Scripts

Scripts are the out-of-character siblings to the in-character Objects. Scripts are so flexible that the “Script” is a bit limiting

  • we had to pick something to name them after all. Other possible names (depending on what you’d use them for) would be OOBObjects, StorageContainers or TimerObjects.

Scripts can be used for many different things in Evennia:

  • They can attach to Objects to influence them in various ways - or exist independently of any one in-game entity (so-called Global Scripts).

  • They can work as timers and tickers - anything that may change with Time. But they can also have no time dependence at all. Note though that if all you want is just to have an object method called repeatedly, you should consider using the TickerHandler which is more limited but is specialized on just this task.

  • They can describe State changes. A Script is an excellent platform for hosting a persistent, but unique system handler. For example, a Script could be used as the base to track the state of a turn-based combat system. Since Scripts can also operate on a timer they can also update themselves regularly to perform various actions.

  • They can act as data stores for storing game data persistently in the database (thanks to its ability to have Attributes).

  • They can be used as OOC stores for sharing data between groups of objects, for example for tracking the turns in a turn-based combat system or barter exchange.

Scripts are Typeclassed entities and are manipulated in a similar way to how it works for other such Evennia entities:

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# create a new script
new_script = evennia.create_script(key="myscript", typeclass=...)

# search (this is always a list, also if there is only one match)
list_of_myscript = evennia.search_script("myscript")

Defining new Scripts

A Script is defined as a class and is created in the same way as other typeclassed entities. The class has several properties to control the timer-component of the scripts. These are all optional - leaving them out will just create a Script with no timer components (useful to act as a database store or to hold a persistent game system, for example).

This you can do for example in the module evennia/typeclasses/scripts.py. Below is an example Script Typeclass.

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from evennia import DefaultScript

class MyScript(DefaultScript):

    def at_script_creation(self):
        self.key = "myscript"
        self.interval = 60  # 1 min repeat

    def at_repeat(self):
        # do stuff every minute

In mygame/typeclasses/scripts.py is the Script class which inherits from DefaultScript already. This is provided as your own base class to do with what you like: You can tweak Script if you want to change the default behavior and it is usually convenient to inherit from this instead. Here’s an example:

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    # for example in mygame/typeclasses/scripts.py
    # Script class is defined at the top of this module

    import random

    class Weather(Script):
        """
        A timer script that displays weather info. Meant to
        be attached to a room.
          
        """
        def at_script_creation(self):
            self.key = "weather_script"
            self.desc = "Gives random weather messages."
            self.interval = 60 * 5  # every 5 minutes
            self.persistent = True  # will survive reload

        def at_repeat(self):
            "called every self.interval seconds."
            rand = random.random()
            if rand < 0.5:
                weather = "A faint breeze is felt."
            elif rand < 0.7:
                weather = "Clouds sweep across the sky."
            else:
                weather = "There is a light drizzle of rain."
            # send this message to everyone inside the object this
            # script is attached to (likely a room)
            self.obj.msg_contents(weather)

If we put this script on a room, it will randomly report some weather to everyone in the room every 5 minutes.

To activate it, just add it to the script handler (scripts) on an Room. That object becomes self.obj in the example above. Here we put it on a room called myroom:

    myroom.scripts.add(scripts.Weather)

Note that typeclasses in your game dir is added to the setting TYPECLASS_PATHS. Therefore we don’t need to give the full path (typeclasses.scripts.Weather but only scripts.Weather above.

If you wanted to stop and delete that script on the Room. You could do that with the script handler by passing the delete method with the script key (self.key) as:

    myroom.scripts.delete('weather_script')

Note that If no key is given, this will delete all scripts on the object!

You can also create scripts using the evennia.create_script function:

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    from evennia import create_script
    create_script('typeclasses.weather.Weather', obj=myroom)

Note that if you were to give a keyword argument to create_script, that would override the default value in your Typeclass. So for example, here is an instance of the weather script that runs every 10 minutes instead (and also not survive a server reload):

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    create_script('typeclasses.weather.Weather', obj=myroom,
                   persistent=False, interval=10*60)

From in-game you can use the @script command to launch the Script on things:

     @script here = typeclasses.scripts.Weather

You can conveniently view and kill running Scripts by using the @scripts command in-game.

Properties and functions defined on Scripts

A Script has all the properties of a typeclassed object, such as db and ndb(see Typeclasses). Setting key is useful in order to manage scripts (delete them by name etc). These are usually set up in the Script’s typeclass, but can also be assigned on the fly as keyword arguments to evennia.create_script.

