Tutorial for basic MUSH like game¶
This tutorial lets you code a small but complete and functioning MUSH-like game in Evennia. A MUSH is, for our purposes, a class of roleplay-centric games focused on free form storytelling. Even if you are not interested in MUSH:es, this is still a good first game-type to try since it’s not so code heavy. You will be able to use the same principles for building other types of games.
The tutorial starts from scratch. If you did the First Steps Coding tutorial already you should have some ideas about how to do some of the steps already.
The following are the (very simplistic and cut-down) features we will implement (this was taken from a feature request from a MUSH user new to Evennia). A Character in this system should:
- Have a “Power” score from 1 to 10 that measures how strong they are (stand-in for the stat system).
- Have a command (e.g.
+setpower 4) that sets their power (stand-in for character generation code).
- Have a command (e.g.
+attack) that lets them roll their power and produce a “Combat Score” between
10*Power, displaying the result and editing their object to record this number (stand-in for
+actionsin the command code).
- Have a command that displays everyone in the room and what their most recent “Combat Score” roll was (stand-in for the combat code).
- Have a command (e.g.
+createNPC Jenkins) that creates an NPC with full abilities.
- Have a command to control NPCs, such as
+npc/cmd (name)=(command)(stand-in for the NPC controlling code).
In this tutorial we will assume you are starting from an empty database without any previous modifications.
To emulate a MUSH, the default
MULTISESSION_MODE=0 is enough (one
unique session per player/character). This is the default so you don’t
need to change anything. You will still be able to puppet/unpuppet
objects you have permission to, but there is no character selection out
of the box in this mode.
We will assume our game folder is called
mygame henceforth. You
should be fine with the default SQLite3 database.
Creating the Character¶
First thing is to choose how our Character class works. We don’t need to define a special NPC object – an NPC is after all just a Character without a Player currently controlling them.
Make your changes in the
# mygame/typeclasses/characters.py from evennia import DefaultCharacter class Character(DefaultCharacter): """ [...] """ def at_object_creation(self): "This is called when object is first created, only." self.db.power = 1 self.db.combat_score = 1
We defined two new Attributes
combat_score and set
them to default values. Make sure to
@reload the server if you had
it already running (you need to reload every time you update your python
code, don’t worry, no players will be disconnected by the reload).
Note that only new characters will see your new Attributes (since the
at_object_creation hook is called when the object is first created,
existing Characters won’t have it). To update yourself, run
This resets your own typeclass (the
/force switch is a safety
measure to not do this accidentally), this means that
at_object_creation is re-run.
Under the “Persistent attributes” heading you should now find the new
score set on yourself by
at_object_creation. If you don’t, first make sure you
@reloaded into the new code, next look at your server log (in the
terminal/console) to see if there were any syntax errors in your code
that may have stopped your new code from loading correctly.
We assume in this example that Players first connect into a “character generation area”. Evennia also supports full OOC menu-driven character generation, but for this example, a simple start room is enough. When in this room (or rooms) we allow character generation commands. In fact, character generation commands will only be available in such rooms.
Note that this again is made so as to be easy to expand to a
full-fledged game. With our simple example, we could simply set an
is_in_chargen flag on the player and have the
check it. Using this method however will make it easy to add more
What we need are the following:
- One character generation Command to set the “Power” on the
- A chargen CmdSet to hold this command. Lets call it
- A custom
ChargenRoomtype that makes this set of commands available to players in such rooms.
- One such room to test things in.
The +setpower command¶
For this tutorial we will add all our new commands to
mygame/commands/command.py but you could split your commands into
multiple module if you prefered.
For this tutorial character generation will only consist of one Command to set the Character s “power” stat. It will be called on the following MUSH-like form:
command.py file. It contains documented empty templates for the
base command and the “MuxCommand” type used by default in Evennia. We
will use the plain
Command type here, the
offers some extra features like stripping whitespace that may be useful
- if so, just import from that instead.
Add the following to the end of the
# end of command.py from evennia import Command # just for clarity; already imported above class CmdSetPower(Command): """ set the power of a character Usage: +setpower <1-10> This sets the power of the current character. This can only be used during character generation. """ key = "+setpower" help_category = "mush" def func(self): "This performs the actual command" errmsg = "You must supply a number between 1 and 10." if not self.args: self.caller.msg(errmsg) return try: power = int(self.args) except ValueError: self.caller.msg(errmsg) return if not (1 <= power <= 10): self.caller.msg(errmsg) return # at this point the argument is tested as valid. Let's set it. self.caller.db.power = power self.caller.msg("Your Power was set to %i." % power)
This is a pretty straightforward command. We do some error checking,
then set the power on ourself. We use a
help_category of “mush” for
all our commands, just so they are easy to find and separate in the help
Save the file. We will now add it to a new CmdSet so it can be accessed (in a full chargen system you would of course have more than one command here).
