BTreesAPI

BTrees, Buckets

• All mapping types implement a dictionary-like API. That means all known dictionary methods work on BTrees? instances:
  • keys() -- return a sequence containing the keys
  • values() -- return a sequence containing the values
  • items() -- return a sequence of tuples (key,value) ordered by key
  • __getitem__(key) -- return the value for key
  • __setitem__(key,value) -- set the value for a given key
  • __delitem__(key) -- remove the key
  • __len__() -- returns the number of elements in the BTree
  • has_key(key) - return 1 if key exists, otherwise 0
  • get(key, default) - return the value for key or the default value
  • update(mapping) - insert every (key, value) pair into the BTree
  • insert(key,value) - insert a (key, value) into the BTree.

    The BTree is not changed when key is already in the BTree. In this case insert() returns 0. Otherwise (key,value) is inserted and insert() returns 1.

    Remark: only available for BTree objects and not for Bucket objects

• Additional API unique to BTrees?:
  • byValue() -- like items(), returns a sequence of tuples, but returns (value, key) instead of (key, value) in the returned list, and ordered by value.

Sets, TreeSets

• The BTrees? set datatypes act as a mutable sequence (similiar to lists) but with the following differences compared to Python sequences:
  • all elements of a set are unique
  • elements are sorted

  Sets implement the following functions:

  • __len__() -- returns the number of items in set
  • insert(item) -- inserts a new item
  • remove(item) -- removes an item
  • index(item) -- returns the position of item in set
  • update(sequence) -- inserts every item in sequence to the set
  • __getitem__(index): -- return the key in the given index position

    Used for iteration

    Remark: only available for Set objects and not for TreeSet objects

• Additional API unique to BTrees?:
  • minKey(min=None) -- return the minimal item from the set. If min is present, then the smallest key that is greater than or equal to min is returned
  • maxKey(max=None) -- return the maximum item from the set. If max is present then the largest key that is smaller than or equal to max is returned.
  • keys(min,max) -- peforms a range search and returns a list of items that a larger min and smaller than max.

Sets do not have index() method in ZODB 3.3 --[stevea]?, 2004/02/12 13:22 EST reply
Note that Sets do not have an index() method in ZODB 4 and ZODB 3.3. That method doesn't make sense for sets anyway.