BTrees: scalable persistent components

This package contains a set of persistent object containers built around a modified BTree data structure. The trees are optimized for use inside ZODB's "optimistic concurrency" paradigm, and include explicit resolution of conflicts detected by that mechanism.

Please see the Sphinx documentation for further information.

BTrees Changelog

6.1 (2024-09-17)

• Add final support for Python 3.13.

6.0 (2024-05-30)

• Drop support for Python 3.7.
• Build Windows wheels on GHA.

5.2 (2024-02-07)

• Add preliminary support for Python 3.13 as of 3.13a3.

5.1 (2023-10-05)

• Drop using setup_requires due to constant problems on GHA.
• Add support for Python 3.12.

5.0 (2023-02-10)

• Build Linux binary wheels for Python 3.11.
• Drop support for Python 2.7, 3.5, 3.6.

4.11.3 (2022-11-17)

• point release to rebuild full set of wheels

4.11.2 (2022-11-16)

• Add support for building arm64 wheels on macOS.

4.11.1 (2022-11-09)

• Fix macOS wheel build issues on GitHub Actions
• We no longer provide 32bit wheels for the Windows platform, only x86_64.

4.11.0 (2022-11-03)

• Add support for Python 3.11.

4.10.1 (2022-09-12)

• Disable unsafe math optimizations in C code. (#184)

4.10.0 (2022-03-09)

• Add support for Python 3.10.

4.9.2 (2021-06-09)

• Fix fsBTree.TreeSet and fsBTree.BTree raising SystemError. See issue 170.
• Fix all the fsBTree objects to provide the correct interfaces and be instances of the appropriate collection ABCs. This was done for the other modules in release 4.8.0.
• Fix the multiunion, union, intersection, and difference functions when used with arbitrary iterables. Previously, the iterable had to be pre-sorted, meaning only sequences like list and tuple could reliably be used; this was not documented though. If the iterable wasn't sorted, the function would produce garbage output. Now, if the function detects an arbitrary iterable, it automatically sorts a copy.

4.9.1 (2021-05-27)

• Fix setting unknown class attributes on subclasses of BTrees when using the C extension. This prevented subclasses from being decorated with @component.adapter(). See issue 168.

4.9.0 (2021-05-26)

• Fix the C implementation to match the Python implementation and allow setting custom node sizes for an entire application directly by changing BTree.max_leaf_size and BTree.max_internal_size attributes, without having to create a new subclass. These attributes can now also be read from the classes in the C implementation. See issue 166.
• Add various small performance improvements for storing zope.interface attributes on BTree and TreeSet as well as deactivating persistent objects from this package.

4.8.0 (2021-04-14)

• Make Python 2 forbid the use of type objects as keys (unless a custom metaclass is used that implements comparison as required by BTrees.) On Python 3, types are not orderable so they were already forbidden, but on Python 2 types can be ordered by memory address, which makes them unsuitable for use as keys. See issue.
• Make the multiunion, union, intersection, and difference functions accept arbitrary Python iterables (that iterate across the correct types). Previously, the Python implementation allowed this, but the C implementation only allowed objects (like TreeSet or Bucket) defined in the same module providing the function. See issue 24.
• Fix persistency bug in the Python version (#118).
• Fix Tree.__setstate__ to no longer accept children besides tree or bucket types to prevent crashes. See PR 143 for details.
• Make BTrees, TreeSet, Set and Buckets implements the __and__, __or__ and __sub__ special methods as shortcuts for BTrees.Interfaces.IMerge.intersection, BTrees.Interfaces.IMerge.union and BTrees.Interfaces.IMerge.difference.
• Add support for Python 3.9.
• Build and upload aarch64 wheels.
• Make a value of 0 in the PURE_PYTHON environment variable require the C extensions (except on PyPy). Previously, and if this variable is unset, missing or unusable C extensions would be silently ignored. With this variable set to 0, an ImportError will be raised if the C extensions are unavailable. See issue 156.
• Make the BTree objects (BTree, TreeSet, Set, Bucket) of each module actually provide the interfaces defined in BTrees.Interfaces. Previously, they provided no interfaces.
• Make all the BTree and Bucket objects instances of collections.abc.MutableMapping (that is, isinstance(btree, MutableMapping) is now true; no actual inheritance has changed). As part of this, they now provide the popitem() method.
• Make all the TreeSet and Set objects instances of collections.abc.MutableSet (that is, isinstance(tree_set, MutableSet) is now true; no actual inheritance has changed). As part of this, they now provide several more methods, including isdisjoint, discard, and pop, and support in-place mutation operators such as tree_set |= other, tree_set += other, tree_set -= other and tree_set ^= other. See issue 121.
• Update the definitions of ISized and IReadSequence to simply be zope.interface.common.collections.ISized and zope.interface.common.sequence.IMinimalSequence respectively.
• Remove the __nonzero__ interface method from ICollection. No objects actually implemented such a method; instead, the boolean value is typically taken from __len__.
• Adjust the definition of ISet to produce the same resolution order under the C3 and legacy orderings. This means that the legacy order has changed slightly, but that this package emits no warnings when ZOPE_INTERFACE_LOG_CHANGED_IRO=1. Note that the legacy order was not being used for these objects because the C3 ordering was still consistent; it could only be obtained using ZOPE_INTERFACE_USE_LEGACY_IRO=1. See PR 159 for all the interface updates.
• Fix the get, setdefault and pop methods, as well as the in operator, to not suppress POSKeyError if the object or subobjects are corrupted. Previously, such errors were logged by ZODB, but not propagated. See issue 161.

