you could reassign every line, but it would look nicer with chained functions.

  pipeline = task(get_data, branch=True)
  pipeline = pipeline | task(step1, workers=20)
  pipeline = pipeline |  task(step2, workers=20)
  pipeline = pipeline |  task(step3, workers=20, multiprocess=True)

I would be tempted to do something like this:

  steps = [task(step1, workers=20),
           task(step2, workers=20),
           task(step3, workers=20, multiprocess=True)]
  pipeline = task(get_data, branch=True)

  for step in steps:
      pipeline =   pipeline.__or__(step)

  pipeline = task(get_data, branch=True).pipe(
      task(step1, workers=20)).pipe(
      task(step2, workers=20)).pipe(
      task(step3, workers=20, multiprocess=True))

    pipeline = task(...)
    pipeline |= task(...)

    steps = [task(...), task(...)]
    pipeline = functools.reduce(operator.or_, steps)

    pipeline = pyper.Pipeline([Task(...), Task(...)])

I've not been doing Python day-to-day so I'm starting to lose my touch on all the nice little tricks.

pipeline = (

    task(get_data, branch=True)

    | task(step1, workers=20)

    | task(step2, workers=20)

    | task(step3, workers=20, multiprocess=True)

Square brackets would create a list and braces would create a set of course. The contents still can be split over different lines-- just pointing that this syntax doesn't do the same thing.