Minimal python scripting language

README.md

Minimal Python scripting language

The example contains just a simple command interpreter for setting, getting, and persisting variables. It is meant as a demo that could be extended with more commands and more complex functionality to use in for instance ROS2.

Uses a command lookup system (COMMANDS dictionary) to map user input to the appropriate functions and execute them. The user interacts with the program through a basic REPL (Read-Eval-Print Loop) in the command_loop().

Commands:

• help : Print information about commands
• set <var_name> <value>: Set a variable with a given name to a specific value.
• get <var_name>: Retrieve and print the value of a variable.
• save <path>: Save the current state of variables to a JSON file.
• load <path>: Load the variables' state from a previously saved JSON file.

Example Usage:

>> set x 10
>> get x
10
>> save example.json
>> set x 100
>> get x
100
>> load example.json
>> get x
10

main.py

# Minimal python scripting language which can be used as a starting off point
import json

VARIABLES = {}

def set_var(name: str, val) -> None:
    """ Set the value of a variable, e.g. `set pi 3.14`"""
    VARIABLES[name] = val

def get_var(name: str):
    """ Print the value of a stored variable """
    if name in VARIABLES:
        print(VARIABLES[name])

def save(name: str) -> None:
    """ Save the current configuration to a json file with a given name """
    json.dump(VARIABLES, open(name, 'w'))

def load(name: str) -> None:
    """ Load a configuration json by name """
    global VARIABLES
    VARIABLES = json.load(open(name))


def print_help() -> None:
    """ Print this help window """
    for name, fn in COMMANDS.items():
        print(f"- {name:<10}:{fn.__doc__}")


COMMANDS = {
    "help" : print_help,
    "set" : set_var,
    "get" : get_var,
    "save" : save,
    "load" : load,
}

def command_loop():
    while True:
        try:
            user_input = input(">> ")
            
            parts = user_input.split()
            if len(parts) == 0:
                continue

            command_name = parts[0]
            args = parts[1:]

            COMMANDS[command_name](*args)
        
        except Exception as e:
            print(f"Error: {e}")


if __name__ == "__main__":
    command_loop()