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But why would you, when you can just do subprocess.popen on the command and then slice and dice the result in a language that can do regexes, splitting, format

But why would you, when you can just do subprocess.popen on the command and then slice and dice the result in a language that can do regexes, splitting, format strings, and so forth? I mean, if you're going to be using Python anyways, you might as well just use the standard library and skip the extra bash step entirely. The code might be a bit longer, but infinitely safer and more maintainable.

yorwba 9y ago
If all you're doing is rewriting the pipelines you'd have written in Bash using subprocess in Python, you're not making your code safer or more maintainable. Unless I'm missing something, subprocess.Popen requires you to explicitly wire up the inputs and outputs, whereas Bash has clear and readable syntax for the most common idioms. For a program that mostly just calls other programs with the right parameters, Python only obfuscates the important bits with details that a shell abstracts away. For a program that has to do some non-trivial processing, pure Bash+coreutils definitely loses to a general-purpose programming language with good standard library. But that doesn't mean that you have to completely switch over. You can leave the parts in Bash that are just pipelines of other programs (again, Python can't improve anything there) and do your further processing in Python. Whether that's implemented as a Bash script calling Python in a pipeline or Python delegating part of it's processing to a Bash script just depends on the most natural entry point. It might feel "impure" to mix two different languages in a program, but I think using each language in the domain where it's strengths shine is a much better idea than attempting to emulate the core features of one language in the other.
- mbrock 9y ago
  Often it's a really nice and interesting exercise to approach a problem by thinking along the lines of: "This shell script is a bit complex. Instead of rewriting the shell script in another language, is there some simple and standalone way I could massage the data, in order to make the shell script simple again?" It's quite a lot like thinking like this: "This Python script is getting a bit slow. Instead of rewriting it in a faster language, is there some little part of it that I could isolate and only write that in a faster language?"

yorwba 9y ago

If all you're doing is rewriting the pipelines you'd have written in Bash using subprocess in Python, you're not making your code safer or more maintainable. Unless I'm missing something, subprocess.Popen requires you to explicitly wire up the inputs and outputs, whereas Bash has clear and readable syntax for the most common idioms. For a program that mostly just calls other programs with the right parameters, Python only obfuscates the important bits with details that a shell abstracts away. For a program that has to do some non-trivial processing, pure Bash+coreutils definitely loses to a general-purpose programming language with good standard library. But that doesn't mean that you have to completely switch over. You can leave the parts in Bash that are just pipelines of other programs (again, Python can't improve anything there) and do your further processing in Python. Whether that's implemented as a Bash script calling Python in a pipeline or Python delegating part of it's processing to a Bash script just depends on the most natural entry point. It might feel "impure" to mix two different languages in a program, but I think using each language in the domain where it's strengths shine is a much better idea than attempting to emulate the core features of one language in the other.

mbrock 9y ago
Often it's a really nice and interesting exercise to approach a problem by thinking along the lines of: "This shell script is a bit complex. Instead of rewriting the shell script in another language, is there some simple and standalone way I could massage the data, in order to make the shell script simple again?" It's quite a lot like thinking like this: "This Python script is getting a bit slow. Instead of rewriting it in a faster language, is there some little part of it that I could isolate and only write that in a faster language?"