GitLocker: The Coding Marketplace

Description:

pycapnp 2.0.0

pycapnp

Cap'n'proto Mailing List Documentation
Requirements

C++14 supported compiler

gcc 6.1+ (5+ may work)
clang 6 (3.4+ may work)
Visual Studio 2017+

cmake (needed for bundled capnproto)

ninja (macOS + Linux)
Visual Studio 2017+

capnproto-1.0 (>=0.8.0 will also work if linking to system libraries)

Not necessary if using bundled capnproto

Python development headers (i.e. Python.h)

Distributables from python.org include these, however they are usually in a separate package on Linux distributions

32-bit Linux requires that capnproto be compiled with -fPIC. This is usually set correctly unless you are compiling canproto yourself. This is also called -DCMAKE_POSITION_INDEPENDENT_CODE=1 for cmake.
pycapnp has additional development dependencies, including cython and pytest. See requirements.txt for them all.
Building and installation
Install with pip install pycapnp. You can set the CC environment variable to control which compiler is used, ie CC=gcc-8.2 pip install pycapnp.
Or you can clone the repo like so:
git clone https://github.com/capnproto/pycapnp.git
cd pycapnp
pip install .

By default, the setup script will automatically use the locally installed Cap'n Proto.
If Cap'n Proto is not installed, it will bundle and build the matching Cap'n Proto library.
To enforce bundling, the Cap'n Proto library:
pip install . -C force-bundled-libcapnp=True

If you wish to install using the latest upstream C++ Cap'n Proto:
pip install . \
-C force-bundled-libcapnp=True \
-C libcapnp-url="https://github.com/capnproto/capnproto/archive/master.tar.gz"

To enforce using the installed Cap'n Proto from the system:
pip install . -C force-system-libcapnp=True

The bundling system isn't that smart so it might be necessary to clean up the bundled build when changing versions:
python setup.py clean

Stub-file generation
While not directly supported by pycapnp, a tool has been created to help generate pycapnp stubfile to assist with development (this is very helpful if you're new to pypcapnp!). See #289 for more details.
Python Capnp Stub Generator
Python Versions
Python 3.8+ is supported.
Development
Git flow has been abandoned, use master.
To test, use a pipenv (or install requirements.txt and run pytest manually).
pip install pipenv
pipenv install
pipenv run pytest

Binary Packages
Building a Python wheel distributiion
pip wheel .

Documentation/Example
There is some basic documentation here.
Make sure to look at the examples. The examples are generally kept up to date with the recommended usage of the library.
The examples directory has one example that shows off pycapnp quite nicely. Here it is, reproduced:
import os
import capnp

import addressbook_capnp

def writeAddressBook(file):
addresses = addressbook_capnp.AddressBook.new_message()
people = addresses.init('people', 2)

alice = people[0]
alice.id = 123
alice.name = 'Alice'
alice.email = 'alice@example.com'
alicePhones = alice.init('phones', 1)
alicePhones[0].number = "555-1212"
alicePhones[0].type = 'mobile'
alice.employment.school = "MIT"

bob = people[1]
bob.id = 456
bob.name = 'Bob'
bob.email = 'bob@example.com'
bobPhones = bob.init('phones', 2)
bobPhones[0].number = "555-4567"
bobPhones[0].type = 'home'
bobPhones[1].number = "555-7654"
bobPhones[1].type = 'work'
bob.employment.unemployed = None

addresses.write(file)

def printAddressBook(file):
addresses = addressbook_capnp.AddressBook.read(file)

for person in addresses.people:
print(person.name, ':', person.email)
for phone in person.phones:
print(phone.type, ':', phone.number)

which = person.employment.which()
print(which)

if which == 'unemployed':
print('unemployed')
elif which == 'employer':
print('employer:', person.employment.employer)
elif which == 'school':
print('student at:', person.employment.school)
elif which == 'selfEmployed':
print('self employed')
print()

if __name__ == '__main__':
f = open('example', 'w')
writeAddressBook(f)

f = open('example', 'r')
printAddressBook(f)

