title: Temperature Converter Issue
body: <p>I am making a temperature converter for my first main project using a GUI, namely the Tkinter module. I do not have any problems with initializing the GUI. That works fine (to my knowledge). I need some assistance with making the IF statements to call each function related to the conversion. The problem I am having with that is I am not sure how to show equivalence between two items from two different lists. Here is my code (I know that I am missing some things. Obviously the if statements.)</p>
  
  <pre><code>from tkinter import *
  
  gui = Tk()
  gui.title(string='Temperature Converter')
  #create the GUI
  fromUnit = StringVar()
  #variable which holds the value of which unit is active in "units1"
  toUnit = StringVar()
  #variable which holds the value of which unit is active in "units2"
  initialTemp = StringVar()
  #the initial temperature entered in "enterTemp" entry
  initialTemp.set('0')
  #set the initial temperature to 0
  convertedTemp = StringVar()
  #used to display the converted temperature through "displayTemp" 
  convertedTemp.set('0')
  #set the converted temperature to 0
  
  units1 = ('Celsius', 'Fahrenheit', 'Kelvin') #the units used in the OptionMenu
  units2 = ('Celsius', 'Fahrenheit', 'Kelvin')
  
  fromUnit.set(units1[0]) #set the active element to the item in index[0] of units1
  toUnit.set(units2[0]) #set the active element to the item in index[0] of units2
  
  # celsius-celcius conversion
  def celsius_to_celsius():
      currentTemp = float(initialTemp.get())
      convertedTemp.set(currentTemp)
  
  # celsius-kelvin conversion
  def celsius_to_kelvin():
      currentTemp = float(initialTemp.get())
      currentTemp = (currentTemp + 273.15)
      convertedTemp.set(currentTemp)
  
  # celsius-fahrenheit conversion
  def celsius_to_fahrenheit():
      currentTemp = float(initialTemp.get())
      currentTemp = (currentTemp * (9/5))+32
      convertedTemp.set(currentTemp)
  
  #fahrenheit-fahrenheit conversion
  def fahrenheit_to_fahrenheit():
      currentTemp = float(initialTemp.get())
      convertedTemp.set(currentTemp)
  
  #fahrenheit-celsius conversion
  def fahrenheit_to_celsius():
      currentTemp = float(initialTemp.get())
      currentTemp = ((currentTemp - 32)*(5/9))
      convertedTemp.set(currentTemp)
  
  #fahrenheit-kelvin conversion
  def fahrenheit_to_kelvin():
      currentTemp = float(initialTemp.get())
      currentTemp = ((currentTemp - 32)*(5/9)+273.15)
      convertedTemp.set(currentTemp)
  
  #kelvin-kelvin conversion
  def kelvin_to_kelvin():
      currentTemp = float(initialTemp.get())
      convertedTemp.set(currentTemp)
  
  #kelvin-celsius conversion
  def kelvin_to_celsius():
      currentTemp = float(initialTemp.get())
      currentTemp = (currentTemp - 273.15)
      convertedTemp.set(currentTemp)
  
  #kelvin-fahrenheit conversion
  def kelvin_to_fahrenheit():
      currentTemp = float(initialTemp.get())
      currentTemp = (((currentTemp - 273.15)*(9/5))+32)
      convertedTemp.set(currentTemp)
  
  #main function
  #contains the if statements which select which conversion to use
  def convert_Temp():
      currentTemp = float(initialTemp.get())
      if (fromUnit, toUnit) == ('Celsius','Celsius'):
          celsius_to_celsius()
  
  
  gui.geometry('+100+100')
  #set up the geometry
  
  enterTemp = Entry(gui,textvariable=initialTemp,justify=RIGHT)
  enterTemp.grid(row=0,column=0)
  #Entry which receives the temperature to convert
  
  convertFromUnit = OptionMenu(gui,fromUnit,*units1)
  convertFromUnit.grid(row=0,column=1)
  #Option Menu which selects which unit to convert from
  
  displayTemp = Label(gui,textvariable=convertedTemp)
  displayTemp.grid(row=1,column=0)
  #Label which displays the temperature
  #Takes text variable "convertTemp"
  
  convertToUnit = OptionMenu(gui,toUnit,*units2)
  convertToUnit.grid(row=1,column=1)
  #Option Menu which selects which unit to convert to
  
  convertButton = Button(gui,text='Convert',command=convert_Temp)
  convertButton.grid(row=2,column=1)
  #Button that starts the conversion
  #Calls the main function "convert_Temp"
  
  gui.mainloop()
  #End of the main loop
  </code></pre>
  
  <p>Thanks for viewing and any help and criticism you provide. No knowledge is wasted!
  Cheers</p>