PyCOM is simple and easy-to-use distributed component model written in Python. PyCOM makes different parts of your network application isolated and independent, while allowing easy and straightforward interaction between them. PyCOM may be seen as an easy and lightweight web services replacement.

Ideology highlights:

  • Non-intrusive design without black magic and lots of auto-generated code
  • Easily adapts to a rapidly changing environment
  • ... and matches pythonic EAFP approach
  • Effective, easy-to-implement and portable protocol
  • Support for binary attachments
  • Support for stateful services via HTTP-alike sessions
  • Low level enough to build your own frameworks
  • ... and still simple enough to be used as is
  • Free software (new BSD license)

Technical highlights:

  • Separate (potentially replaceable) ZeroJSON protocol implementation
  • Easily extensible core library
  • Does not required special "container" software
  • Introspection support for services
  • Load balancing over several services with the same interface
  • Comprehensive test suite and documentation
  • Python 2 and Python 3 support out-of-box

There is ongoing effort to create a C++ client library for PyCOM:

Main concepts

With PyCOM you build your application as a number of services, each running in it's own process (or even on it's own computer). You maintain a PyCOM nameserver for finding services by their names (by the way, nameserver itself is a service).

Services provide interfaces, i.e. a named way of interacting with service. They are somewhat similar to interfaces in e.g. Java, but note that PyCOM does not perform any checks on interfaces. Interface usually has some amount of methods.

Services are identified by path with parts separated by slashes, e.g. /com/foo/group/service.

Interfaces are identified by name with parts separated by dots, e.g.


Service example (module package1.module1):

import pycom

class MyService(pycom.Service):

    def bar(self, request, name, value=None):
        return {name : value}

Example command line for running this service (provided nameserver is running on

pycom-launcher -a tcp:// -n tcp:// package1.module1

Example client code for this service:

import pycom

context = pycom.ProxyContext(nameserver="tcp://")
with context.locate("") as component:
    print"field1", value=42)
    # Prints {"field1" : 42}
    print"field1", value=42)
    # Prints {"field1" : 42}
    # Prints {"field1" : None}
    print component.introspect()
    # Prints a lot of introspection information

Quick start

Our requirements are:

  • POSIX-compatible OS (other may work)
  • Python 2.6, 2.7 or >= 3.1
  • 0MQ Python bindings >= 2.1.11
  • six for Python 3 compatibility (maybe we'll drop it later)
  • SimpleJSON is recommend for faster JSON parsing

Our service browser is a web application and requires:

To run test suite you'll also need:

To test (logs will be saved in test.log):

$ python

To build HTML documentation (requires Sphinx):

$ python build_sphinx
$ <your-browser> build/sphinx/html/index.html

To install from sources:

$ python install

or via pip:

$ pip install pycom

You can also use :download:`pip-requires.txt <../pip-requires.txt>` from the top of the source tree:

$ pip install -r /path/to/pip-requires.txt

To start nameserver use script:

$ /usr/local/bin/pycom-nameserver

You may need to adjust nameserver configuration.

Do not forget to read about known issues in the current version:


PyCOM repository and issue tracker are hosted on BitBucket.

Download releases:

Latest source code:

Report bugs:

Read documentation:

Enjoy =)