4.7.2 (2020-04-07)

• Fix more cases of C and Python inconsistency. The C implementation now behaves like the Python implementation when it comes to integer overflow for the integer keys for in, get and has_key. Now they return False, the default value, and False, respectively in both versions if the tested value would overflow or underflow. Previously, the C implementation would raise OverflowError or KeyError, while the Python implementation functioned as expected. See issue 140.

  Note

  The unspecified true return values of has_key have changed.

4.7.1 (2020-03-22)

• Fix the definitions of __all__ in modules. In 4.7.0, they incorrectly left out names. See PR 132.
• Ensure the interface resolution order of all objects is consistent. See issue 137.

4.7.0 (2020-03-17)

• Add unsigned variants of the trees. These use the initial "U" for 32-bit data and "Q" for 64-bit data (for "quad", which is similar to what the C printf function uses and the Python struct module uses).
• Fix the value for BTrees.OIBTree.using64bits when using the pure Python implementation (PyPy and when PURE_PYTHON is in the environment).
• Make the errors that are raised when values are out of range more consistent between Python 2 and Python 3 and between 32-bit and 64-bit variants.
• Make the Bucket types consistent with the BTree types as updated in versions 4.3.2: Querying for keys with default comparisons or that are not integers no longer raises TypeError.

4.6.1 (2019-11-07)

• Add support for Python 3.8.

4.6.0 (2019-07-30)

• Drop support for Python 3.4.
• Fix tests against persistent 4.4.
• Stop accidentally installing the 'terryfy' package in macOS wheels. See issue 98.
• Fix segmentation fault in bucket_repr(). See issue 106.

4.5.1 (2018-08-09)

• Produce binary wheels for Python 3.7.
• Use pyproject.toml to specify build dependencies. This requires pip 18 or later to build from source.

4.5.0 (2018-04-23)

• Add support for Python 3.6 and 3.7.

• Drop support for Python 3.3.

• Raise an ImportError consistently on Python 3 if the C extension for BTrees is used but the persistent C extension is not available. Previously this could result in an odd AttributeError. See

• Fix the possibility of a rare crash in the C extension when deallocating items. See

• Respect the PURE_PYTHON environment variable at runtime even if the C extensions are available. See

• Always attempt to build the C extensions, but make their success optional.

• Fix a DeprecationWarning that could come from I and L objects in Python 2 in pure-Python mode. See

4.4.1 (2017-01-24)

Fixed a packaging bug that caused extra files to be included (some of which caused problems in some platforms).

4.4.0 (2017-01-11)

• Allow None as a special key (sorted smaller than all others).

  This is a bit of a return to BTrees 3 behavior in that Nones are allowed as keys again. Other objects with default ordering are still not allowed as keys.

4.3.2 (2017-01-05)

• Make the CPython implementation consistent with the pure-Python implementation and only check object keys for default comparison when setting keys. In Python 2 this makes it possible to remove keys that were added using a less restrictive version of BTrees. (In Python 3 keys that are unorderable still cannot be removed.) Likewise, all versions can unpickle trees that already had such keys. See: and

• Make the Python implementation consistent with the CPython implementation and check object key identity before checking equality and performing comparisons. This can allow fixing trees that have keys that now have broken comparison functions. See

• Make the CPython implementation consistent with the pure-Python implementation and no longer raise TypeError for an object key (in object-keyed trees) with default comparison on __getitem__, get or in operations. Instead, the results will be a KeyError, the default value, and False, respectively. Previously, CPython raised a TypeError in those cases, while the Python implementation behaved as specified.