  • desc - an optional description of the script’s function. Seen in script listings.

  • interval - how often the script should run. If interval == 0 (default), this script has no timing component, will not repeat and will exist forever. This is useful for Scripts used for storage or acting as bases for various non-time dependent game systems.

  • start_delay - (bool), if we should wait interval seconds before firing for the first time or not.

  • repeats - How many times we should repeat, assuming interval > 0. If repeats is set to <= 0, the script will repeat indefinitely. Note that each firing of the script (including the first one) counts towards this value. So a Script with start_delay=False and repeats=1 will start, immediately fire and shut down right away.

  • persistent- if this script should survive a server reset or server shutdown. (You don’t need to set this for it to survive a normal reload - the script will be paused and seamlessly restart after the reload is complete).

There is one special property:

  • obj - the Object this script is attached to (if any). You should not need to set this manually. If you add the script to the Object with myobj.scripts.add(myscriptpath) or give myobj as an argument to the utils.create.create_script function, the obj property will be set to myobj for you.

It’s also imperative to know the hook functions. Normally, overriding these are all the customization you’ll need to do in Scripts. You can find longer descriptions of these in src/scripts/scripts.py.

  • at_script_creation() - this is usually where the script class sets things like interval and repeats; things that control how the script runs. It is only called once - when the script is first created.

  • is_valid() - determines if the script should still be running or not. This is called when running obj.scripts.validate(), which you can run manually, but which is also called by Evennia during certain situations such as reloads. This is also useful for using scripts as state managers. If the method returns False, the script is stopped and cleanly removed.

  • at_start() - this is called when the script starts or is unpaused. For persistent scripts this is at least once ever server startup. Note that this will always be called right away, also if start_delay is True.

  • at_repeat() - this is called every interval seconds, or not at all. It is called right away at startup, unless start_delay is True, in which case the system will wait interval seconds before calling.

  • at_stop() - this is called when the script stops for whatever reason. It’s a good place to do custom cleanup.

  • at_server_reload() - this is called whenever the server is warm-rebooted (e.g. with the @reload command). It’s a good place to save non-persistent data you might want to survive a reload.

  • at_server_shutdown() - this is called when a system reset or systems shutdown is invoked.

Running methods (usually called automatically by the engine, but possible to also invoke manually)

  • start() - this will start the script. This is called automatically whenever you add a new script to a handler. at_start() will be called.

  • stop() - this will stop the script and delete it. Removing a script from a handler will stop it automatically. at_stop() will be called.

  • pause() - this pauses a running script, rendering it inactive, but not deleting it. All properties are saved and timers can be resumed. This is called automatically when the server reloads and will not lead to the at_stop() hook being called. This is a suspension of the script, not a change of state.

  • unpause() - resumes a previously paused script. The at_start() hook will be called to allow it to reclaim its internal state. Timers etc are restored to what they were before pause. The server automatically unpauses all paused scripts after a server reload.

  • force_repeat() - this will forcibly step the script, regardless of when it would otherwise have fired. The timer will reset and the at_repeat() hook is called as normal. This also counts towards the total number of repeats, if limited.

  • time_until_next_repeat() - for timed scripts, this returns the time in seconds until it next fires. Returns None if interval==0.

  • remaining_repeats() - if the Script should run a limited amount of times, this tells us how many are currently left.

  • reset_callcount(value=0) - this allows you to reset the number of times the Script has fired. It only makes sense if repeats > 0.

  • restart(interval=None, repeats=None, start_delay=None) - this method allows you to restart the Script in-place with different run settings. If you do, the at_stop hook will be called and the Script brought to a halt, then the at_start hook will be called as the Script starts up with your (possibly changed) settings. Any keyword left at None means to not change the original setting.

Global Scripts

A script does not have to be connected to an in-game object. If not it is called a Global script. You can create global scripts by simply not supplying an object to store it on:

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     # adding a global script
     from evennia import create_script
     create_script("typeclasses.globals.MyGlobalEconomy",
                    key="economy", persistent=True, obj=None)

Henceforth you can then get it back by searching for its key or other identifier with evennia.search_script. In-game, the scripts command will show all scripts.