mygame/commands/default_cmdsets.py and import your
command.py module at the top. We also import the default
class for the next step:
from evennia import CmdSet from commands import command
Next scroll down and define a new command set (based on the base
CmdSet class we just imported at the end of this file, to hold only
our chargen-specific command(s):
# end of default_cmdsets.py class ChargenCmdset(CmdSet): """ This cmdset it used in character generation areas. """ key = "Chargen" def at_cmdset_creation(self): "This is called at initialization" self.add(command.CmdSetPower())
In the future you can add any number of commands to this cmdset, to expand your character generation system as you desire. Now we need to actually put that cmdset on something so it’s made available to users. We could put it directly on the Character, but that would make it available all the time. It’s cleaner to put it on a room, so it’s only available when players are in that room.
We will create a simple Room typeclass to act as a template for all our
Chargen areas. Edit
# end of rooms.py from commands.default_cmdsets import ChargenCmdset class ChargenRoom(Room): """ This room class is used by character-generation rooms. It makes the ChargenCmdset available. """ def at_object_creation(self): "this is called only at first creation" self.cmdset.add(ChargenCmdset, permanent=True)
Note how new rooms created with this typeclass will always start with
ChargenCmdset on themselves. Don’t forget the
keyword or you will loose the cmdset after a server reload. For more
information about Command Sets and Commands, see the respective
First, make sure you have
@reloaded the server (or use
evennia reload from the terminal) to have your new python code added
to the game. Check your terminal and fix any errors you see - the error
traceback lists exactly where the error is found - look line numbers in
files you have changed.
We can’t test things unless we have some chargen areas to test. Log into the game (you should at this point be using the new, custom Character class). Let’s dig a chargen area to test.
@dig chargen:rooms.ChargenRoom = chargen,finish
If you read the help for
@dig you will find that this will create a
new room named
chargen. The part after the
: is the python-path
to the Typeclass you want to use. Since Evennia will automatically try
typeclasses folder of our game directory, we just specify
rooms.ChargenRoom, meaning it will look inside the module
rooms.py for a class named
ChargenRoom (which is what we created
above). The names given after
= are the names of exits to and from
the room from your current location. You could also append aliases to
each one name, such as
chargento it and an exit back here named
finish. If you see errors at this stage, you must fix them in your code.
This should bring you to the chargen room. Being in there you should now
+setpower command available, so test it out. When you leave
finish exit), the command will go away and trying
+setpower should now give you a command-not-found error. Use
ex me (as a privileged user) to check so the
has been set correctly.
If things are not working, make sure your typeclasses and commands are free of bugs and that you have entered the paths to the various command sets and commands correctly. Check the logs or command line for tracebacks and errors.
We will add our combat command to the default command set, meaning it
will be available to everyone at all times. The combat system consists
+attack command to get how successful our attack is. We also
change the default
look command to display the current combat score.
Attacking with the +attack command¶
Attacking in this simple system means rolling a random “combat score”
influenced by the
power stat set during Character generation:
> +attack You +attack with a combat score of 12!
Go back to
mygame/commands/command.py and add the command to the end
import random class CmdAttack(Command): """ issues an attack Usage: +attack This will calculate a new combat score based on your Power. Your combat score is visible to everyone in the same location. """ key = "+attack" help_category = "mush" def func(self): "Calculate the random score between 1-10*Power" caller = self.caller power = caller.db.power if not power: # this can happen if caller is not of # our custom Character typeclass power = 1 combat_score = random.randint(1, 10 * power) caller.db.combat_score = combat_score # announce message = "%s +attack%s with a combat score of %s!" caller.msg(message % ("You", "", combat_score)) caller.location.msg_contents(message % (caller.key, "s", combat_score), exclude=caller)
What we do here is simply to generate a “combat score” using Python’s
random.randint() function. We then store that and echo the
result to everyone involved.
To make the
+attack command available to you in game, go back to
mygame/commands/default_cmdsets.py and scroll down to the
CharacterCmdSet class. At the correct place add this line:
@reload Evennia and the
+attack command should be available to
you. Run it and use e.g.
@ex to make sure the
attribute is saved correctly.
Have “look” show combat scores¶
Players should be able to view all current combat scores in the room. We
could do this by simply adding a second command named something like
+combatscores, but we will instead let the default
do the heavy lifting for us and display our scores as part of its normal
output, like this:
> look Tom Tom (combat score: 3) This is a great warrior.
