#capnpc-python-cpp

Downloading

For now, this code is only on github although I plan to put it up on PyPi at somepoint.

You can clone the repo like so:

git clone https://github.com/jparyani/capnpc-python-cpp.git

Requirements

First you need a system-wide installation of the Capnproto C++ library. All you need to do is follow the official installation docs]. Also on my ubuntu 12.10 box, I had to run sudo ldconfig after installation to make sure the libcapnp library was picked up by the linker.

You also need a working version of the latest Cython and the latest version of setuptools. This is easily done with:

pip install -U cython setuptools

Building and installation

cd into the repo directory and run python setup.py install or pip install .

Documentation/Example

At the moment, there is no documenation, but the library is almost a 1:1 clone of the Capnproto C++ Library

The examples directory has one example that shows off the capabilities quite nicely. Here it is, reproduced:

import capnp
addressbook = capnp.load('addressbook.capnp')

def writeAddressBook(fd):
    message = capnp.MallocMessageBuilder()
    addressBook = message.initRoot(addressbook.AddressBook)
    people = addressBook.initPeople(2)

    alice = people[0]
    alice.id = 123
    alice.name = 'Alice'
    alice.email = 'alice@example.com'
    alicePhones = alice.initPhones(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.initPhones(2)
    bobPhones[0].number = "555-4567"
    bobPhones[0].type = 'home'
    bobPhones[1].number = "555-7654" 
    bobPhones[1].type = addressbook.Person.PhoneNumber.Type.WORK
    bob.employment.unemployed = None

    capnp.writePackedMessageToFd(fd, message)

f = open('example', 'w')
writeAddressBook(f.fileno())

def printAddressBook(fd):
    message = capnp.PackedFdMessageReader(f.fileno())
    addressBook = message.getRoot(addressbook.AddressBook)

    for person in addressBook.people:
        print person.name, ':', person.email
        for phone in person.phones:
            print phone.type, ':', phone.number

        which = person.employment.which()
        print which

        if which == addressbook.Person.Employment.Which.UNEMPLOYED:
            print 'unemployed'
        elif which == addressbook.Person.Employment.Which.EMPLOYER:
            print 'employer:', person.employment.employer
        elif which == addressbook.Person.Employment.Which.SCHOOL:
            print 'student at:', person.employment.school
        elif which == addressbook.Person.Employment.Which.SELF_EMPLOYED:
            print 'self employed'
        print

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

PyPy

There is also a preliminary branch that works for pypy. Unfortunately it requires some pretty terrible hacks to get working, so you I've left it in it's own branch. Just do git checkout pypy and then install like normal pypy setup.py install or pip install .. Don't forget to install dependencies beforehand with pip install -U cython setuptools