"Paul Rubin" <http://[EMAIL PROTECTED]> wrote in message news:[EMAIL PROTECTED]
> It's not obvious to me how the compiler can tell. Consider: > > x = 3 > if frob(): > frobbed = True > squares = [x*x for x in range(9)] > if blob(): > z = x > > Should the compiler issue a warning saying the program should be taken > out and shot? With lexical comprehensions, the program is perfectly > valid and sets z to 3 if blob() is true. The whole point of lexical > comprhensions is to make Python safe for such programs. > > Without lexical comprehensions, the program still doesn't depend on > the listcomp leakage if frob() and blob() aren't simultaneously true > (envision "assert not frobbed" before the "z = x"). So "should be > taken out and shot" is maybe a little bit extreme. Actually, I don't think so. If you intend for it to be impossible for "z = x" to refer to the x in the list comprehension, you shouldn't mind putting in "from __future__ import lexical_comprehensions." If you don't intend for it to be impossible, then the program *should* be taken out and shot. -- http://mail.python.org/mailman/listinfo/python-list
