[Tutor] perplexing error with shelve REVISED

[Orest Kozyar]

> Please post the entire traceback (omitting duplicate lines). 

Sorry, I should have included the traceback.  I've revised the sample script
so that it generates the traceback when run.  The sample script is at the
very bottom of this email.

####### SCRIPT OUTPUT #######
[kozyar]:~$ python example.py 

Successfully retrieved and parsed XML document with ID 16842423
Successfully shelved XML document with ID 16842423
Successfully retrieved and parsed XML document with ID 16842422

Traceback (most recent call last):
  File "example.py", line 30, in <module>
    data[badkey] = doc
  File "/usr/lib64/python2.5/shelve.py", line 123, in __setitem__
    p.dump(value)
RuntimeError: maximum recursion depth exceeded

Exception exceptions.RuntimeError: 'maximum recursion depth exceeded' in
<bound method DbfilenameShelf.__del__ of {'16842423':
<xml.dom.minidom.Document instance at 0x96f290>}> ignored


####### START SCRIPT #######
import urllib, shelve
from xml.dom import minidom

baseurl = 'http://eutils.ncbi.nlm.nih.gov/entrez/eutils/efetch.fcgi?'

params = {
        'db':       'pubmed',
        'retmode':  'xml',
        'rettype':  'medline'
        }

badkey = '16842422'
goodkey = '16842423' #or just about any other ID

data = shelve.open('data.tmp', writeback=True)

params['id'] = goodkey
url = baseurl + urllib.urlencode(params)
doc = minidom.parseString(urllib.urlopen(url).read())
print 'Successfully retrieved and parsed XML document with ID %s' % goodkey
data[goodkey] = doc
print 'Successfully shelved XML document with ID %s' % goodkey

params['id'] = badkey
url = baseurl + urllib.urlencode(params)
doc = minidom.parseString(urllib.urlopen(url).read())
print 'Successfully retrieved and parsed XML document with ID %s' % badkey
data[badkey] = doc
#Will fail on the above line
print 'Successfully shelved XML document with ID %s' % badkey