Error:
TclError                                  Traceback (most recent call last)
<ipython-input-2-59f0c474d547> in <module>()
      3 import tkinter,qrcode,time
      4 import tkinter.messagebox
----> 5 window = tkinter.Tk()
      6 window.title('二维码生成器')
      7 window.geometry('500x200')

/usr/lib/python3.6/tkinter/__init__.py in __init__(self, screenName, baseName, className, useTk, sync, use)
   2021                 baseName = baseName + ext
   2022         interactive = 0
-> 2023         self.tk = _tkinter.create(screenName, baseName, className, interactive, wantobjects, useTk, sync, use)
   2024         if useTk:
   2025             self._loadtk()

TclError: no display name and no $DISPLAY environment variable