On 01/10/2014 17:00, Steven D'Aprano wrote:
Out of curiosity, I ran:
globals().clear()
in the interactive interpreter. It broke much more than I expected!
Built-ins were no longer available, and import stopped working.
I expected that global variables would be all lost, but built-ins would
remain, since they don't live in the global namespace. I was wrong:
globals().clear()
x = len([])
Traceback (most recent call last):
File "<stdin>", line 1, in <module>
NameError: name 'len' is not defined
The reason, I think, is that CPython has a special __builtins__ global
variable that the interpreter uses to access built-in functions. What
*appears* to be happening is that if that __builtins__ global is missing,
CPython can not access the built-ins.
(Supporting this interpretation: IronPython, like CPython, has a
__builtins__ global, and behaves the same when the globals() are cleared.
Jython, which does not have a __builtins__ global, does not.)
Well that's okay, I thought to myself, I'll just import the built-in
functions:
from builtins import len # use '__builtin__' in Python 2
Traceback (most recent call last):
File "<stdin>", line 1, in <module>
ImportError: __import__ not found
Oops.
So, with no built-ins available, import no longer works. That makes things
rather tricky.
Obviously the easiest way to recover is to exit the current session and
restart it, but as a challenge, can we recover from this state?
We obviously need a Restart Command.
--
My fellow Pythonistas, ask not what our language can do for you, ask
what you can do for our language.
Mark Lawrence
--
https://mail.python.org/mailman/listinfo/python-list
