The shell adder

shelladder enables you to call Python functions as if they were Bash
functions or commands.

Calling print() in your Python function is directly sent to stdout. You can
pipe input into your functions, which can read it using sys.stdin.

Also, all the arguments are available in sys.argv, so you can use
argparse.ArgumentParser objects directly.

Named after the common European adders, which have a zigzag pattern on their
backs - just like what shelladder does, moving you from Bash into Python then
back into Bash, back and forth.

How it works

You begin by writing your Python functions in a module, e.g. myfunctions.py.
This module must not contain the usual construct if __name__ == "__main__".
Just write the functions, because shelladder will handle their calling.

Let's say you would like a Python function called printdir() to be accessible
to you in the terminal, as if it were a normal command. You would write a file
containing this:

import os

# export
def printdir():
    print(os.getcwd())

Note the # export line just above the line def printdir():. Adding # export before defining a function marks it for export into Bash, so
shelladdder knows you want to call it. Function definitions that don't have
the # export mark will remain "private" to the module, i.e. they can be
called by other exported functions, but not from Bash.

Once you're happy with your Python functions, save your file. For example,
myfunctions.py in your current folder. Now run this command:

python3 /some/where/shelladder/shelladder.py myfunctions.py

Now shelladder has created a new dot-folder in your $HOME called
.shelladder, where it will deploy your myfunctions.py module (with minor
modifications!), and it will create a companion Bash script, called
myfunctions.sh.

And by sourcing myfunctions.sh into your shell, you gain access to
all the # export-ed functions in myfunctions.py. Neat, right? Take a look at
these two generated files, to see what happened.

Now try sourcing:

source ~/.shelladder/myfunctions.sh

Try calling printdir now!

printdir
/what/ever/your/dir/is

A shortcut

Observe that shelladder will print the location of this companion Bash
script, which allows you to do everything in one command:

source $(python3 /some/where/shelladder/shelladder.py myfunctions.py)

Just make sure you run the above command everytime you edit myfunctions.py.

You need to specify the path to shelladder.py, because it's just a Python
script, not an executable. Or add an alias to ~/.bashrc:

alias adder="python3 /some/where/shelladder/shelladder.py"

Now you can do adder myfunctions.py anytime, from anywhere, hassle-free:

source $(adder myfunctions.py)
printdir
/what/ever/your/dir/is