title: NameError: name 's2gradefloat' is not defined
body: <p>I'm very new to python and i'm trying to create a GUI using tkinter that calculates the score you need on your final exam to get a certain grade. This is what I have so far:</p>
  
  <pre><code>from tkinter import *
  
  root = Tk()
  root.geometry("600x550+300+50")
  root.title("")
  backgroundcolor = '#%02x%02x%02x' %(0,0,0)
  root.config(background= backgroundcolor)
  #------------------Calculation----------------------#
  def crscore():
      s2grade = float(s2gradef.get())
      dgrade = float(dgradef.get())
      rscore = (100*dgrade - (100 - 50)* s2grade ) / 50
      rscorelabel=Label(root,text="Required Test Score: %s" %rscore).place(x=250,y=370)
      return
  #------------------Labels----------------------#
  Label1=Label(root,
  text='Final Exam Calclulator',
  fg='white',
  bg='black',
  font= "a 17 bold").place(x=170,y=20)
  Label3=Label(root,
  text='Enter Current Semester 2 Grade',
  fg='white',
  bg='black',
  font= "a 12 bold").place(x=100,y=100)
  
  Label4=Label(root,
  text='Enter Desired Final Grade',
  fg='white',
  bg='black',
  font= "a 12 bold").place(x=100,y=165)
  #------------------EntryBoxes----------------------#
  s2grade = StringVar()
  dgrade = StringVar()
  s2grade = Entry(root,textvariable=s2grade).place(x=395,y=100)
  dgrade = Entry(root,textvariable=dgrade).place(x=360,y=165)
  #------------------Button----------------------#
  button1=Button(root,text='Calculate Required Score',command=crscore).place(x=250,y=240)
  root.mainloop()
  </code></pre>
  
  <p>But keep getting the errors:</p>
  
  <pre><code>Traceback (most recent call last):
    File "C:\Python34\lib\tkinter\__init__.py", line 1538, in __call__
      return self.func(*args)
    File "E:/FinalProject.py", line 10, in crscore
      s2grade = float(s2gradefloat.get())
  NameError: name 's2gradefloat' is not defined
  </code></pre>
  
  <p>I realize i'm probably making many mistakes here. Can anyone help?</p>