Evennia supplies a convenient “container” called GLOBAL_SCRIPTS that can offer an easy way to access global scripts. If you know the name (key) of the script you can get it like so:

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from evennia import GLOBAL_SCRIPTS

my_script = GLOBAL_SCRIPTS.my_script
# needed if there are spaces in name or name determined on the fly
another_script = GLOBAL_SCRIPTS.get("another script")
# get all global scripts (this returns a Queryset)
all_scripts = GLOBAL_SCRIPTS.all()
# you can operate directly on the script
GLOBAL_SCRIPTS.weather.db.current_weather = "Cloudy"

Note that global scripts appear as properties on GLOBAL_SCRIPTS based on their key. If you were to create two global scripts with the same key (even with different typeclasses), the GLOBAL_SCRIPTS container will only return one of them (which one depends on order in the database). Best is to organize your scripts so that this does not happen. Otherwise, use evennia.search_script to get exactly the script you want.

There are two ways to make a script appear as a property on GLOBAL_SCRIPTS. The first is to manually create a new global script with create_script as mentioned above. Often you want this to happen automatically when the server starts though. For this you add a python global dictionary named GLOBAL_SCRIPTS to your settings.py file. The settings.py fie is located in mygame/conf/settings.py:

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GLOBAL_SCRIPTS = {
    "my_script": {
        "typeclass": "typeclasses.scripts.Weather",
        "repeats": -1,
        "interval": 50,
        "desc": "Weather script",
        "persistent": True
    },
    "storagescript": {
        "typeclass": "typeclasses.scripts.Storage",
        "persistent": True
    },
    {
    "another_script": {
        "typeclass": "typeclasses.another_script.AnotherScript"
    }
}

Here the key (myscript and storagescript above) is required, all other fields are optional. If typeclass is not given, a script of type settings.BASE_SCRIPT_TYPECLASS is assumed. The keys related to timing and intervals are only needed if the script is timed.

Note: Provide the full path to the scripts module in GLOBAL_SCRIPTS. In the example with another_script, you can also create separate script modules that exist beyond scrypt.py for further organizational requirements if needed.

Evennia will use the information in settings.GLOBAL_SCRIPTS to automatically create and start these scripts when the server starts (unless they already exist, based on their key). You need to reload the server before the setting is read and new scripts become available. You can then find the key you gave as properties on evennia.GLOBAL_SCRIPTS (such as evennia.GLOBAL_SCRIPTS.storagescript).

Note: Make sure that your Script typeclass does not have any critical errors. If so, you’ll see errors in your log and your Script will temporarily fall back to being a DefaultScript type.

Moreover, a script defined this way is guaranteed to exist when you try to access it:

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from evennia import GLOBAL_SCRIPTS
# first stop the script
GLOBAL_SCRIPTS.storagescript.stop()
# running the `scripts` command now will show no storagescript
# but below now it's recreated again!
storage = GLOBAL_SCRIPTS.storagescript

That is, if the script is deleted, next time you get it from GLOBAL_SCRIPTS, it will use the information in settings to recreate it for you.

Note that if your goal with the Script is to store persistent data, you should set it as persistent=True, either in settings.GLOBAL_SCRIPTS or in the Scripts typeclass. Otherwise any data you wanted to store on it will be gone (since a new script of the same name is restarted instead).

Dealing with Errors

Errors inside an timed, executing script can sometimes be rather terse or point to parts of the execution mechanism that is hard to interpret. One way to make it easier to debug scripts is to import Evennia’s native logger and wrap your functions in a try/catch block. Evennia’s logger can show you where the traceback occurred in your script.

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from evennia.utils import logger

class Weather(DefaultScript):

    # [...]

    def at_repeat(self):
        
        try:
            # [...] code as above
        except Exception:
            # logs the error
            logger.log_trace()
    

Example of a timed script

In-game you can try out scripts using the @script command. In the evennia/contrib/tutorial_examples/bodyfunctions.py is a little example script that makes you do little ‘sounds’ at random intervals. Try the following to apply an example time-based script to your character.

> @script self = bodyfunctions.BodyFunctions

Note: Since evennia/contrib/tutorial_examples is in the default setting TYPECLASS_PATHS, we only need to specify the final part of the path, that is, bodyfunctions.BodyFunctions.

If you want to inflict your flatulence script on another person, place or thing, try something like the following:

> @py self.location.search('matt').scripts.add('bodyfunctions.BodyFunctions')

Here’s how you stop it on yourself.

> @script/stop self = bodyfunctions.BodyFunctions

This will kill the script again. You can use the @scripts command to list all active scripts in the game, if any (there are none by default).

For another example of a Script in use, check out the Turn Based Combat System tutorial.