title: Tkinter? Error converting string to integer?
body: <p>i'm new to tkinter. I'm trying to make a currency converter but when i try to convert the entry to a float(to convert to different currency ) i get this error.</p>
  
  <pre><code>Traceback (most recent call last):
  File "C:\Python33\lib\tkinter\__init__.py", line 1475, in __call__
  return self.func(*args)
  File "C:\Users\Nathan\Documents\New folder (3)\converter.py", line 40, in convert
  money = float( money.get() )
  ValueError: could not convert string to float: 
  </code></pre>
  
  <p>This is my code: 
      import tkinter
      from tkinter import *</p>
  
  <pre><code>root=tkinter.Tk()
  root.title('Currency Converter')
  root.minsize(300,300)
  root.geometry('500x500')
  
  
  def convert():
  nw= Toplevel()
  nw.title('Convert')
  nw.minsize(300,300)
  nw.geometry('400x400')
  am= Label(nw,text='Please enter the amount of money you have')
  money= Entry(nw, width=5)
  ra= Label(nw, text='Please enter the exchange rate')
  rate= Entry(nw,width=6)
  convert= Label(nw,text='You have')
  con= tkinter.Button(nw, text='Convert')
  b= tkinter.Button(nw, text= str(money))
  am.pack()
  money.pack()
  ra.pack()
  rate.pack()
  convert.pack()
  con.pack()
  b.pack()
  money = float( money.get() )
  
  
  
  welcome= Label(root,text='Welcome to Currency Converter, please select the conversion you wish to              use')
  pe= tkinter.Button(root, text='Pound - Euro', command=convert)
  ep= tkinter.Button(root, text='Euro - Pound', command=convert)
  
  welcome.pack()
  pe.pack()
  ep.pack()
  root.mainloop()
  </code></pre>