Coding Utils

Evennia comes with many utilities to help with common coding tasks. Most are accessible directly from the flat API, otherwise you can find them in the evennia/utils/ folder.

Searching

A common thing to do is to search for objects. The most common time one needs to do this is inside a command body. There it’s easiest to use the search method defined on all objects. This will search for objects in the same location and inside the caller:

obj = self.caller.search(objname)

Give the keyword global_search=True to extend search to encompass entire database. Also aliases with be matched by this search. You will find multiple examples of this functionality in the default command set.

If you need to search for objects in a code module you can use the functions in evennia.utils.search. You can access these as shortcuts evennia.search_*.

from evennia import search_object
obj = search_object(objname)

Note that these latter methods will always return a list of results, even if the list has one or zero entries.

Create

Apart from the in-game build commands (@create etc), you can also build all of Evennia’s game entities directly in code (for example when defining new create commands).

import evennia
#
myobj = evennia.create_objects("game.gamesrc.objects.myobj.MyObj",
                               key="MyObj")
myscr = evennia.create_script("game.gamesrc.scripts.myscripts.MyScript",
                              obj=myobj)
helpentry = evennia.create_help_entry("Emoting", "Emoting means that ...")
msg = evennia.create_message(senderobj, [receiverobj], "Hello ...")
channel = evennia.create_channel("news")
player = evennia.create_player("Henry", "henry@test.com", "H@passwd")

Each of these create-functions have a host of arguments to further customize the created entity. See evennia/utils/create.py for more information.

Logging

Normally you can use Python print statements to see output to the terminal/log. The print statement should only be used for debugging though. For producion output, use the logger which will create proper logs either to terminal or to file.

from evennia import logger
#
logger.log_err("This is an Error!")
logger.log_warn("This is a Warning!")
logger.log_info("This is normal information")
logger.log_dep("This feature is deprecated")

There is a special log-message type, log_trace() that is intended to be called from inside a traceback - this can be very useful for relaying the traceback message back to log without having it kill the server.

try:
  # [some code that may fail...]
except Exception:
  logger.log_trace("This text will show beneath the traceback itself.")

The log_file logger, finally, is a very useful logger for outputting arbitrary log messages. This is a heavily optimized asynchronous log mechanism using threads to avoid overhead. You should be able to use it for very heavy custom logging without fearing disk-write delays.

logger.log_file(message, filename="mylog.log")

If not an absolute path is given, the log file will appear in the mygame/server/logs/ directory. If the file already exists, it will be appended to. Timestamps on the same format as the normal Evennia logs will be automatically added to each entry. If a filename is not specified, output will be written to a file game/logs/game.log.

Game time

Evennia tracks the current server time. You can access this time via the evennia.gametime shortcut:

from evennia import gametime

# all the functions below return times in seconds).

# total running time of the server
runtime = gametime.runtime()
# time since latest hard reboot (not including reloads)
uptime = gametime.uptime()
# server epoch (its start time)
server_epoch = gametime.server_epoch()

# in-game epoch (this can be set by `settings.TIME_GAME_EPOCH`.
# If not, the server epoch is used.
game_epoch = gametime.game_epoch()
# in-game time passed since time started running
gametime = gametime.gametime()
# in-game time plus game epoch (i.e. the current in-game
# time stamp)
gametime = gametime.gametime(absolute=True)
# reset the game time (back to game epoch)
gametime.reset_gametime()

The setting TIME_FACTOR determines how fast/slow in-game time runs compared to the real world. The setting TIME_GAME_EPOCH sets the starting game epoch (in seconds). The functions from the gametime module all return their times in seconds. You can convert this to whatever units of time you desire for your game. You can use the @time command to view the server time info.