  Likewise, non-integer keys in integer-keyed trees will raise KeyError, return the default and return False, respectively, in both implementations. Previously, pure-Python raised a KeyError, returned the default, and raised a TypeError, while CPython raised TypeError in all three cases.

4.3.1 (2016-05-16)

• Packaging: fix password used to automate wheel creation on Travis.

4.3.0 (2016-05-10)

• Fix unexpected OverflowError when passing 64bit values to long keys / values on Win64. See:

• When testing PURE_PYTHON environments under tox, avoid poisoning the user's global wheel cache.

• Ensure that the pure-Python implementation, used on PyPy and when a C compiler isn't available for CPython, pickles identically to the C version. Unpickling will choose the best available implementation. This change prevents interoperability problems and database corruption if both implementations are in use. While it is no longer possible to pickle a Python implementation and have it unpickle to the Python implementation if the C implementation is available, existing Python pickles will still unpickle to the Python implementation (until pickled again). See:

• Avoid creating invalid objects when unpickling empty BTrees in a pure-Python environment.

• Drop support for Python 2.6 and 3.2.

4.2.0 (2015-11-13)

• Add support for Python 3.5.

4.1.4 (2015-06-02)

• Ensure that pure-Python Bucket and Set objects have a human readable __repr__ like the C versions.

4.1.3 (2015-05-19)

• Fix _p_changed when removing items from small pure-Python BTrees/TreeSets and when adding items to small pure-Python Sets. See:

4.1.2 (2015-04-07)

• Suppress testing 64-bit values in OLBTrees on 32 bit machines. See:

• Fix _p_changed when adding items to small pure-Python BTrees/TreeSets. See:

4.1.1 (2014-12-27)

• Accomodate long values in pure-Python OLBTrees.

4.1.0 (2014-12-26)

• Add support for PyPy and PyPy3.
• Add support for Python 3.4.
• BTree subclasses can define max_leaf_size or max_internal_size to control maximum sizes for Bucket/Set and BTree/TreeSet nodes.
• Detect integer overflow on 32-bit machines correctly under Python 3.
• Update pure-Python and C trees / sets to accept explicit None to indicate max / min value for minKey, maxKey. (PR #3)
• Update pure-Python trees / sets to accept explicit None to indicate open ranges for keys, values, items. (PR #3)

4.0.8 (2013-05-25)

• Fix value-based comparison for objects under Py3k: addresses invalid merges of [OLI]OBTrees/OBuckets.
• Ensure that pure-Python implementation of OOBTree.byValue matches semantics (reversed-sort) of C implementation.

4.0.7 (2013-05-22)

• Issue #2: compilation error on 32-bit mode of OS/X.
• Test PURE_PYTHON environment variable support: if set, the C extensions will not be built, imported, or tested.

4.0.6 (2013-05-14)

• Changed the ZODB extra to require only the real ZODB package, rather than the ZODB3 metapackage: depending on the version used, the metapackage could pull in stale versions of this package and persistent.
• Fixed Python version check in setup.py.

4.0.5 (2013-01-15)

• Fit the repr of bucket objects, which could contain garbage characters.

4.0.4 (2013-01-12)

• Emulate the (private) iterators used by the C extension modules from pure Python. This change is "cosmetic" only: it prevents the ZCML zope.app.security:permission.zcml from failing. The emulated classes are not functional, and should be considered implementation details.
• Accomodate buildout to the fact that we no longer bundle a copy of 'persistent.h'.
• Fix test failures on Windows: no longer rely on overflows from sys.maxint.

4.0.3 (2013-01-04)

• Added setup_requires==['persistent'].

4.0.2 (2013-01-03)

• Updated Trove classifiers.
• Added explicit support for Python 3.2, Python 3.3, and PyPy. Note that the C extensions are not (yet) available on PyPy.
• Python reference implementations now tested separately from the C verions on all platforms.
• 100% unit test coverage.

4.0.1 (2012-10-21)

• Provide local fallback for persistent C header inclusion if the persistent distribution isn't installed. This makes the winbot happy.

4.0.0 (2012-10-20)

Platform Changes

• Dropped support for Python < 2.6.
• Factored BTrees as a separate distribution.

Testing Changes

• All covered platforms tested under tox.
• Added support for continuous integration using tox and jenkins.
• Added setup.py dev alias (installs nose and coverage).
• Dropped dependency on zope.testing / zope.testrunner: tests now run with setup.py test.

Documentation Changes

• Added API reference, generated via Spinx' autodoc.
• Added Sphinx documentation based on ZODB Guide (snippets are exercised via 'tox').
• Added setup.py docs alias (installs Sphinx and repoze.sphinx.autointerface).