following application I have created is used to demonstrate multiple windows in tkinter. The main problem is that none of the Entry controls, neither in the bmi-calculator or the converter, accept the values in the entry boxes – they get a ValueError when I do a calculation.

from tkinter import *
from tkinter import ttk
from tkinter import messagebox

class App1(ttk.Frame):
    def createWidgets(self):
        #text variables
        self.i_height = StringVar()
        self.i_weight = StringVar()
        self.o_bmi = StringVar()

        self.label1 = ttk.Label(self, text="Enter your weight:").grid(row=0, column=0, sticky=W)
        self.label2 = ttk.Label(self, text="Enter your height:").grid(row=1, column=0, sticky=W)
        self.label3 = ttk.Label(self, text="Your BMI is:").grid(row=2, column=0, sticky=W)

        #text boxes
        self.textbox1 = ttk.Entry(self, textvariable=self.i_weight).grid(row=0, column=1, sticky=E)
        self.textbox2 = ttk.Entry(self, textvariable=self.i_height).grid(row=1, column=1, sticky=E)
        self.textbox3 = ttk.Entry(self, textvariable=self.o_bmi).grid(row=2, column=1, sticky=E)

        self.button1 = ttk.Button(self, text="Cancel/Quit", command=self.quit).grid(row=3, column=1, sticky=E)
        self.button1 = ttk.Button(self, text="Ok", command=self.calculateBmi).grid(row=3, column=2, sticky=E)

    def calculateBmi(self):
            self.weight = float(self.i_weight.get())
            self.height = float(self.i_height.get())
            self.bmi = self.weight / self.height ** 2.0
        except ValueError:
            messagebox.showinfo("Error", "You can only use numbers.")

    def __init__(self, master=None):
        ttk.Frame.__init__(self, master)

class App2(ttk.Frame):
    def create_widgets(self):
        """Create the widgets for the GUI"""
        #1 textbox (stringvar)
        self.entry= StringVar()
        self.textBox1= ttk.Entry(self, textvariable=self.entry).grid(row=0, column=1)

        #5 labels (3 static, 1 stringvar)
        self.displayLabel1 = ttk.Label(self, text="feet").grid(row=0, column=2, sticky=W)
        self.displayLabel2 = ttk.Label(self, text="is equivalent to:").grid(row=1, column=0)
        self.result= StringVar()
        self.displayLabel3 = ttk.Label(self, textvariable=self.result).grid(row=1, column=1)
        self.displayLabel4 = ttk.Label(self, text="meters").grid(row=1, column=2, sticky=W)

        #2 buttons
        self.quitButton = ttk.Button(self, text="Quit", command=self.quit).grid(row=2, column=1, sticky=(S,E))
        self.calculateButton = ttk.Button(self, text="Calculate", command=self.convert_feet_to_meters).grid(row=2, column=2, sticky=(S,E))

    def convert_feet_to_meters(self):
        """Converts feet to meters, uses string vars and converts them to floats"""
        self.measurement = float(self.entry.get())
        self.meters = self.measurement * 0.3048

    def __init__(self, master=None):
        ttk.Frame.__init__(self, master)

def button1_click():
    root = Tk()
    app = App1(master=root)

def button2_click():
    root = Tk()
    app = App2(master=root)

def main():
    window = Tk()
    button1 = ttk.Button(window, text="bmi calc", command=button1_click).grid(row=0, column=1)
    button2 = ttk.Button(window, text="feet conv", command=button2_click).grid(row=1, column=1)

if __name__ == '__main__':

How can I fix this, but still maintaining the class structure and the use of python3? BTW – Anything similar to C#'s form1.Show()?

Best Solution

You have to convert the StringVar() to an integer/float or use IntVar() or DoubleVar()

There are other problems as well. Statements like the following return "None" since it is a grid() object and not a Label() object:

self.label1 = ttk.Label(self, text="Enter your weight:").grid(row=0, column=0, sticky=W)   

I think you will also have problems with two Tk() windows open at the same time. Use Toplevel() or separate frames instead.

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