Technical Note: Combining Python Scripting with MUD-Specific Commands for a Game Environment

Introduction

In this technical note, we aim to create a flexible language integration for a MUD (Multi-User Dungeon) game that leverages Python scripting for complex logic while maintaining a simplified command-based syntax for in-game actions like go west or say hello. We want to clearly separate the game’s commands from the programming logic, with commands acting as a streamlined interface for players, and Python providing the more complex logic for game mechanics or AI behaviors.

Key Goals

1. Streamlined Command Syntax: Maintain a simple, intuitive syntax for in-game commands like go west, say hello, look at door, without requiring the user to write Python code for these actions.
2. Python Scripting: Provide Python as a powerful tool for more complex in-game logic, scripting events, NPC (non-player character) behaviors, or managing game mechanics.
3. Separation of Concerns: Ensure that basic player commands are separate from the programming logic, reducing complexity for users interacting with the game.

Problem Definition

Commands like go west or say hello are intuitive and expected in text-based MUDs. However, Python’s syntax (go('west') or say('hello')) is too verbose and technical for casual gameplay. We want:

• Simple, natural language commands for basic actions.
• Python programming for advanced game logic and scripting behind the scenes.

The challenge is to enable both in a single system while keeping them logically distinct.

---

1. Streamlining Built-in Commands

Command-Only Syntax

We will simplify the command system to focus on core MUD actions like movement, interactions, and combat. Instead of a full programming language for these commands, we’ll treat them as direct inputs interpreted by the game engine.

Basic Command Format

Instead of using Python syntax for in-game commands, we will directly accept natural-language-style inputs from players:

go west
say hello there, how goes it!
look at door
pick up sword
attack goblin

These commands should be parsed directly by the game engine, not Python. The game engine will match each input against a list of known commands and execute them accordingly.

---

2. Parsing Commands in the MUD Engine

To handle this natural command input, the game engine needs a parser that can interpret player commands without needing to follow Python’s strict syntax.

Command Parsing Example

We can implement a simple parser to process the input strings, identify the commands, and invoke the corresponding functions in the game engine.

// A basic command parser in C# or similar
string input = "go west";  // Example command
string[] words = input.Split(' ');  // Split input into words

string command = words[0];  // First word is the command
string[] args = words.Skip(1).ToArray();  // Remaining words are arguments

switch (command.ToLower())
{
    case "go":
        string direction = args[0];
        player.Move(direction);
        break;

    case "say":
        string message = string.Join(' ', args);
        player.Say(message);
        break;

    // Add more cases for other commands...
}

In this example, the parser splits the input into the command (e.g., go, say) and its arguments (e.g., west or a message). This approach keeps command parsing simple and player-friendly.

Handling Complex Inputs

For more complex commands, such as look at door or pick up sword, we can extend the parser to handle multi-word commands and objects:

if (command == "look" && args[0] == "at")
{
    string target = args[1];
    player.LookAt(target);
}

By handling multi-word commands and special cases like look at or pick up, we can keep the input simple while allowing a wide range of interactions.

---

3. Python Scripting for Complex Logic

While player commands will be simple, the game logic and advanced scripting will rely on embedded Python scripts for complex behaviors. This is where IronPython comes into play.

Separate Python Logic

For Python scripting, we will allow Python code to be used for tasks such as:

• NPC behaviors: Script how NPCs react to player actions, move around the world, or engage in combat.
• Event triggers: Write Python scripts to handle in-game events, like quests or puzzles.
• Game logic: Implement game-wide mechanics or AI logic.

Example: Python NPC Behavior

Here's an example of how we might script NPC behavior in Python:

# Python script for NPC behavior
def on_player_nearby(player, npc):
    if npc.is_hostile:
        npc.attack(player)
    else:
        npc.say("Greetings, traveler.")

This script runs in response to a player approaching an NPC. It checks the NPC’s hostility status and either engages in combat or initiates dialogue.

---

4. Accessing Game Data in Python

IronPython allows us to access and manipulate game objects from Python scripts. By passing in game objects (like player or world) to the Python environment, we can give scripts the ability to interact with the game state.

Exposing Game Objects to Python

We can pass the relevant game objects into the Python runtime:

// C# example of passing game objects into IronPython
ScriptEngine engine = Python.CreateEngine();
ScriptScope scope = engine.CreateScope();

scope.SetVariable("player", player);
scope.SetVariable("npc", npc);
scope.SetVariable("world", world);

This makes the game objects available within Python, where they can be accessed and modified by scripts.

Example: Python Script to Modify Game Data

In the Python environment, game data can be modified just like any other object:

# Python script example
player.health -= 20
npc.say("You look hurt! Be careful.")

Here, the player’s health is reduced, and the NPC reacts by saying a predefined message.

---

5. Combining Commands and Python Logic

The final challenge is to integrate these two systems—simple commands and Python scripting—seamlessly.

Handling Commands and Scripts Together

The game engine can treat commands like go west or say hello as direct inputs, while Python handles more complex logic. The key is keeping them separate yet allowing them to interact when needed.

Example: Triggering a Python Script from a Command

In certain situations, a command might trigger a Python script. For example, the attack goblin command could invoke a Python script to handle the goblin’s behavior:

switch (command.ToLower())
{
    case "attack":
        string target = args[0];
        npc = world.FindNpc(target);
        if (npc != null)
        {
            engine.ExecuteFile("scripts/attack_goblin.py", scope);
        }
        break;
}

In this case, when a player attacks a goblin, the attack_goblin.py script is executed in IronPython to manage the goblin’s response.

---

Conclusion

By combining a streamlined command system with embedded IronPython scripting, we can create a flexible yet simple MUD game environment. Players can issue commands like go west or say hello without needing to know Python syntax, while game developers and AI scripts can leverage Python for complex behaviors and logic. This dual approach allows for a natural interaction with the game world while maintaining the power and flexibility of a full scripting environment.

• Commands like go, look, and say are handled directly by the game engine’s simple parser.
• IronPython scripts manage the complex, programmable aspects of the game such as NPC behaviors, game logic, and event triggers.

This approach provides the best of both worlds: a simple interface for players and a robust, dynamic scripting environment for game developers.