-----Original Message-----
From: py************* *************** ****@python.org [mailto:python-
li************* ************@py thon.org] On Behalf Of Reedick, Andrew
Sent: Tuesday, July 15, 2008 4:13 PM
To: Victor Noagbodji; py*********@pyt hon.org
Subject: RE: 'if name is not None:' v. 'if name:'
If name:
Then either
a) name is an object, and that object does not have a 'false'
value, such as False, zero, or empty.
or
b) name is NULL/None. No object.
Change that to:
If not name:
Then either
a) name is an object, and that object does not have a 'false'
value, such as False, zero, or empty.
or
b) name is NULL/None. No object. 0  1090  This thread has been closed and replies have been disabled. Please start a new discussion. Similar topics | |
by: Stewart Midwinter |
last post by:
I'd like to do something like the following:
a = 1; b = 2; c = None
mylist =
for my in mylist:
if my is None:
print 'you have a problem with %s' % my #this line is problematic
>>> You have a problem with None
|
by: Victor Noagbodji |
last post by:
>>what's the difference between these two statement?
Well that's exactly why I'm asking. Since None returns False in if
statements. Why do people use if name is not None: instead of simply
writing if not name?
--
NOAGBODJI Paul Victor
|
by: Reedick, Andrew |
last post by:
a
If name is None:
Then name is NULL, nothing, nada, no object, no memory allocated, a
NULL pointer
If name is not None:
Then name is an object. It's a pointer to some kind of allocated
structure in memory. No idea if it contains a false or true value.
|
by: Jerry Hill |
last post by:
On Tue, Jul 15, 2008 at 4:13 PM, Reedick, Andrew <jr9445@att.comwrote:
This is just plain untrue. If 'name is None' evaluates to true, then
the variable 'name' is bound to the singleton value None. It has
nothing to do with allocated memory or null pointers. All it means is
that someplace along the line you did the equivalent of 'name = None'
in your code.
--
Jerry
|
by: Fredrik Lundh |
last post by:
Victor Noagbodji wrote:
Because they want to distinguish between None and other values that
evaluate to False, of course. As the page I linked to explains, there
are many objects that evaluate to false in a boolean context; None is
just one of them.
Or to spell it out: if you need to distinguish between None and other
false values, use an explicit test. If you don't need to distinguish
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