JavaScript has an early proposal for this use-case: https://github.com/tc39/proposal-partial-application#pipeline-and-partial-application where "cat data | sort | cut -d; -f6 | grep ^foo | sort -r | uniq -c" could be represented as: data |> sort |> cut(?, delimeter=";", fields=6) |> grep(?, "^foo") |> sort(?, reverse=True) |> uniq(?, count=True)
A very similar operator already exists for Hack which has served to clean up a lot of code at Facebook: https://docs.hhvm.com/hack/expressions-and-operators/pipe ( fun fact: I was one of the people who asked for __matmul__ back in the day, but now I prefer the pipeline operator as it's not restricted to unary functions and is, IMHO, more readable https://mail.python.org/archives/list/python-ideas@python.org/message/I4DXFR4P5KAMHDL4MRAM43QCUMW4MIJY ) On Sun, May 24, 2020 at 7:33 PM David Mertz <me...@gnosis.cx> wrote: > On Sun, May 24, 2020 at 6:56 PM Steven D'Aprano <st...@pearwood.info> > wrote: > >> > I use bash a lot, and writing something like this is common: >> > cat data | sort | cut -d; -f6 | grep ^foo | sort -r | uniq -c >> >> And today's "Useless Use Of cat Award" goes to... :-) >> >> sort data | ... >> >> (What is it specifically about cat that is so attractive? I almost >> certainly would have done exactly what you did, even knowing that sort >> will take a file argument.) >> > > This is probably going afield since it is a bash thing, not a Python > thing. But I can actually answer this quite specifically. > > When I write a pipeline like that, I usually do not do it in one pass. I > write a couple of the stages, look at what I have, and then add some more > stages until I get it right. Many of the commands in the pipeline can take > a file argument (not just sort, also cut, also grep, also uniq... > everything I used in the example). > > But I find fairly often that I need to add a step BEFORE what I initially > thought was first processing step. And then I have to remove the filename > as an argument of that no-longer-first step. Rinse and repeat. With `cat` > I know it does nothing, and I won't have to change it later (well, OK, > sometimes I want -n or -s). So it is a completely generic "data" object > ... sort of like how I would write "fluent programming" starting with a > Pandas DataFrame, for example, and calling chains of methods.. > > -- > The dead increasingly dominate and strangle both the living and the > not-yet born. Vampiric capital and undead corporate persons abuse > the lives and control the thoughts of homo faber. Ideas, once born, > become abortifacients against new conceptions. > _______________________________________________ > Python-ideas mailing list -- python-ideas@python.org > To unsubscribe send an email to python-ideas-le...@python.org > https://mail.python.org/mailman3/lists/python-ideas.python.org/ > Message archived at > https://mail.python.org/archives/list/python-ideas@python.org/message/7DRNTPAWCU5SA666E6ZLEXZQVUYCS7VN/ > Code of Conduct: http://python.org/psf/codeofconduct/ >
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