Re: Bash-like pipes in Python

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From	Joel Goldstick <joel.goldstick@gmail.com>
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Subject	Re: Bash-like pipes in Python
Date	Wed, 16 Mar 2016 11:09:04 -0400
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On Wed, Mar 16, 2016 at 10:57 AM, Steven D'Aprano <steve@pearwood.info>
wrote:

> There's a powerful technique used in shell-scripting languages like bash:
> pipes. The output of one function is piped in to become the input to the
> next function.
>
> According to Martin Fowler, this was also used extensively in Smalltalk:
>
> http://martinfowler.com/articles/collection-pipeline/
>
> and can also be done in Ruby, using method chaining.
>
> Here is a way to do functional-programming-like pipelines to collect and
> transform values from an iterable:
>
> https://code.activestate.com/recipes/580625-collection-pipeline-in-python/
>
> For instance, we can take a string, extract all the digits, convert them to
> ints, and finally multiply the digits to give a final result:
>
> py> from operator import mul
> py> "abcd12345xyz" | Filter(str.isdigit) | Map(int) | Reduce(mul)
> 120
>
>
> (For the definitions of Filter, Map and Reduce, see the code at the
> ActiveState recipe, linked above). In my opinion, this is much nicer
> looking that the standard Python `filter`, `map` and `reduce`:
>
> py> reduce(mul, map(int, filter(str.isdigit, "abcd12345xyz")))
> 120
>
> as this requires the operations to be written in the opposite order to the
> order that they are applied.
>
>
> This is interesting, but the part I'm missing is the use of the Pipe
symbol '|' in python.  Can you elaborate

>
> --
> Steven
>
> --
> https://mail.python.org/mailman/listinfo/python-list
>



-- 
Joel Goldstick
http://joelgoldstick.com/ <http://joelgoldstick.com/stats/birthdays>
http://cc-baseballstats.info/

Thread

Bash-like pipes in Python Steven D'Aprano <steve@pearwood.info> - 2016-03-17 01:57 +1100
  Re: Bash-like pipes in Python Joel Goldstick <joel.goldstick@gmail.com> - 2016-03-16 11:09 -0400
    Re: Bash-like pipes in Python Christian Gollwitzer <auriocus@gmx.de> - 2016-03-16 16:16 +0100
  Re: Bash-like pipes in Python Random832 <random832@fastmail.com> - 2016-03-16 11:20 -0400
    Re: Bash-like pipes in Python Steven D'Aprano <steve@pearwood.info> - 2016-03-17 21:58 +1100
      Re: Bash-like pipes in Python Marko Rauhamaa <marko@pacujo.net> - 2016-03-17 13:49 +0200
        Re: Bash-like pipes in Python Sivan Greenberg <sivan@vitakka.co> - 2016-03-17 14:10 +0200
          Re: Bash-like pipes in Python Marko Rauhamaa <marko@pacujo.net> - 2016-03-17 14:44 +0200
  Re: Bash-like pipes in Python "Sven R. Kunze" <srkunze@mail.de> - 2016-03-16 16:20 +0100
  Re: Bash-like pipes in Python Random832 <random832@fastmail.com> - 2016-03-16 11:21 -0400
  Re: Bash-like pipes in Python Steven D'Aprano <steve@pearwood.info> - 2016-03-17 02:39 +1100
  Re: Bash-like pipes in Python Marko Rauhamaa <marko@pacujo.net> - 2016-03-16 19:04 +0200
    Re: Bash-like pipes in Python Steven D'Aprano <steve@pearwood.info> - 2016-03-18 01:10 +1100
      Re: Bash-like pipes in Python Chris Angelico <rosuav@gmail.com> - 2016-03-18 01:36 +1100
      Re: Bash-like pipes in Python Random832 <random832@fastmail.com> - 2016-03-17 12:31 -0400
      Re: Bash-like pipes in Python Sivan Greenberg <sivan@vitakka.co> - 2016-03-17 19:20 +0200

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