evennia/docs/sphinx/source/wiki/Scripts.rst

Scripts
=======

*Scripts* are the out-of-character siblings to the in-character
`Objects <Objects.html>`_. The name "Script" might suggest that they can
only be used to script the game but this is only part of their
usefulness (in the end we had to pick a single name for them). Scripts
are full Typeclassed database entities, just like Objects - with all the
advantages this entails. Likewise they can also store arbitrary
*Attributes*.

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.
-  They can work as timers and tickers - anything that may change with
   Time. But they can also have no time dependence at all.
-  They can describe State changes.
-  They can act as data stores for storing game data persistently in the
   database
-  They can be used to shared data between groups of objects

The most obvious use of Scripts may be to use them as *timers* or
*Events*. Consider a script running on the object ``Grandfather Clock``.
The script has a timer that tells it to fire every hour. This allows the
clock to chime regularly. The script might even regulate how often the
clock must be rewound so it won't stop.

Scripts may act as changeable *States*. Consider for example creating a
'dark' room. It has two scripts assigned on it - one ``DarkState``
script, and one ``BrightState`` script. When characters enter the dark
room, it assigns a custom `Cmdset <Commands.html>`_ to them. This
command set defines the parameters of the state they describe. In this
case it limits their actions because of the darkness. After the
characters have stumbled around for a while, someone brings up a torch.
As a light source is now in the room, ``DarkState`` reacts to this by
shutting down itself and handing over control to the ``BrightState``
script that restores normal commands. Finally, when the character with
the torch leaves the room, the ``BrightState`` script detects this and
obediently hands control back to the ``DarkState``, leaving the
remaining poor characters in darkness once again.

By combining state-changes with timers one can make a room look
different during nighttime than it does during the day. Weather and
seasons might come and go. But one can also achieve more complex things
such as state-AI systems that make mobs move around and possibly pursue
characters between rooms.

Scripts are also excellent places to store game data in an OOC way. A
groupd of objects may share date by use of a Script object they all hold
references to.

In short, Scripts can be used for a lot of things.

How to create your own Script types
-----------------------------------

An Evennia Script is, per definition, a Python class that includes
``src.scripts.scripts.Script`` among its parents (if you are aware of
how typeclasses work, this is a typeclass linked to the ``ScriptDB``
database model). Scripts have no in-game representation and you cannot
define them with any default commands. They have to be created in python
code modules and imported from there into the game.

Scripts may run directly 'on' `Objects <Objects.html>`_, affecting that
object and maybe its surroundings or contents. An alternative way to
affect many objects (rather than one script per object) is to create one
Script and have it call all objects that "subscribe" to it at regular
intervals (a *ticker*). Scripts not defined directly 'on' objects are
called *Global* scripts.

Custom script modules are usually stored in ``game/gamesrc/scripts``. As
a convenience you can inherit sripts from ``ev.Script``.

You can try out scripts an add them to objects by use of the ``@script``
command (not to the confused with ``@scripts`` which lists scripts). You
can try it out with an example script:

::

     > @script self = examples.bodyfunctions.BodyFunctions

This should cause some random messages. The ``/stop`` switch will kill
the script again.

In code, if you add scripts to `Objects <Objects.html>`_ the script can
then manipulate the object as desired. The script is added to the
object's *script handler*, called simply ``scripts``. The handler takes
care of all initialization and startup of the script for you.

::

     # adding a script to an existing object 'myobj'
     myobj.scripts.add("game.gamesrc.scripts.myscripts.CoolScript")
     # alternative way
     from src.utils.create import create_script
     create_script("game.gamesrc.scripts.myscripts.CoolScript", obj=myobj)

The creation method(s) takes an optional argument *key* that allows you
to name your script uniquely before adding it. This can be useful if you
add many scripts of the same type and later plan to use
``myobj.scripts.delete`` to remove individual scripts.

You can create global scripts with
``ev.create_script (a shortcut to ``\ src.utils.create.create\_script()\ ``). Just don't supply an object to store it on. {{{  # adding a global script  from ev import create_script  create_script("game.gamesrc.scripts.globals.MyGlobalEconomy", key="economy", obj=None) }}} Assuming the Script ``\ game.gamesrc.scripts.globals.MyGlobalEconomy\ `` exists, this will create and start it as a global script.  == Properties and functions defined on Scripts ==  It's important to know the variables controlling the script before one can create one.  Beyond those properties assigned to all typeclassed objects (see [Typeclasses]), such as ``\ key\ ``, ``\ db\ ``, ``\ ndb\ `` etc, all Scripts also have the following properties:    * ``\ desc\ `` - an optional description of the script's function. Seen in script listings.   * ``\ interval\ `` - how often the script should run. If ``\ interval
==
0\ `` (default), it runs forever, without any repeating (it will not accept a negative value).  * ``\ 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.  * ``\ persistent\ ``- if this script should survive a server reboot.  There is one special property:   * ``\ obj\ `` - the [Objects 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 also Evennia calls 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 first starts. 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 on a full systems shutdown.   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. No hooks are called - as far as the script knows, it never stopped - this is a suspension of the script, not a change of state.  * ``\ unpause()\ `` - resumes a previously paused script. Timers etc are restored to what they were before pause. The server unpauses all paused scripts after a server reload. No hooks are called - as far as the script is concerned, it never stopped running.  * ``\ time\_until\_next\_repeat()\ `` - for timed scripts, this returns the time in seconds until it next fires. Returns ``\ None\ `` if ``\ interval==0\ ``.   == Example script ==  {{{ import random from ev import Script class Weather(Script):      "Displays weather info. Meant to be attached to a room."     def at_script_creation(self):         "Called once, during initial creation"         self.key = "weather_script"         self.desc = "Gives random weather messages."         self.interval = 60 * 5 # every 5 minutes         self.persistent = True     self.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 
command:

::

     @script here = weather.Weather