Also, pycapnp has gained RPC features that include pipelining and a promise style API. Refer to the calculator example in the examples directory for a much better demonstration:
import asyncio
import capnp
import socket

import test_capability_capnp

class Server(test_capability_capnp.TestInterface.Server):

def __init__(self, val=1):
self.val = val

async def foo(self, i, j, **kwargs):
return str(i * 5 + self.val)

async def client(read_end):
client = capnp.TwoPartyClient(read_end)

cap = client.bootstrap()
cap = cap.cast_as(test_capability_capnp.TestInterface)

remote = cap.foo(i=5)
response = await remote

assert response.x == '125'

async def main():
client_end, server_end = socket.socketpair(socket.AF_UNIX)
# This is a toy example using socketpair.
# In real situations, you can use any socket.

client_end = await capnp.AsyncIoStream.create_connection(sock=client_end)
server_end = await capnp.AsyncIoStream.create_connection(sock=server_end)

_ = capnp.TwoPartyServer(server_end, bootstrap=Server(100))
await client(client_end)

if __name__ == '__main__':
asyncio.run(capnp.run(main()))

Changelog
v2.0.0 (2024-01-19)

Updated link for mailing list in README

v2.0.0b2 (2023-11-25)

Fix broken test in test_load (#329)
Update README example to async code (#331)
Fix 'AttributeError: '_UnixSelectorEventLoop' object has no attribute 'call_soon'
Delete and update some Python 3.7-specific todo notes
Make a server fail early when the KJ loop is not running
Update documentation to async code (#331) (#332)
Fix retransmit bug for large messages causing message corruption
Unlock the GIL for all capnp functions that do IO
Handle exceptions from server callbacks
Disable the use of ninja for windows builds
DynamicCapabilityClient fix
Make reraise_kj_exception available to downstream
Support _DynamicListReader in _setDynamicField
Fix re-raising of KjException
Allow cancellation of all capability contexts
Corner case for cancelled server methods that raise exceptions
Some fixes to the magic import system

v2.0.0b1 (2023-10-03)

Update to bundled capnproto-1.0.1
Remove support for Python 3.7
Use custom build backend to support build args (#328)
Update Cython version and Python to 3.12 (#320)
Wrap all capnp code in a context-manager to avoid segfaults (#317)
Schema loading from the wire (#307)
Make pycapnp more GIL friendly (#308)
Use cibuildwheel in ci (#309)
Integrate the KJ event loop into Python's asyncio event loop (#310)
Allow capability implementation methods to be async (#312)
Allow reading and writing messages from sockets in async mode (#313)
Remove the synchronous RPC mode (#315)

v1.3.0 (2023-01-26)

Update to bundled capnproto-0.10.3
Add Python 3.11 to Github Actions builds (#306)
Prevent race condition in example code (#305)

v1.2.2 (2022-12-01)

Update bundled bundled capnp to 0.8.1 due to CVE-2022-46149
Bundle lib/capnp_api.h and helpers/capabilityHelper.cpp (#301)
Avoid reading random values for reader options from dangling reference (#300)

v1.2.1 (2022-09-11)

Fix packaging for Apple Silicon

v1.2.0 (2022-08-29)

Added support for Apple Silicon

v1.1.1 (2022-05-23)

Added Python 3.10 support
aarch64 wheel support
Fix doc string for _DynamicResizableListBuilder
fix for unreleased buffers under mmap (issue 280)

v1.1.0 (2021-06-09)

