py-sh

A binary for during your shell grunt work in python

Overview

Here's the value of py-sh, compared with bash and plain python

baseName="kai"

# with bash / coreutils
baseName="$(tr '[:lower:]' '[:upper:]' <<< ${baseName:0:1})${baseName:1}"
adminProfileSuffix="AdminRole"
adminProfile="$baseName$adminProfileSuffix"
echo $adminProfile # outputs "KaiAdminRole"

# with python
adminProfile=$(python -c "print('$baseName'.capitalize() + 'AdminRole')")
echo $adminProfile # outputs "KaiAdminRole"

# with py-sh
adminProfile=$(echo $baseName | py-sh 'input.capitalize() + str(AdminRole)')
echo $adminProfile # outputs "KaiAdminRole"

Status

py-sh version 1.0 is...

1%

...implemented.

Background

I do a lot of lightweight work with bash + coreutils, and doing that work requires looking up at least one stackoverflow question essentially 100% of the time. This is more or less caused by bash + coreutils having very esoteric syntax, and not directly catering to the specific needs of engineers working on cli. So you end up having to do things like this

baseName="kai"
baseName="$(tr '[:lower:]' '[:upper:]' <<< ${baseName:0:1})${baseName:1}"
adminProfileSuffix="AdminRole"
adminProfile="$baseName$adminProfileSuffix"
echo $adminProfile # outputs "KaiAdminRole"

That took me two stackoverflow searches to create, and uses a lot of syntax and assumptions that are hard to explain to new engineers.

At the same time, I already know python. I know offhand that in python, the equivalent functionality could be written on the terminal as

baseName="kai"
adminProfile=$(python -c "print('$baseName'.capitalize() + 'AdminRole')")
echo $adminProfile # outputs "KaiAdminRole"

I could create this with knowledge I had on hand! This is a nice boost to my iteration pace, is more readable for my future self, and uses syntax that you're very likely to see when doing other work in python.

It has a few significant flaws, though. In order of increasing importance:

• There's still quote a bit of "shell invocation boilerplate", in the ', ", -c. This is tedious most of the time, but quotes can cause issues with more complex input types.
• The advantage that python has over bash wanes when you start working with more complex input types, like files.
• Its excuting a string ($baseName) as arbitrary python code, which is a very easy way to cause a lot of security vulnerabilites.

That sucks. But wait... those are all engineering problems, and maybe all problems that can be solved???

The Goal

Spoiler: yes we can solve all those problems! We can create something that:

• Assumes its primary operating mode will be in a shell
• Includes builtin handling for files, including files of various data types
• Strictly handles its input types

I'm calling that thing py-sh, and I want it to work like this

baseName="kai"
adminProfile=$(echo $baseName | py-sh 'input.capitalize() + str(AdminRole)')
echo $adminProfile # outputs "KaiAdminRole"

Prior Art

The overarching goal of py-sh is very similar to xonsh, and ipython shell. All 3 (py-sh, xonsh, ipython shell) aim to give users to ability to do "shell work" using python. The contrast significantly in their conceptual API though, py-sh is meant to be executed inside your existing shell (eg bash, zsh, etc) - and xonsh / ipython shell want to replace your shell.

• Finding out about xonsh is what originally inspired to author to start exploring this concept 🗺
• Adding support for ipython's concept of magic commands is currently under consideration 📝

The API of py-sh is functionally identical to rb. The primary difference is in the implementation details, in that py-sh aims to ship itself as a binary that also contains a statically linked binary of its underlying language (eg. python).

• The idea to require api input be piped into py-sh was inspired by rb ✨