datetime.datetime object as key in BTree

[Kim Nikolay]

here example:

from datetime import datetime
from BTrees.OOBTree import OOBTree

tree = OOBTree()
tree[datetime.now()] = 'test1'
tree[datetime.now()] = 'test2'
tree.get(None, 'test3')

exceptions.TypeError

TypeError: can't compare datetime.datetime to NoneType
==================================================

but datetime.now() == None work

[Andreas Jung (ajung)]

Please include the *full* traceback

[Kim Nikolay (fafhrd)]

this happens when catalog objects with datetime attributes, but this is common problem in BTrees module

    * Module ZPublisher.Publish, line 115, in publish
    * Module ZPublisher.mapply, line 88, in mapply
    * Module ZPublisher.Publish, line 41, in call_object
    * Module Products.ZCatalog.ZCatalog, line 536, in manage_reindexIndex
    * Module Products.ZCatalog.ZCatalog, line 521, in reindexIndex
    * Module Products.CMFPlone.CatalogTool, line 329, in catalog_object
    * Module Products.ZCatalog.ZCatalog, line 565, in catalog_object
    * Module Products.ZCatalog.Catalog, line 360, in catalogObject
    * Module Products.PluginIndexes.common.UnIndex, line 243, in index_object
    * Module Products.PluginIndexes.common.UnIndex, line 270, in _index_object
    * Module Products.PluginIndexes.common.UnIndex, line 214, in insertForwardIndexEntry

TypeError: can't compare datetime.datetime to NoneType

[Andreas Jung (ajung)]

Status: Pending => Rejected

Keys in BTrees must be comparable. But None and datetime instances are not:

>>> cmp(datetime.datetime.now(), None)
Traceback (most recent call last):
  File "<stdin>", line 1, in ?
TypeError: can't compare datetime.datetime to NoneType

[Tim Peters (tim-one)]

As the Python datetime docs say, the datetime types support __eq__ and __ne__ comparisons, but not __le__, __lt__, __ge__ or __gt__. __eq__ and __ne__ are the only ones used by Python dictionaries, but BTrees require a total ordering and so require all 6 rich comparison operators. IOW, there's nothing to be done about this: you can't mix datetime and non-datetime types (including None) as keys in a BTree.