Validated compatibility with Python 3.10.0b2
Remove all bare except
Improve _StructModuleWhich to inherit from enum.Enum
Add Union on top level union messages
Fixed memory leak in _SegmentArrayMessageReader
Removed many pycodestyle warnings
Avoid crash if __file__ is not set by importer
Fixed module.pyx _set_<field> for boolean fields
Fixed setup.py.tmpl support for *.c++ files
Fixed _gen.py for python3 as dict_keys object are not indexable.
Add test data to sdist
Add pyproject.yaml
Add missing inheritance to _Schema for _StructSchema

v1.0.0 (2020-11-20)

Validated Python 3.9 (3.7 and 3.8 are also supported)
Updated package to include LICENSE file
Updated examples to avoid run_forever() as ctrl+c will not work
Adding xfail to pytest cases which fail sometimes due to network port oddities (please use asyncio, as Python handles things more gracefully)

v1.0.0b2 (2020-06-14)

Minimum capnproto version is now 0.8.0
Added asyncio ssl calculator test
Added poll_once to TwoPartyServer API
More cleanup
Fix absolute and circular imports
Fix Promise aliasing issue (Promise to _Promise)
Documentation update
Updated installation instructions
Added RPC documentation for asyncio

v1.0.0b1 (2019-12-26)

Python 3.7+ required (asyncio support)
TLS/SSL support using asyncio
Windows support
General cleanup
May be incompatible with code written for pycapnp 0.6.4 and lower
Removing pypandoc/pandoc packaging requirement
Minimum capnproto version is now 0.7.0

v0.6.4 (2019-01-31)

Fix bugs in read_multiple_bytes (thanks to @tsh56)
Remove end-of-life Python versions 2.6, 3.2, and 3.3. Add CI tests for 3.6
Expose SchemaParser in Cython header

v0.6.3 (2018-01-14)

Bump bundled capnp version to v0.6.1 (thanks to @E8Yuval)
Fix a memleak in RemotePromise (thanks to @E8Yuval)

v0.6.2 (2017-11-30)

Add support for buffers/memoryviews in from_bytes (thanks to @aldanor)

v0.6.1 (2017-07-27)

Fixed upload to PyPi (forgot to cythonize)

v0.6.0 (2017-07-27)

Update bundled capnp version to v0.6.0 and fix related problems (thanks to @benmoran)
Fix memleak with KjException (thanks to @tsh56)

v0.5.12 (2017-04-18)

Bump bundled capnp version to v0.5.3.1

v0.5.11 (2017-04-10)

Make enums hashable (thanks to @madeleine-empirical)
Rework logic on when to build bundled libcapnp. Fixes cross-compilation (thanks to @benizl)
Add traversal_limit_in_words and nesting_limit to RPC classes (thanks to @asilversempirical)
Include class attributes in dir. This allows for code completion of class methods (thanks to @chaoflow )
Allow setting lists with python tuples (thanks to @chaoflow)
Fix traversal_limit_in_words and nesting_limit being ignored by from_bytes (thanks to @plesner)

v0.5.10 (2016-11-28)

Fix bug that prevented event loop from actually being lazy initialized
Fix possible recursive loop in KjException
Add clear_write_flag method to builder classes

v0.5.9 (2016-07-07)

Make the event loop be lazy initialized
Add support for segment (de)serialization (thanks to @gcv). See to_segments/from_segments methods.
Fix response objects not referencing parents correctly
Add test for large reads

v0.5.8 (2016-05-27)

Fix build problem with Cython v0.24
Include the changelog in the manifest (should fix install problems if pandoc is present)
Include the traceback in exceptions
Make sure to encode to utf-8, not the default encoding (thanks to @novas0x2a)
Add --libcapnp-url option in installer to allow installing arbitrary libcapnp versions
Support mmap objects for reading with from_bytes (thanks to @bpiwowar)
Change read_multiple and read_multiple_packed to copy by default
Fix mistakenly discarding the file parameter on reads
Add reraise_kj_exception to the prettyPrint functions. (thanks to @kdienes)
Fix KjException init (missing wrapper). (thanks to @E8-Storage)
Add result_type to InterfaceMethodSchema

v0.5.7 (2015-06-16)

