In IDLE the following code silently works:
>>> del __builtins__
>>> min
<built-in function min>

In the standard interpreter, it produces an error:
>>> del __builtins__
>>> min
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
NameError: name 'min' is not defined

Note that saying `__builtins__ = 7` fails in idle as well.