Agfdhyk

If I have an input queue with 20 numbers, how can I get e.g. the sum of all numbers? So far this is what I came up with:

import bonobo as bb

from bonobo.config import Configurable, ContextProcessor

from bonobo.util import ValueHolder



def extract_nums():

    yield 1

    yield 2

    yield 3



class TransformNumber(Configurable):

    @ContextProcessor

    def total(self, context):

        yield ValueHolder({'extract':0,'transform':0})



    def __call__(self, total, num, **kwargs):

        total['extract']+=num

        transform_num = num * 10

        total['transform']+=transform_num

        if num==3: # Final number

            print("TOTALS:",total.get())

        yield transform_num



graph = bb.Graph()

graph.add_chain(

    extract_nums,

    TransformNumber(),

    bb.PrettyPrinter()

)

It is ok to do it like this or is there a better way?

There are different available options to keep local state in a Bonobo ETL node.

It's ok to do it like you did (although I think it's hard to read), I tend to prefer to use closures which I think are more readable (but I agree, that's debatable):

import bonobo





def CumSum():

    total = 0



    def cum_sum(x):

        nonlocal total

        total += x

        yield x, total



    return cum_sum





def get_graph(**options):

    graph = bonobo.Graph()

    graph.get_cursor() >> range(100) >> CumSum() >> print



    return graph





# The __main__ block actually execute the graph.

if __name__ == "__main__":

    parser = bonobo.get_argument_parser()

    with bonobo.parse_args(parser) as options:

        bonobo.run(get_graph(**options))

A few examples are available in the bonobo source code, please look in https://github.com/python-bonobo/bonobo/blob/develop/bonobo/nodes/basics.py (and there are examples written in different styles).

Note that I'm using the Bonobo 0.7 (incoming) syntax here to build the graph, but the same thing can be used with current stable version (0.6) by replacing ">>" operators by add_chain calls.