Python - execfile函数

Question

考虑我文件的内容＆＃34; sandbox.py＆＃34;：

execfile('sandbox.py')

当我运行它时，它会产生如下巨大的重复错误：

Traceback (most recent call last):

  File "sandbox.py", line 1, in <module>
    execfile('sandbox.py')
  File "sandbox.py", line 1, in <module>
    execfile('sandbox.py')
  File "sandbox.py", line 1, in <module>
    execfile('sandbox.py')
  File "sandbox.py", line 1, in <module>
    execfile('sandbox.py')
  File "sandbox.py", line 1, in <module>
    execfile('sandbox.py')
  File "sandbox.py", line 1, in <module>
    execfile('sandbox.py')
  File "sandbox.py", line 1, in <module>
    execfile('sandbox.py')
  File "sandbox.py", line 1, in <module>
    execfile('sandbox.py')
  File "sandbox.py", line 1, in <module>
    execfile('sandbox.py')
  File "sandbox.py", line 1, in <module>
    execfile('sandbox.py')
#(.... Same thing for about a 1000 more times...)
KeyError: 'unknown symbol table entry'

总之，有人可以解释刚刚发生了什么吗？为什么在使用execfile时没有其他错误与字典相关的错误？