scrolls-py 0.2.0

A customizable interpreted microlanguage designed to run untrusted code.

Scrolls

Scrolls is a small interpreter originally designed to allow users of my discord bots to make custom commands. It prioritizes control over the interpreter to help prevent abuse, while still allowing tight integration with python code.

Links

• Documentation: https://a-bison.github.io/scrolls-py-docs/
• Source Code: https://github.com/a-bison/scrolls-py
• PyPI: https://pypi.org/project/scrolls-py/

Why?

The two other candidates for user scripts were python and Lua. Python code is a nightmare to sandbox properly, and the available Lua interpreters for python didn't give me the kind of control I wanted over the interpreter. In addition, Lua was a bit much for simple custom commands. So, I made my own interpreter.

There is a scripting language available for Rust called Rhai with a similar concept.

Also, I just kinda wanted to try making an interpreted language...

Goals

• Allow the developer to prevent abuse.
• Integrate tightly with the parent python application.
• Keep the syntax as simple as possible.

Getting Started

Check out the Links section above.

Installing

Scrolls may be installed through pip:

Linux

python3 -m pip install scrolls-py

Windows

py -3 -m pip install scrolls-py

Command Line Usage

The module comes with a built-in interpreter that may be invoked by executing the module. (Note that the linux version will be used from now on.)

python3 -m scrolls FILE

Try running some of the examples:

python3 -m scrolls ./examples/arithmetic.scrl

If no file is specified, the interpreter will run in interactive mode:

python3 -m scrolls

Programmatic Usage

Scrolls may be embedded into any python program:

import scrolls

# Create an interpreter. Note that an interpreter created this 
# way will not actually do anything. It's the responsibility of 
# the user to configure with the desired language features.
interpreter = scrolls.Interpreter()

# Configure the interpreter with the base language.
# scrolls.base_config is provided to make this common task
# a bit easier.
scrolls.base_config.configure(interpreter)

# Configure with stdio commands like input, and print
interpreter.command_handlers.add(scrolls.StdIoCommandHandler())

# Run your script.
script = """
print "Please enter your name:"
input name
!repeat(4) {
    print "Hello," $(cat $name "!")
}
"""
interpreter.run(script)

Acknowledgements

• hikari-lightbulb by tandemdude, which inspired the CallBase extension (see here).