BMI Calculator [Python {wxPython}]

import wx
import time

class BMICalculator(wx.Frame):
    def __init__(self, parent, id):
        wx.Frame.__init__(self, parent, id, "BMI Calculator", (600, 800))
        self.panel = wx.Panel(self)
        self.panel.SetBackgroundColour("#FFFFFF")
        self.Centre()
        self.info_text = wx.StaticText(self.panel, -1, "Enter your height and weight and press compute to see your BMI.", (20, 15))
        self.label_text = wx.StaticText(self.panel, -1, "Body Mass Index: ", (20, 50))
        self.result_text = wx.StaticText(self.panel, -1, "... kg/(m*m)", (120, 50))
        self.error_label = wx.StaticText(self.panel, -1, "Error(s): ", (290, 50))
        self.error_text = wx.StaticText(self.panel, -1, "", (269, 65))
        self.static_text_height = wx.StaticText(self.panel, -1, "Height:", (20, 90))
        self.height = wx.SpinCtrlDouble(self.panel, -1, pos = (65, 87), size = (60, -1), min = 0, max = 300)
        self.static_text_height_extra = wx.StaticText(self.panel, -1, "(in centimeters)", (130, 90))
        self.static_text_weight = wx.StaticText(self.panel, -1, "Weight:", (20, 130))
        self.weight = wx.SpinCtrlDouble(self.panel, -1, pos = (65, 127), size = (60, -1), min = 0, max = 300)
        self.static_text_weight_extra = wx.StaticText(self.panel, -1, "(in kilograms)", (130, 130))
        self.bmi_underweight = wx.StaticText(self.panel, -1, "Underweight = < 18.5", (253, 90))
        self.bmi_normal_weight = wx.StaticText(self.panel, -1, "Normal weight = 18.5-24.9", (239, 110))
        self.bmi_overweight = wx.StaticText(self.panel, -1, "Overweight = 25-29.9", (254, 130))
        self.bmi_obesity = wx.StaticText(self.panel, -1, "Obesity = > 30", (274, 150))
        self.button_compute = wx.Button(self.panel, label = "Compute", pos = (40, 170), size = (60, -1))
        self.button_compute.SetBackgroundColour((0, 255, 0))
        self.button_compute.Bind(wx.EVT_BUTTON, self.onCompute)
        self.button_refresh = wx.Button(self.panel, label = "Refresh", pos = (122, 170), size = (60, -1))
        self.button_refresh.SetBackgroundColour((255, 165, 0))
        self.button_refresh.Bind(wx.EVT_BUTTON, self.onRefresh)
        self.button_theme = wx.Button(self.panel, label = "Theme", pos = (203, 170), size = (60, -1))
        self.button_theme.SetBackgroundColour((0, 255, 255))
        self.button_theme.Bind(wx.EVT_BUTTON, self.onThemeChange)
        self.button_cancel = wx.Button(self.panel, label = "Close", pos = (285, 170), size = (60, -1))
        self.button_cancel.SetBackgroundColour((255, 0, 0))
        self.button_cancel.Bind(wx.EVT_BUTTON, self.onClose)
        self.isBlack = False

    def onCompute(self, event):
        if (self.compute_BMI(self.height.GetValue(), self.weight.GetValue()) == None):
            self.result_text.SetLabel("... kg/(m*m)")
        else:
            self.result_text.SetLabel(str(self.compute_BMI(self.height.GetValue(), self.weight.GetValue())) + " kg/(m*m)")
        self.button_compute.SetBackgroundColour((0, 0, 255))
        time.sleep(0.1)
        self.button_compute.SetBackgroundColour((0, 255, 0))

    def onRefresh(self, event):
        self.result_text.SetLabel("... kg/(m*m)")
        self.error_text.SetLabel("")
        self.height.SetValue(0)
        self.weight.SetValue(0)

    def onThemeChange(self, event):
        if (self.isBlack == False):
            self.panel.SetBackgroundColour("Black")
            self.info_text.SetForegroundColour((255, 255, 255))
            self.label_text.SetForegroundColour((255, 255, 255))
            self.result_text.SetForegroundColour((255, 255, 255))
            self.error_label.SetForegroundColour((255, 255, 255))
            self.error_text.SetForegroundColour((255, 255, 255))
            self.static_text_height.SetForegroundColour((255, 255, 255))
            self.static_text_height_extra.SetForegroundColour((255, 255, 255))
            self.static_text_weight.SetForegroundColour((255, 255, 255))
            self.static_text_weight_extra.SetForegroundColour((255, 255, 255))
            self.bmi_underweight.SetForegroundColour((255, 255, 255))
            self.bmi_normal_weight.SetForegroundColour((255, 255, 255))
            self.bmi_overweight.SetForegroundColour((255, 255, 255))
            self.bmi_obesity.SetForegroundColour((255, 255, 255))
            self.button_compute.SetForegroundColour((255, 255, 255))
            self.button_refresh.SetForegroundColour((255, 255, 255))
            self.button_theme.SetForegroundColour((255, 255, 255))
            self.button_cancel.SetForegroundColour((255, 255, 255))
            self.isBlack = True
        elif (self.isBlack == True):
            self.panel.SetBackgroundColour("White")
            self.info_text.SetForegroundColour((0, 0, 0))
            self.label_text.SetForegroundColour((0, 0, 0))
            self.result_text.SetForegroundColour((0, 0, 0))
            self.error_label.SetForegroundColour((0, 0, 0))
            self.error_text.SetForegroundColour((0, 0, 0))
            self.static_text_height.SetForegroundColour((0, 0, 0))
            self.static_text_height_extra.SetForegroundColour((0, 0, 0))
            self.static_text_weight.SetForegroundColour((0, 0, 0))
            self.static_text_weight_extra.SetForegroundColour((0, 0, 0))
            self.bmi_underweight.SetForegroundColour((0, 0, 0))
            self.bmi_normal_weight.SetForegroundColour((0, 0, 0))
            self.bmi_overweight.SetForegroundColour((0, 0, 0))
            self.bmi_obesity.SetForegroundColour((0, 0, 0))
            self.button_compute.SetForegroundColour((0, 0, 0))
            self.button_refresh.SetForegroundColour((0, 0, 0))
            self.button_theme.SetForegroundColour((0, 0, 0))
            self.button_cancel.SetForegroundColour((0, 0, 0))
            self.isBlack = False
        self.panel.Refresh()

    def onClose(self, event):
        self.Close(True)
        self.button_cancel.SetBackgroundColour((0, 0, 255))
        time.sleep(0.1)
        self.button_cancel.SetBackgroundColour((255, 0, 0))

    def errorZeroDivision(self):
        self.error_text.SetLabel("Division by zero")

    def compute_BMI(self, height, weight):
        self.error_text.SetLabel("")
        height_m = float(height) / 100
        if ((height_m * height_m) == 0):
            self.errorZeroDivision()
            return None
        BMI = weight / (height_m * height_m)
        return BMI

def main():
    app = wx.App()
    frame = BMICalculator(None, -1)
    frame.Show()
    app.MainLoop()

if __name__ == "__main__":
    main()