Update bundled libcapnp to v0.5.2
Add warnings for using old restorer methods. You should use bootstrap instead
Fix warning from PyEventPort
Handle AnyPointers better as arguments to RPC functions
Add support for using keyword arguments with a named struct in an RPC
Add bootstrap method to TwoPartyServer
Add init method to lists
Add support for unix sockets in RPC

v0.5.6 (2015-04-13)

Fix a serious bug in TwoPartyServer that was preventing it from working when passed a string address.
Fix bugs that were exposed by defining KJDEBUG (thanks @davidcarne for finding this)

v0.5.5 (2015-03-06)

Update bundled C++ libcapnp to v0.5.1.2 security release

v0.5.4 (2015-03-02)

Update bundled C++ libcapnp to v0.5.1.1 security release
Add bootstrap RPC methods
Fix possible segfault when importing multiple schemas

v0.5.3 (2015-02-23)

Fix possible crash due to bad destructor ordering in MessageReader (by @JohnEmhoff)
Default to no longer using cython

v0.5.2 (2015-02-20)

Add read_multiple_bytes/read_multiple_bytes_packed methods
Added Python 3.4 to the travis build matrix
Bump version for bundled C++ libcapnp to v0.5.1

v0.5.1 (2014-12-27)

Remove installation dependency on cython. We now have no dependencies since libcapnp will automatically build as well.

v0.5.0 (2014-12-15)

Timer class capnp.getTimer()
pycapnp is now thread-safe and allows an event loop to be run in each thread

You must destroy and re-create the event loop to get this functionality (see test_threads.py)

Inheritance now works correctly for interfaces (previously inherited methods were inaccessible from pycapnp)
Add ability to import modules with dashes or spaces. Use underscores in place of them
from_bytes with builder=True is no longer zero copy. It never worked correctly, and is much safer now
Add num_first_segment_words argument wherever message creation can occur
Allow restoring a null objectId by passing None to restore
Support ordered dictionary in to_dict
Add ListSchema class and schemas for native types under capnp.types which completes all the Schemas needed to be wrapped. See test_schema.py for examples using it
Add automatic build of C++ libcapnp if it's not detected on the system. Also add flags --force-bundled-libcapnp and --force-system-libcapnp respectively

v0.4.6 (2014-9-10)

Fix build for new 0.21 release of Cython. 0.21 is now the minimum supported version of Cython.

v0.4.5 (2014-6-26)

Fix to_dict not converting enums to strings

v0.4.4 (2014-04-25)

Fix compilation problem with gcc 4.8

v0.4.3 (2014-02-18)

Fix problem with uninitialized unions in _from_dict
Add accesible version numbers for C++ libcapnp

v0.4.2 (2014-02-13)

Remove onDrained since it was removed upstream
Replace usage of strings as enum type with custom _DynamicEnum class.
Also change Struct.which() method to be a property Struct.which and return an enum type (_DynamicEnumField, which behaves much like _DynamicEnum).
TwoPartyServer.run_forever() now will handle more than 1 simulataneous connection.
Change exception wrapper to detect and raise AttributeError for field lookup exceptions (Fixes problem in Python3.x __dir__)
Allow setting of fields with python dicts.

0.4.1 (2013-12-18)

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 it and Python2.
Fix problems with null characters in Text/Data fields. Fixes #19

0.4.0 (2013-12-12)

Initial working version of RPC
Add get_root_as_any to _MessageReader
Add capnp.pxd for public declarations of cython classes
Fix problems compiling with gcc4.7

v0.3.18 (2013-11-05)

Change naming of ReaderOption parameters to be pep8 compliant

v0.3.17 (2013-11-05)

Add ReaderOptions to read/read_packed/from_bytes

v0.3.16 (2013-10-28)

