[2.2] Weird behaviour of file.write() (no data written)?

[Mike C. Fletcher]

I'm trying to figure out what's going wrong with my index-storing 
routines.  These are dirt-simple pickle-dumps to disk.  I must be doing 
something terribly obviously wrong, but darned if I can figure out what 
it is.


Here's the relevant code:

fileHandle = open( self.filename,'wb',0)
values = {}
for key, value in self.tables.items():
	if isinstance( key, Persistent ):
		if not hasattr( key, '_p_oid'):
			raise ValueError( """Attempting to store a collection index for a 
collection not currently in the database %s"""%( key))
		key = key._p_oid
	values[key] = value
self.tables = values
print 'dumping indices to', self.filename
data = dumps( values)
fileHandle.write( data)
fileHandle.write( '')
fileHandle.flush()
fileHandle.close()
print 'fileHandle closed'


What happens with that code is that a 0-length file is created on disk, 
despite the pickle being 7 or 8 kb in length.  Now, this code works (no 
clue why it's even different):

values = {}
for key, value in self.tables.items():
	if isinstance( key, Persistent ):
		if not hasattr( key, '_p_oid'):
			raise ValueError( """Attempting to store a collection index for a 
collection not currently in the database %s"""%( key))
		key = key._p_oid
	values[key] = value
self.tables = values
print 'dumping indices to', self.filename
data = dumps( values)
fileHandle = open( self.filename,'wb',0)
fileHandle.write( data)
fileHandle.write( '')
fileHandle.flush()
fileHandle.close()
print 'fileHandle closed'

(The only difference being _when_ the fileHandle object is created). 
I've tried buffered and unbuffered files, using pickle.dump instead of 
dumps, and just about everything else I could think of.

The code is getting called in the OnClose handler of a wxPython wxFrame 
object.  Zope 3's ZODB is being used (it's what's pulling in 
Persistent), but I'm not using it for the indices (the only things in 
the indices are readily pickle-able objects).


There's lots of alpha or beta-quality C software running around this 
application (Zope3 and wxPython 2.3.3pre2, respectively), but I'd be 
surprised if it could affect something as stable as file.write without 
causing something a little more obvious to occur.

Ideas welcome,
Mike
_______________________________________
   Mike C. Fletcher
   http://members.rogers.com/mcfletch/