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0 pointsklibertp7y ago0 comments

> Python REPL is an incredibly poor UI for repeated execution of subprocesses

Python REPL, even with recent additions of TAB completion, is a poor REPL, period.

IPython, on the other hand, offers a much better programming environment than shell while still allowing easy access to most of the things you mention. Example:

    In [1]: from pathlib import Path
    In [2]: file = Path("~/.sbclrc").expanduser().read_text()
    In [3]: !echo "$file" | awk '!/^;;/'   # EDIT: to clarify, this shows passing
                                           # Python variable to a shell pipeline.

    #-quicklisp
    (let ((quicklisp-init (merge-pathnames quicklisp/setup.lisp
                                           (user-homedir-pathname))))
      (when (probe-file quicklisp-init)
        (load quicklisp-init)))

All things considered, between !, %, %% and /, IPython is a decent shell. I was using it for a few years as my main shell, actually - its QT Console implementation specifically. I was working on Windows back then, PowerShell didn't exist yet, and `cmd.exe` was... well, exactly the same as today.

TLDR: a shell is just a REPL with a few conveniences for specific tasks. Re-implement these and suddenly any REPL becomes a workable shell.

0 comments

palunon7y ago

> In [3]: !echo "$file" | awk '!/^;;/'

That's Bash (or at least sh). Which excels at piping the output of programs into other programs, and pay that cost for everything else.

klibertpOP7y ago

Yeah, that's what I mean by "easy access" - you're working with Python, but if you want to do something that Python is not well-suited for[1] - like easily piping something through many programs - you can do it simply by adding `!` at the beginning of your pipeline, right there in the REPL.

It's actually the same philosophy that shells use: in bash you frequently invoke sed, awk, grep, etc. because it's easier than writing the same directly in the shell. In IPython, you invoke bash to do piping, because it's easier than connecting a host of subprocesses' stdins/stdouts in Python.

So again, there are some things you expect from your shell, and as long as you get those things (no matter how), you can use any REPL as a shell without problems.

[1] because of syntax or lack of library or something like that

wlib7y ago

Piping program output is just function composition. The downside is that it works over expensive system processes, and data must be serialized. It's a fragile system where instead of using built-in functions, we use "standard" executables.

yesenadam7y ago

I think, rather, function composition is just piping program output.

dbdjfjrjvebd7y ago

Yep. IPython lets you execute bash.

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