We don’t actually have to modify the
look command itself however. To
understand why, take a look at how the default
look is actually
defined. It sits in
evennia/commands/default/general.py (or browse
it online here). You will find that the actual return text is done by
look command calling a hook method named
on the object looked at. All the
look does is to echo whatever this
hook returns. So what we need to do is to edit our custom Character
typeclass and overload its
return_appearance to return what we want
(this is where the advantage of having a custom typeclass comes into
play for real).
Go back to your custom Character typeclass in
mygame/typeclasses/characters.py. The default implementation of
return appearance is found in
If you want to make bigger changes you could copy & paste the whole
default thing into our overloading method. In our case the change is
class Character(DefaultCharacter): """ [...] """ def at_object_creation(self): "This is called when object is first created, only." self.db.power = 1 self.db.combat_score = 1 def return_appearance(self, looker): """ The return from this method is what looker sees when looking at this object. """ text = super(Character, self).return_appearance(looker) cscore = " (combat score: %s)" % self.db.combat_score if "\n" in text: # text is multi-line, add score after first line first_line, rest = text.split("\n", 1) text = first_line + cscore + "\n" + rest else: # text is only one line; add score to end text += cscore return text
What we do is to simply let the default
return_appearance do its
super will call the parent’s version of the same method). We
then split out the first line of this text, append our
and put it back together again.
@reload the server and you should be able to look at other
Characters and see their current combat scores.
Note: A potentially more useful way to do this would be to overload the entire
Rooms of your mush and change how they list their contents; in that way one could see all combat scores of all present Characters at the same time as looking at the room. We leave this as an exercise.
Here we will re-use the Character class by introducing a command that can create NPC objects. We should also be able to set its Power and order it around.
There are a few ways to define the NPC class. We could in theory create a custom typeclass for it and put a custom NPC-specific cmdset on all NPCs. This cmdset could hold all manipulation commands. Since we expect NPC manipulation to be a common occurrence among the user base however, we will instead put all relevant NPC commands in the default command set and limit eventual access with Permissions and Locks.
Creating an NPC with +createNPC¶
We need a command for creating the NPC, this is a very straightforward command:
> +createnpc Anna You created the NPC 'Anna'.
At the end of
command.py, create our new command:
from evennia import create_object class CmdCreateNPC(Command): """ create a new npc Usage: +createNPC <name> Creates a new, named NPC. The NPC will start with a Power of 1. """ key = "+createnpc" aliases = ["+createNPC"] locks = "call:not perm(nonpcs)" help_category = "mush" def func(self): "creates the object and names it" caller = self.caller if not self.args: caller.msg("Usage: +createNPC <name>") return if not caller.location: # may not create npc when OOC caller.msg("You must have a location to create an npc.") return # make name always start with capital letter name = self.args.strip().capitalize() # create npc in caller's location npc = create_object("characters.Character", key=name, location=caller.location, locks="edit:id(%i) and perm(Builders);call:false()" % caller.id) # announce message = "%s created the NPC '%s'." caller.msg(message % ("You", name)) caller.location.msg_contents(message % (caller.key, name), exclude=caller)
Here we define a
+createNPC works too) that is
callable by everyone not having the
nonpcs “permission” (in
Evennia, a “permission” can just as well be used to block access, it
depends on the lock we define). We create the NPC object in the caller’s
current location, using our custom
Character typeclass to do so.
We set an extra lock condition on the NPC, which we will use to check who may edit the NPC later – we allow the creator to do so, and anyone with the Builders permission (or higher). See Locks for more information about the lock system.
Note that we just give the object default permissions (by not specifying
permissions keyword to the
create_object() call). In some
games one might want to give the NPC the same permissions as the
Character creating them, this might be a security risk though.
Add this command to your default cmdset the same way you did the
+attack command earlier.
@reload and it will be available to
Editing the NPC with +editNPC¶
Since we re-used our custom character typeclass, our new NPC already has a Power value - it defaults to 1. How do we change this?
There are a few ways we can do this. The easiest is to remember that the
power attribute is just a simple Attribute stored on the NPC
object. So as a Builder or Admin we could set this right away with the
@set mynpc/power = 6
@set command is too generally powerful though, and thus only
available to staff. We will add a custom command that only changes the
things we want players to be allowed to change. We could in principle
re-work our old
+setpower command, but let’s try something more
useful. Let’s make a
> +editNPC Anna/power = 10 Set Anna's property 'power' to 10.
