Where did you find that?
Quoted in full from the gift:
Subject: Re: Python CTypes translation of (pv != NULL)
Date: Tue, 26 Sep 2006 11:48:52 +0200
Message-ID: [EMAIL PROTECTED]
http://groups.google.com/group/comp.lang.python/msg/f9f13e731ea3cad7
Cached and pondered just slightly before
Future Googlers might like this thread to end with the Thomas Heller's
brief conclusive review:
/// Copied 2006-09-28 from
/// http://starship.python.net/crew/theller/moin.cgi/CodeSnippets
1.2 Check for NULL ctypes pointers
The truth value of any NULL ctypes pointer instance is False.
So, this
http://starship.python.net/crew/theller/ctypes/tutorial.html
...
direct discussion only of how to construct null pointers,
no discussion of how to test for them ...
...
could be read to mean try ... == ... is ... False ... None ...
CTypes nulls fetched from a struct feel more like None
It says:
NULL pointers have a False boolean value:
null_ptr = POINTER(c_int)()
print bool(null_ptr)
False
Yes.
That means that NULL pointers are considered False in a boolean
expression (and you could assume that non-NULL pointers are True, as
any other object in general),
I see
[EMAIL PROTECTED] schrieb:
It says:
NULL pointers have a False boolean value:
null_ptr = POINTER(c_int)()
print bool(null_ptr)
False
Yes.
That means that NULL pointers are considered False in a boolean
expression (and you could assume that non-NULL pointers are True, as
any other
At Wednesday 27/9/2006 13:40, [EMAIL PROTECTED] wrote:
That means that NULL pointers are considered False in a boolean
expression (and you could assume that non-NULL pointers are True, as
any other object in general),
I see this now that you show the clueless newbie me, yes thank you.
At Wednesday 27/9/2006 13:35, [EMAIL PROTECTED] wrote:
http://starship.python.net/crew/theller/ctypes/tutorial.html
...
direct discussion only of how to construct null pointers,
no discussion of how to test for them ...
...
could be read to mean try ... == ... is ... False ... None ...
At Monday 25/9/2006 21:27, [EMAIL PROTECTED] wrote:
Q: The C idea of (pv != NULL) is said most directly in Python ctypes
how?
Perhaps reading the ctypes tutorial? (both in the 2.5 docs and in
http://starship.python.net/crew/theller/ctypes/tutorial.html)
Gabriel Genellina
Softlab SRL
[EMAIL PROTECTED] schrieb:
Q: The C idea of (pv != NULL) is said most directly in Python ctypes
how?
A: We are of course supposed to write something like:
def c_not_null(pv):
return (ctypes.cast(pv, ctypes.c_void_p).value != None)
Yes?
Working from the doc,
Q: The C idea of (pv != NULL) is said most directly in Python ctypes
how?
Perhaps reading the ctypes tutorial? (both in the 2.5 docs and in
http://starship.python.net/crew/theller/ctypes/tutorial.html)
Actually, no. I see three answers or zero, depending on how you like
to count.
Yes that
Q: The C idea of (pv != NULL) ...
CTypes tutorial ... == False ... == None ... is None ...
Generally ... 'if pv: ' ... should work.
Except for c_void_p, c_char_p and c_wchar_p instances.
Please can we give me an example of these exceptions?
Indeed those types are the _p types I
At Tuesday 26/9/2006 16:00, [EMAIL PROTECTED] wrote:
Q: The C idea of (pv != NULL) is said most directly in Python ctypes
how?
Perhaps reading the ctypes tutorial? (both in the 2.5 docs and in
http://starship.python.net/crew/theller/ctypes/tutorial.html)
Actually, no. I see three answers
Q: The C idea of (pv != NULL) is said most directly in Python ctypes
how?
A: We are of course supposed to write something like:
def c_not_null(pv):
return (ctypes.cast(pv, ctypes.c_void_p).value != None)
Yes?
Working from the doc, me the clueless newbie, I was slow to
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