On Wed, 06 Jul 2005 10:00:02 -0400, Jp Calderone wrote: > On Wed, 06 Jul 2005 09:45:56 -0400, Peter Hansen <[EMAIL PROTECTED]> wrote: >>Tom Anderson wrote: >>> How about just getting rid of del? Removal from collections could be >>> done with a method call, and i'm not convinced that deleting variables >>> is something we really need to be able to do (most other languages >>> manage without it). >> >>Arguing the case for del: how would I, in doing automated testing, >>ensure that I've returned everything to a "clean" starting point in all >>cases if I can't delete variables? Sometimes a global is the simplest >>way to do something... how do I delete a global if not with "del"? >> > > Unless you are actually relying on the global name not being defined, > "someGlobal = None" would seem to do just fine. > > Relying on the global name not being defined seems like an edge case.
Er, there is a lot of difference between a name not existing and it being set to None. $ cat mymodule1.py # define some temporary names a, b, c, d, e, f = 1, 2, 3, 4, 5, 6 # do some work result = a+b+c+d*e**f # delete the temp variables del a del b del c del d del e del f $ cat mymodule2.py # define some temporary names a, b, c, d, e, f = 1, 2, 3, 4, 5, 6 # do some work result = a+b+c+d*e**f # delete the temp variables a = None b = None c = None d = None e = None f = None Now import them into Python: py> import mymodule1, mymodule2 py> dir(mymodule1) ['__file__', '__name__', result] py> dir(mymodule2) ['__file__', '__name__', result, a, b, c, d, e, f] Or worse, do this: py> a = 1 py> from mymodule2 import * py> a + 1 Traceback (most recent call last): File "<stdin>", line 1, in ? TypeError: unsupported operand type(s) for +: 'NoneType' and 'int' It is bad enough that from module import * can over-write your variables with the modules' variables, but for it to do so with DELETED variables is unforgivable. -- Steven. -- http://mail.python.org/mailman/listinfo/python-list
