python程序运行期间出现的奇怪错误

Question

每当我运行程序时，我都会收到此错误。你知道这意味着什么吗？

时会发生这种情况

turtle.clear()

函数被称为

File "C:\Python32\lib\turtle.py", line 2642, in clear
    self._clear()
File "C:\Python32\lib\turtle.py", line 2621, in _clear
self.currentLineItem = self.screen._createline()
File "C:\Python32\lib\turtle.py", line 528, in _createline
capstyle = TK.ROUND)
File "C:\Python32\lib\tkinter\__init__.py", line 2185, in create_line
return self._create('line', args, kw)
File "C:\Python32\lib\tkinter\__init__.py", line 2173, in _create
*(args + self._options(cnf, kw))))
ValueError: invalid literal for int() with base 10: 'None'