Re: semi-newbie module namespace confusion
[EMAIL PROTECTED] wrote:
The main jist of the problem is that I'm trying add data from one
module to a list and a dictionary in another module, and it doesn't
seem to stick over there.
It's probably best to avoid any circular depentencies, but as
long as you make sure you really use your modules as modules,
and not one of them aas a main prorgam, I think it should work.
$ cat a.py
import b
def set_b(n):
b.b=n
$ cat b.py
import a
def set_a(n):
a.a=n
$ python
Python 2.2.3 (#1, Feb 2 2005, 12:20:51)
[GCC 3.2.3 20030502 (Red Hat Linux 3.2.3-49)] on linux2
Type help, copyright, credits or license for more information.
import a,b
a.set_b('B')
b.set_a('A')
a.a
'A'
b.b
'B'
--
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Re: semi-newbie module namespace confusion
[EMAIL PROTECTED] wrote: The main jist of the problem is that I'm trying add data from one module to a list and a dictionary in another module, and it doesn't seem to stick over there. The programs below seem to illustrate the issue. (The results follow the programs). Why are the results different from runs of the two programs? The output of nameSpaceTestB.py makes sense to me, but I just don't get why nameSpaceTestA.py does what it does. I'm sure the reason is very simple, but I just don't see it. Please, can someone shed some light on the issue for me? running a piece of python code as a script isn't the same thing as importing it as a module: If you run a module as a script (i.e. give its name to the inter- preter, rather than importing it), it's loaded under the module name __main__. If you then import the same module from your program, it's re- loaded and reexecuted under its real name. If you're not careful, you may end up doing things twice. http://effbot.org/zone/import-confusion.htm try changing your printing from-statements to print printing from, __name__ to see what you're really doing. /F -- http://mail.python.org/mailman/listinfo/python-list
Re: semi-newbie module namespace confusion
Fredrik Lundh wrote: running a piece of python code as a script isn't the same thing as importing it as a module: I ran into the same problem some time ago and even wanted to post here about it, but found out that it had been reported as a bug three times at sourceforge (if i remember correctly). The comments there explained it of course, but I still think that this behavior is somehow wrong. I like to think of the import statement as a way to provide the names defined in a module to the current namespace, so there is no this gets evaluated twice. Now i wonder how difficult it would be to correct the behavior? And would such a change break any code? David. -- http://mail.python.org/mailman/listinfo/python-list
Re: semi-newbie module namespace confusion
David Murmann wrote: I ran into the same problem some time ago and even wanted to post here about it, but found out that it had been reported as a bug three times at sourceforge (if i remember correctly). The comments there explained it of course, but I still think that this behavior is somehow wrong. I like to think of the import statement as a way to provide the names defined in a module to the current namespace, so there is no this gets evaluated twice. are you sure you understand the problem? import does exactly what you say; it creates a module object and populates it by running the code in the module. the problem is that when you hand Python a chunk of code (a script), it doesn't necessarily know where it came from. and even if you know the filename it came from, there's no way to know if that chunk actually corre- sponds to a module somewhere out there (the import system can map a module name to a file, but it cannot map a file to a module name). Now i wonder how difficult it would be to correct the behavior? there's no way to fix it without introducing a huge number of inconsistencies. And would such a change break any code? any code that uses the if __name__ == __main__ pydiom, for a start. /F -- http://mail.python.org/mailman/listinfo/python-list
Re: semi-newbie module namespace confusion
