On Mac OS 10.12.4, a large shelve, backed by ndbm, can be created. But when I attempt to iterate through the values of the shelve it raises this exception:


  File "/Library/Frameworks/Python.framework/Versions/3.5/lib/python3.5/site-packages/dedupe/api.py", line 281, in _blockData
    for block in viewvalues(blocks):
  File "/Library/Frameworks/Python.framework/Versions/3.5/lib/python3.5/_collections_abc.py", line 693, in __iter__
    for key in self._mapping:
  File "/Library/Frameworks/Python.framework/Versions/3.5/lib/python3.5/shelve.py", line 95, in __iter__
    for k in self.dict.keys():
SystemError: Negative size passed to PyBytes_FromStringAndSize

I've confirmed that this works with Python 3.6.1. All the Python versions were installed from homebrew.

I cannot reproduce on linux on windows machines. I've attached a zip file of the ndbm files that python created.