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PyPI · #4681 most downloaded on PyPI
A cython wrapping of the C++ Cap'n Proto library
Last release 3 months ago
03 Jul 2026
Release timing varies
gaps range from 8 days to 1.4 years
Nearly every release is documented
notes for 45 of 46 stable releases
Nothing withdrawn
no release was ever pulled
13 years old
50 releases · first in 2013
Fix memory leak in _DynamicCapabilityClient._send_helper()
_DynamicCapabilityClient._send_helper() (#398)uvpyproject.toml (removed Pipfile and requirements.txt)Fix test failures on Python 3.14
One column per quarter.
Revert Data fields to bytes and add get_data_as_view for zero-copy access
Make message.to_dict() return bytes for DATA type field
message.to_dict() return bytes for DATA type field (#386)Add binary support in dictionaries via base64 encoding
Remove usage of deprecated kj::mvCapture functions
Updated link for mailing list in README
Update README example to async code
reraise_kj_exception available to downstream_DynamicListReader in _setDynamicFieldUpdate to bundled capnproto-1.0.1
async (#312)async mode (#313)Update to bundled capnproto-0.10.3
Update bundled bundled capnp to 0.8.1 due to CVE-2022-46149
Fix packaging for Apple Silicon
Added support for Apple Silicon
Fix doc string for _DynamicResizableListBuilder
_DynamicResizableListBuilderValidated compatibility with Python 3.10.0b2
_StructModuleWhich to inherit from enum.Enum_SegmentArrayMessageReader__file__ is not set by importer_set_<field> for boolean fields*.c++ files_gen.py for python3 as dict_keys object are not indexable.pyproject.yaml_Schema for _StructSchemaValidated Python 3.9 (3.7 and 3.8 are also supported)
Minimum capnproto version is now 0.8.0
Python 3.7+ required (asyncio support)
Fix bugs in read_multiple_bytes (thanks to @tsh56)
read_multiple_bytes (thanks to @tsh56)Bump bundled capnp version to v0.6.1 (thanks to @E8Yuval)
Add support for buffers/memoryviews in from_bytes (thanks to @aldanor)
from_bytes (thanks to @aldanor)Fixed upload to PyPi (forgot to cythonize)
Bump bundled capnp version to v0.5.3.1
Make enums hashable (thanks to @madeleine-empirical)
from_bytes (thanks to @plesner)Fix bug that prevented event loop from actually being lazy initialized
clear_write_flag method to builder classesMake the event loop be lazy initialized
Fix build problem with Cython v0.24
result_type to InterfaceMethodSchemaUpdate bundled libcapnp to v0.5.2
bootstrap insteadinit method to listsFix a serious bug in TwoPartyServer that was preventing it from working when passed a string address.
Update bundled C++ libcapnp to v0.5.1.2 security release
Update bundled C++ libcapnp to v0.5.1.1 security release
Fix possible crash due to bad destructor ordering in MessageReader (by @JohnEmhoff)
Add read\_multiple\_bytes/read\_multiple\_bytes\_packed methods
Remove installation dependency on cython. We now have no dependencies since libcapnp will automatically build as well.
pycapnp is now thread-safe and allows an event loop to be run in each thread
capnp.getTimer()test_threads.py)from_bytes with builder=True is no longer zero copy. It never worked correctly, and is much safer nownum_first_segment_words argument wherever message creation can occurto_dictcapnp.types which completes all the Schemas needed to be wrapped. See test_schema.py for examples using itFix build for new 0.21 release of Cython. 0.21 is now the minimum supported version of Cython.
Fix to_dict not converting enums to strings
to_dict not converting enums to stringsFix compilation problem with gcc 4.8
Fix problem with uninitialized unions in \_from\_dict
Remove onDrained since it was removed upstream
_DynamicEnum class.Struct.which() method to be a property Struct.which and return an enum type (_DynamicEnumField, which behaves much like _DynamicEnum).__dir__)Remove python 3.2 from travis tests. Python 3.2 still should work fine, but it's more trouble than it's worth to write unicode tests that work in both
Add get_root_as_any to _MessageReader
Change naming of ReaderOption parameters to be pep8 compliant
Add defaults flag to capnp-json. Also remove 'which' field
as_builder method to Struct ReaderAdd not having installed the C++ libcapnp library to 'Common Problems'
- Fix problem with to_dict
Add _DynamicStructBuilder.to_bytes() and .from_bytes()
Change naming for functions to conform to PEP 8. Also deprecate old read/write API
Forgot to change project name in setup.py
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