Fredrik Lundh wrote: David Murmann wrote: I ran into the same problem some time ago and even wanted to post here about it, but found out that it had been reported as a bug three times at sourceforge (if i remember correctly). The comments there explained it of course, but I still think that this behavior is somehow wrong. I like to think of the import statement as a way to provide the names defined in a module to the current namespace, so there is no this gets evaluated twice. are you sure you understand the problem? import does exactly what you say; it creates a module object and populates it by running the code in the module. maybe i don't... but i'm not convinced yet, see below. the problem is that when you hand Python a chunk of code (a script), it doesn't necessarily know where it came from. and even if you know the filename it came from, there's no way to know if that chunk actually corre- sponds to a module somewhere out there (the import system can map a module name to a file, but it cannot map a file to a module name). well, in my opinion python is not trying hard enough. to me it is immediately obvious that the main module gets evaluated twice and i am rather sure that one could introduce some magic of the kind oh, i reevaluate the main script here, the module does not get filled the usual way but uses the existing objects instead. this would have to happen on a very low level (when the file i just read from is known) but i think it would be possible. whether the effort to do so is worth it, is a different question... Now i wonder how difficult it would be to correct the behavior? there's no way to fix it without introducing a huge number of inconsistencies. And would such a change break any code? any code that uses the if __name__ == __main__ pydiom, for a start. i wouldn't lose that, the main module should still be named __main__, it should just get more names (somehow) :) i see, it's difficult at the moment hoping i'm not completely wrong here, David. -- http://mail.python.org/mailman/listinfo/python-list
Re: semi-newbie module namespace confusion
well, in my opinion python is not trying hard enough. to me it isimmediately obvious that the main module gets evaluated twice andi am rather sure that one could introduce some magic of the kind"oh, i reevaluate the main script here, the module does not get filledthe usual way but uses the existing objects instead". this would haveto happen on a very low level (when the file i just read from is known)but i think it would be possible. whether the effort to do so is worthit, is a different question...There is an easy fix to this situation, and it's called creating a new script that imports the modules. If it's truely a module (which I guess really everything in python is), it probably should only be run by itself for testing purposes only.Now i wonder how difficult it would be to "correct" the behavior? there's no way to "fix" it without introducing a huge number of inconsistencies.Plus, it's not broken to begin with. ---Andrew Gwozdziewycz[EMAIL PROTECTED]http://ihadagreatview.orghttp://plasticandroid.org -- http://mail.python.org/mailman/listinfo/python-list
Re: semi-newbie module namespace confusion
I'm not going to quote anything (except a URI), but thanks very much for your help, especially http://effbot.org/zone/import-confusion.htm. Almost certainly the source (and solution) to my problem lies in what you guys have brought out. I'm no longer stuck (at least I hope not), and I have knowledge to use in working out the solution. Kind Regards, ~Peter -- http://mail.python.org/mailman/listinfo/python-list
semi-newbie module namespace confusion
I've stuck my neck out and am in the integration stage of a rather important project at my company, which wears dot net blinders. The program is not too big: I've cranked out 3K lines of code, quite a bit of which is unit tested, but my eyes are starting to glaze, and now I'm stuck (and not just my neck :-). If I can get the show back on the road and bring it to a conclusion, I'll be able to persuade a lot of people to look closely at Python (not to mention the job retention aspect :-). The main jist of the problem is that I'm trying add data from one module to a list and a dictionary in another module, and it doesn't seem to stick over there. The programs below seem to illustrate the issue. (The results follow the programs). Why are the results different from runs of the two programs? The output of nameSpaceTestB.py makes sense to me, but I just don't get why nameSpaceTestA.py does what it does. I'm sure the reason is very simple, but I just don't see it. Please, can someone shed some light on the issue for me? Thanks! ~Peter - nameSpaceTestA.py: import nameSpaceTestB as NSB normalQ = [ 37] abc = 25 def indirect( ) : normalQ.append( 44) print printing from NSA: print normalQ NSB.updateNSA( ) print printing from NSA: print normalQ print abc = %d % abc if __name__ == '__main__' : indirect() - nameSpaceTestB.py: import nameSpaceTestA as NSA def updateNSA( ) : print printing from NSB: print NSA.normalQ NSA.normalQ.append( gotcha) print NSA.normalQ print NSA.abc NSA.abc = 666 print NSA.abc if __name__ == '__main__' : NSA.indirect() - py24 nameSpaceTestA.py printing from NSA: [37, 44] printing from NSB: [37] [37, 'gotcha'] 25 666 printing from NSA: [37, 44] abc = 25 - py24 nameSpaceTestB.py printing from NSA: [37, 44] printing from NSB: [37, 44] [37, 44, 'gotcha'] 25 666 printing from NSA: [37, 44, 'gotcha'] abc = 666 -- http://mail.python.org/mailman/listinfo/python-list
