python tkinter中想打开一个.txt文件并显示在text中?报错

这是我写的open函数，但在打开文件时总会报错，望坛友赐教。

def open():

    fd = LoadFileDialog(root)
    filename = fd.go()
    file = open(""+filename,"r")
    te.setvar(file.read())
    file.close()
    print(filename)

error:Exception in Tkinter callback
Traceback (most recent call last):
  File "/usr/lib/python2.7/lib-tk/Tkinter.py", line 1489, in __call__
    return self.func(*args)
  File "/home/tom/PycharmProjects/farm/text.py", line 29, in open
    file = open(""+filename,"r")
TypeError: open() takes no arguments (2 given)