You can also schedule things to happen at specific in-game times using the gametime.schedule function:

import evennia

def church_clock:
    limbo = evennia.search_object(key="Limbo")
    limbo.msg_contents("The church clock chimes two.")

gametime.schedule(church_clock, hour=2)

utils.time_format()

This function takes a number of seconds as input (e.g. from the gametime module above) and converts it to a nice text output in days, hours etc. It’s useful when you want to show how old something is. It converts to four different styles of output using the style keyword:

  • style 0 - 5d:45m:12s (standard colon output)
  • style 1 - 5d (shows only the longest time unit)
  • style 2 - 5 days, 45 minutes (full format, ignores seconds)
  • style 3 - 5 days, 45 minutes, 12 seconds (full format, with seconds)

utils.inherits_from()

This useful function takes two arguments - an object to check and a parent. It returns True if object inherits from parent at any distance (as opposed to Python’s in-built is_instance() that will only catch immediate dependence). This function also accepts as input any combination of classes, instances or python-paths-to-classes.

Note that Python code should usually work with duck typing. But in Evennia’s case it can sometimes be useful to check if an object inherits from a given Typeclass as a way of identification. Say for example that we have a typeclass Animal. This has a subclass Felines which in turn has a subclass HouseCat. Maybe there are a bunch of other animal types too, like horses and dogs. Using inherits_from will allow you to check for all animals in one go:

from evennia import utils
if (utils.inherits_from(obj, "typeclasses.objects.animals.Animal"):
   obj.msg("The bouncer stops you in the door. He says: 'No talking animals allowed.'")

utils.delay()

This is a thin wrapper around a Twisted construct called a deferred. It simply won’t return until a given number of seconds have passed, at which time it will trigger a given callback with whatever argument. This is a small and lightweight (non-persistent) alternative to a full Scripts. Contrary to a Script it can also handle sub-second timing precision (although this is not something you should normally need to worry about).

Some text utilities

In a text game, you are naturally doing a lot of work shuffling text back and forth. Here is a non-complete selection of text utilities found in evennia/utils/utils.py (shortcut evennia.utils). If nothing else it can be good to look here before starting to develop a solution of your own.

utils.fill()

This flood-fills a text to a given width (shuffles the words to make each line evenly wide). It also indents as needed.

outtxt = fill(intxt, width=78, indent=4)

utils.crop()

This function will crop a very long line, adding a suffix to show the line actually continues. This can be useful in listings when showing multiple lines would mess up things.

intxt = "This is a long text that we want to crop."
outtxt = crop(intxt, width=19, suffix="[...]")
# outtxt is now "This is a long text[...]"

utils.dedent()

This solves what may at first glance appear to be a trivial problem with text - removing indentations. It is used to shift entire paragraphs to the left, without disturbing any further formatting they may have. A common case for this is when using Python triple-quoted strings in code - they will retain whichever indentation they have in the code, and to make easily-readable source code one usually don’t want to shift the string to the left edge.

#python code is entered at a given indentation
      intxt = """
      This is an example text that will end
      up with a lot of whitespace on the left.
                It also has indentations of
                its own."""
      outtxt = dedent(intxt)
      # outtxt will now retain all internal indentation
      # but be shifted all the way to the left.

Normally you do the dedent in the display code (this is for example how the help system homogenizes help entries).

text conversion()

Evennia supplies two utility functions for converting text to the correct encodings. to_str() and to_unicode(). The difference from Python’s in-built str() and unicode() operators are that the Evennia ones makes use of the ENCODINGS setting and will try very hard to never raise a traceback but instead echo errors through logging. See here for more info.

Making ascii tables

The EvTable class (evennia/utils/evtable.py) can be used to create correctly formatted text tables. There is also EvForm (evennia/utils/evform.py). This reads a fixed-format text template from a file in order to create any level of sophisticated ascii layout. Both evtable and evform have lots of options and inputs so see the header of each module for help.

The third-party PrettyTable module is also included in Evennia. PrettyTable is considered deprecated in favor of EvTable since PrettyTable cannot handle ANSI colour. PrettyTable can be found in evennia/utils/prettytable/. See its homepage above for instructions.