Add defaults flag to capnp-json. Also remove 'which' field
Add capnp-json serializer script. Also fix bugs in from_dict
Fix build for clang/python3. Also remove -fpermissive
Add as_builder method to Struct Reader
Add warning when writing the same message more than once
First working version of capability interfaces
Wrap InterfaceSchema
Fix setting string fields to support all types of strings
Fix changed API for DynamicObject/ObjectPointer

v0.3.15 (2013-09-19)

Add not having installed the C++ libcapnp library to 'Common Problems'
Add _short_str function for use in capnp_test_pycapnp.py
Add test script for testing with https://github.com/kaos/capnp_test
Add handling of DynamicObject
Fix lists of lists or dicts for from_dict

v0.3.14 (2013-09-04)

Fix problem with to_dict

v0.3.13 (2013-09-04)

Add _DynamicStructBuilder.to_bytes() and .from_bytes()
Change == on StructSchema to return cbool
Add Builder and Reader ABCs for each struct type

v0.3.12 (2013-09-03)

Fix handling of empty path '' in load_module
Add from_dict
Fix bug in exception handling for which(). Also standardize exceptions.
Change import hook to require modules to end in '_capnp'
Add import monkey patch function.
Change naming for functions to conform to PEP 8. Also deprecate old read/write API
Update preferred method for reading/writing messages from files

v0.3.11 (2013-09-01)

Forgot to change project name in setup.py

v0.3.10 (2013-09-01)

Change all references to old project name (change from capnpc-python-cpp to pycapnp)
Change DynamicValue.Reader lists to be returned as _DynamicListReader
Unify setters for DynamicList and DynamicStruct
Add shortcuts for reading from / writing to files. In Python, it doesn't make much sense to force people to muck around with MessageReaders and MessageBuilders since everything is landing on the heap anyway. Instead, let's make it easy: MyType.read[Packed]From(file) reads a file and returns a MyType reader. MyType.newMessage() returns a MyType builder representing the root of a new message. You can call this builder's write[Packed]To(file) method to write it to a file.
Store Builders by value rather than allocate them separately on the heap (matches treatment of Readers). v0.3 fixes the bug that made this not work.
Wrap MessageBuilder::setRoot().
Add tests based on TestAllTypes from the C++ test.capnp. Fix problems uncovered in capnp.pyx.
Implement str and repr for struct and list builders. str uses prettyPrint while repr shows the type name and the low-whitespace stringification. Also implement repr for StructSchema, just because why not?

v0.3.9 (2013-08-30)

Change load to use a global SchemaParser. Make structs settable as field
Add docstrings for new functions and _DynamicResizableListBuilder

v0.3.8 (2013-08-29)

Add initial tests
Add _capnp for original Cython module. Meant for testing.
Lowercase schema so it conforms to member naming conventions
Expose _StructSchema's raw node
Add some useful _StructSchema, reader, and builder methods
Add full orphan functionality. Also, allow special orphan lists
Finish up adding docstrings to all public classes/methods

v0.3.7 (2013-08-26)

Add a ton of docstrings and add to official docs
Add DynamicOrphan

v0.3.6 (2013-08-26)

Add intersphinx for linking to python docs
Add C++ library version check

v0.3.5 (2013-08-25)

Add handling of constants in schemas
Fix new error with DynamicValue.Builder no longer being copyable

v0.3.4 (2013-08-22)

Fix Void namespace change
Updated capnp schema to conform with new union rules

v0.3.3 (2013-08-22)

Fix for the removal of DynamicUnion from the C++ API

v0.3.2 (2013-08-21)

Add MANIFEST.in to include README

v0.3.1 (2013-08-21)

Update docs with lines about upgrading setuptools

0.3.0 (2013-08-21)

Initial commit of docs
Add querying unnamed enums to structs

0.2.1 (2013-08-13)

Fix enum interface change for benchmark
Random formatting cleanup
Allow import paths in the schema loader
Add travis CI

0.2.0 (2013-08-12)

Initial working version