Encountering "TypeError: 'NoneType' object is not subscriptable" while saving an ontology (onto.save())

[arundhati-b]

This is happening after I try to save an ontology after removing some of its Object Properties. Not sure what the exact cause is and how to fix it.

TypeError                                 Traceback (most recent call last)
<ipython-input-20-a50699e0134c> in <module>
     39     filename = "raw/"+DATASET+"_"+split+".owl"
     40     print(onto, len(list(onto.properties())), list(onto.properties()))
---> 41     onto.save(file = filename, format = "rdfxml")

d:\Programs\Anaconda3\envs\pytorch\lib\site-packages\owlready2\namespace.py in save(self, file, format, **kargs)
   1004       if _LOG_LEVEL: print("* Owlready2 * Saving ontology %s to %s..." % (self.name, file), file = sys.stderr)
   1005       file = open(file, "wb")
-> 1006       self.graph.save(file, format, **kargs)
   1007       file.close()
   1008     else:

d:\Programs\Anaconda3\envs\pytorch\lib\site-packages\owlready2\driver.py in save(self, f, format, commit, **kargs)
    223   def save(self, f, format = "rdfxml", commit = False, **kargs):
    224     if commit: self.parent.commit()
--> 225     _save(f, format, self, **kargs)
    226 
    227 

d:\Programs\Anaconda3\envs\pytorch\lib\site-packages\owlready2\driver.py in _save(f, format, graph, filter)
    500 
    501       else:
--> 502         o = _unabbreviate(o)
    503         s_lines.append("""  <%s rdf:resource="%s"/>""" % (p, o))
    504 

d:\Programs\Anaconda3\envs\pytorch\lib\site-packages\owlready2\driver.py in _unabbreviate(storid)
    290     @lru_cache(None)
    291     def _unabbreviate(storid):
--> 292       r = graph._unabbreviate(storid).replace("&", "&amp;")
    293       if r.startswith(base_iri):
    294         if base_iri.endswith("/"): return r[len(base_iri) :]

d:\Programs\Anaconda3\envs\pytorch\lib\site-packages\owlready2\triplelite.py in _unabbreviate(self, storid)
    489 
    490   def _unabbreviate(self, storid):
--> 491     return self.execute("SELECT iri FROM resources WHERE storid=? LIMIT 1", (storid,)).fetchone()[0]
    492 
    493   def get_storid_dict(self):

[therhappy]

Up: I get the same problem.
The saving mechanism doesn't work for custom ontologies. Given the error I thought it was a matter of IRI, but I couldn't find any quick fix.

[therhappy]

OK, I have a fix actually.

First, make sure your IRI has a protocol, so for instance you'd init with:
onto = owlready2.get_ontology('http://local_ontology.owl')

Then allow it to be saved by bytes writing:

p = 'local.owl'
with open(p, 'wb') as f:
    onto.save(f)

Remember however that this here is an unofficial and unmaintained fork, the actual repo is here:
https://bitbucket.org/jibalamy/owlready2/src/master/
And official issue board here:
http://owlready.306.s1.nabble.com/