embedding

README

Embedding gpython

This is an example demonstrating how to embed gpython into a Go application.

Why embed gpython?

Embedding a highly capable and familiar "interpreted" language allows your users to easily augment app behavior, configuration, and customization -- all post-deployment.

Have you ever discovered an exciting software project but lost interest when you had to also learn its esoteric language schema? In an era of limited attention span, most people are generally turned off if they have to learn a new language in addition to learning to use your app.

If you consider why use Python, then perhaps also consider that your users will be interested to hear that your software offers even more value that it can be driven from a scripting language they already know.

Python is widespread in finance, sciences, hobbyist programming and is often endearingly regarded as most popular programming language for non-developers. If your application can be driven by embedded Python, then chances are others will feel excited and empowered that your project can be used out of the box and feel like familiar territory.

But what about the lack of python modules?

There are only be a small number of native modules available, but don't forget you have the entire Go standard library and any Go package you can name at your fingertips to expose!
This plus multi-context capability gives gpython enormous potential on how it can serve you.

So basically, gpython is only off the table if you need to run python that makes heavy use of modules that are only available in CPython.

Packing List

main.go	if no args, runs in REPL mode, otherwise runs the given file
lib/mylib.py	models a library that your application would expose for users
lib/REPL-startup.py	invoked by main.go when starting REPL mode
testdata/mylib-demo.py	models a user-authored script that consumes mylib
mylib.module.go	Go implementation of mylib_go consumed by mylib

Invoking a Python Script

$ cd examples/embedding/
$ go build .
$ ./embedding ./testdata/mylib-demo.py

Welcome to a gpython embedded example, 
    where your wildest Go-based python dreams come true!

==========================================================
        Python 3.4 (github.com/B9O2/gpython)
        go1.17.6 on darwin amd64
==========================================================

Spring Break itinerary:
    Stop 1:   Miami, Florida    |   7 nights
    Stop 2:   Mallorca, Spain   |   3 nights
    Stop 3:   Ibiza, Spain      |  14 nights
    Stop 4:   Monaco            |  12 nights
###  Made with Vacaton 1.0 by Fletch F. Fletcher 

I bet Monaco will be the best!

REPL Mode

$ ./embedding

=======  Entering REPL mode, press Ctrl+D to exit  =======

==========================================================
        Python 3.4 (github.com/B9O2/gpython)
        go1.17.6 on darwin amd64
==========================================================

>>> v = Vacation("Spring Break", Stop("Florida", 3), Stop("Nice", 7))
>>> print(str(v))
Spring Break, 2 stop(s)
>>> v.PrintItinerary()
Spring Break itinerary:
    Stop 1:   Florida           |   3 nights
    Stop 2:   Nice              |   7 nights
###  Made with Vacaton 1.0 by Fletch F. Fletcher 

Takeways

• main.go demonstrates high-level convenience functions such as py.RunFile().
• Embedding a Go struct as a Python object only requires that it implement py.Object, which is a single function: Type() *py.Type
• See py/run.go for more about interpreter instances and py.Context
• Helper functions are available in py/util.go and your contributions are welcome!