PyBash

Streamline bash-command execution from python with a new syntax. It combines the simplicity of writing bash scripts with the flexibility of python. Under the hood, any line or variable assignment starting with $ or surrounded by parentheses is transformed to python subprocess calls and then injected into sys.meta_path as an import hook. All possible thanks to the wonderful ideas project!

For security and performance reasons, PyBash will NOT execute as shell, unless explicitly specified with a > instead of a single $ before the command. While running commands as shell can be convenient, it can also spawn security risks if you're not too careful. If you're curious about the transformations, look at the unit tests for some quick examples.

Note: this is a mainly experimental library.

Setup

As standalone transformer

pip install pybash

from pybash.transformer import transform

transform("$echo hello world") # returns the python code for the bash command as string

As script runner

pip install "pybash[script]"

Example

text = "HELLO WORLD"
$echo f{text}

Run script:

python -m pybash hello.py

Supported transforms

1. Simple execution with output

$python --version
$echo \\nthis is an echo

outputs:

Python 3.9.15

this is an echo

2. Set output to variable and parse

out = $cat test.txt
test_data = out.decode('utf-8').strip()
print(test_data.replace("HELLO", "HOWDY"))

outputs:

HOWDY WORLD

3. Wrapped, in-line execution and parsing

print(($cat test.txt).decode('utf-8').strip())

outputs:

HELLO WORLD

4. Redirection

$echo "hello" >> test4.txt

5. Pipe chaining

$cat test.txt | sed 's/HELLO/HOWDY/g' | sed 's/HOW/WHY/g' | sed 's/WHY/WHEN/g'

outputs:

WHENDY WORLD

6. Redirection chaining

$cat test.txt | sed 's/HELLO/HOWDY\\n/g' > test1.txt >> test2.txt > test3.txt

7. Chaining pipes and redirection- works in tandem!

$cat test.txt | sed 's/HELLO/HOWDY\\n/g' > test5.txt

8. Input redirection

$sort < test.txt >> sorted_test.txt

$sort < test.txt | sed 's/SORT/TEST\\n/g'

9. Glob patterns with shell

>ls .github/*

10. Direct interpolation

Denoted by {{code here}}. Interpolated as direct code replace. The value/output of the variable, function call, or the expression must not include spaces.

## GOOD
command = "status"
def get_option(command):
    return "-s" if command == "status" else "-v"
$git {{command}} {{get_option(command)}}

display_type = "labels"
$kubectl get pods --show-{{display_type}}=true

## BAD
option = "-s -v"
$git status {{option}}

options = ['-s', '-v']
$git status {{" ".join(options)}}

# use dynamic interpolation
options = {'version': '-v'}
$git status {{options['version']}}

11. f-string interpolation

Denoted by f{ any python variable, function call, or expression here }. Interpolated as f-string. The output of the variable, function call, or the expression must still not include spaces.

## GOOD

# git -h
options = {'version': '-v', 'help': '-h'}
$git f{options['h']}

# kubectl get pods --show-labels -n coffee
namespace = "coffee"
$kubectl get pods f{"--" + "-".join(['show', 'labels'])} -n f{namespace}

## BAD
option = "-s -v"
$git status f{option}

Also works inside methods!

# PYBASH DEMO #
def cp_test():
    $cp test.txt test_copy.txt

cp_test()

Dev

Demo

python -m pybash examples/hello.py python -m pybash demo

Debug

make debug to view the transformed source code