Flowbased Programming for Python
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rill is a lightweight python framework for Flow-based Programming built on gevent. With it, you can create networks of worker components, each operating on their own green thread, which push and pull streams of data packets through named ports.

The internals are heavily inspired by JavaFBP, which is maintained by the author of the seminal book on the subject, while the public API draws from concise and expressive frameworks like click and flask.


git clone https://github.com/chadrik/rill
cd rill
pip install .


The following example takes the string 'Hello Goodbye World', splits it into words, then filters out words that start with 'G' and joins the words back into a line.

from rill import inport, outport, component
from rill.engine.network import Network

def Output(IN, OUT):
    for p in IN:

@inport("IN", type=str)
@inport("TEST", type=str)
@outport("ACC", type=str)
@outport("REJ", type=str)
def StartsWith(IN, TEST, ACC, REJ):
    test_str = TEST.receive_once()

    for p in IN.iter_packets():
        s = p.get_contents()
        if s.startswith(test_str):

@inport("IN", type=str)
@inport("MEASURE", type=int)
@outport("OUT", type=str)
def WordsToLine(IN, MEASURE, OUT):
    measure = MEASURE.receive_once()

    line = ""
    for word in IN.iter_contents():
        if measure and (len(line) + 1 + len(word)) > measure:
            # restart line
            line = word
            if line:
                line += " "
            line += word
    if line:
        # remainder

@outport("OUT", type=str)
@inport("IN", type=str)
def LineToWords(IN, OUT):
    for line in IN.iter_contents():
        words = line.split()
        for word in words:

net = Network()
net.add_component("LineToWords", LineToWords, IN="HeLLo Goodbye World")
net.add_component("StartsWith", StartsWith, TEST='G')
net.add_component("WordsToLine", WordsToLine)
dis = net.add_component("Output", Output)

net.connect("LineToWords.OUT", "StartsWith.IN")
net.connect("StartsWith.REJ", "WordsToLine.IN")
net.connect("WordsToLine.OUT", "Output.IN")

Using the UI

rill can be started as a server, known as a runtime, that can communicate with clients such as UIs and other runtimes using the FBP Network Protocol. Currently, the primary UI that supports this open protocol is noflo-ui. There are still some incompatibilities between rill and noflo-ui that are being worked out, but if you want to give it a try, read on.


npm install -g n
npm install -g bower
npm install -g grunt-cli
sudo n 4.1

mkdir noflo
cd noflo

git clone https://github.com/noflo/noflo-ui
cd noflo-ui
git checkout 40acbb4d92f178837f161b7c15f2dde2a5bfa4bc
npm install
# running bower before grunt prompts to resolve a dependency conflict which otherwise causes grunt to fail
bower install
grunt build
python -m SimpleHTTPServer 8000


  1. Open your browser to http://localhost:8000/
  2. Log in using your github account. Go to "Settings" and copy your "User Identifier"
  3. In a fresh shell, cd into the root of the rill repo.
  4. Start the rill runtime.
    python -m rill.runtime --user-id <USER_ID>
  5. Back in the browser, create a new project in NoFlo selecting the rill runtime
  6. Green arrows should appear on the top-right menu, right before ws:\\localhost:3569