This is a slightly more complex command. It goes at the end of your
command.py file as before.
class CmdEditNPC(Command): """ edit an existing NPC Usage: +editnpc <name>[/<attribute> [= value]] Examples: +editnpc mynpc/power = 5 +editnpc mynpc/power - displays power value +editnpc mynpc - shows all editable attributes and values This command edits an existing NPC. You must have permission to edit the NPC to use this. """ key = "+editnpc" aliases = ["+editNPC"] locks = "cmd:not perm(nonpcs)" help_category = "mush" def parse(self): "We need to do some parsing here" args = self.args propname, propval = None, None if "=" in args: args, propval = [part.strip() for part in args.rsplit("=", 1)] if "/" in args: args, propname = [part.strip() for part in args.rsplit("/", 1)] # store, so we can access it below in func() self.name = args self.propname = propname # a propval without a propname is meaningless self.propval = propval if propname else None def func(self): "do the editing" allowed_propnames = ("power", "attribute1", "attribute2") caller = self.caller if not self.args or not self.name: caller.msg("Usage: +editnpc name[/propname][=propval]") return npc = caller.search(self.name) if not npc: return if not npc.access(caller, "edit"): caller.msg("You cannot change this NPC.") return if not self.propname: # this means we just list the values output = "Properties of %s:" % npc.key for propname in allowed_propnames: propvalue = npc.attributes.get(propname, default="N/A") output += "\n %s = %s" % (propname, propvalue) caller.msg(output) elif self.propname not in allowed_propnames: caller.msg("You may only change %s." % ", ".join(allowed_propnames)) elif self.propval: # assigning a new propvalue # in this example, the properties are all integers... intpropval = int(self.propval) npc.attributes.add(self.propname, intpropval) caller.msg("Set %s's property '%s' to %s" % (npc.key, self.propname, self.propval)) else: # propname set, but not propval - show current value caller.msg("%s has property %s = %s" % (npc.key, self.propname, npc.attributes.get(self.propname, default="N/A")))
This command example shows off the use of more advanced parsing but otherwise it’s mostly error checking. It searches for the given npc in the same room, and checks so the caller actually has permission to “edit” it before continuing. A player without the proper permission won’t even be able to view the properties on the given NPC. It’s up to each game if this is the way it should be.
Add this to the default command set like before and you should be able to try it out.
Note: If you wanted a player to use this command to change an on-object property like the NPC’s name (the ``key`` property), you’d need to modify the command since “key” is not an Attribute (it is not retrievable via ``npc.attributes.get`` but directly via ``npc.key``). We leave this as an optional exercise.
Making the NPC do stuff - the +npc command¶
Finally, we will make a command to order our NPC around. For now, we will limit this command to only be usable by those having the “edit” permission on the NPC. This can be changed if it’s possible for anyone to use the NPC.
The NPC, since it inherited our Character typeclass has access to most
commands a player does. What it doesn’t have access to are Session and
Player-based cmdsets (which means, among other things that they cannot
chat on channels, but they could do that if you just added those
commands). This makes the
+npc command simple:
+npc Anna = say Hello! Anna says, 'Hello!'
Again, add to the end of your
class CmdNPC(Command): """ controls an NPC Usage: +npc <name> = <command> This causes the npc to perform a command as itself. It will do so with its own permissions and accesses. """ key = "+npc" locks = "call:not perm(nonpcs)" help_category = "mush" def parse(self): "Simple split of the = sign" name, cmdname = None, None if "=" in self.args: name, cmdname = [part.strip() for part in self.args.rsplit("=", 1)] self.name, self.cmdname = name, cmdname def func(self): "Run the command" caller = self.caller if not self.cmdname: caller.msg("Usage: +npc <name> = <command>") return npc = caller.search(self.name) if not npc: return if not npc.access(caller, "edit"): caller.msg("You may not order this NPC to do anything.") return # send the command order npc.execute_cmd(self.cmdname) caller.msg("You told %s to do '%s'." % (npc.key, self.cmdname))
Note that if you give an erroneous command, you will not see any error
message, since that error will be returned to the npc object, not to
you. If you want players to see this, you can give the caller’s session
ID to the
execute_cmd call, like this:
Another thing to remember is however that this is a very simplistic way
to control NPCs. Evennia supports full puppeting very easily. A Player
(assuming the “puppet” permission was set correctly) could simply do
@ic mynpc and be able to play the game “as” that NPC. This is in
fact just what happens when a Player takes control of their normal
Character as well.
This ends the tutorial. It looks like a lot of text but the amount of code you have to write is actually relatively short. At this point you should have a basic skeleton of a game and a feel for what is involved in coding your game.
From here on you could build a few more ChargenRooms and link that to a
bigger grid. The
+setpower command can either be built upon or
accompanied by many more to get a more elaborate character generation.
The simple “Power” game mechanic should be easily expandable to
something more full-fledged and useful, same is true for the combat
score principle. The
+attack could be made to target a specific
player (or npc) and automatically compare their relevant attributes to
determine a result.