You have to get the StringVar's value by invoking the get
method:
conf.write(e1.get())
Below is a very simple script to demonstrate:
from Tkinter import StringVar, Tk
Tk()
s = StringVar()
s.set('word')
print s, type(s)
print s.get(), type(s.get())
Output in terminal:
PY_VAR0 <type 'instance'>
word <type 'str'>