EvMenu¶

Is your answer yes or no?
_________________________________________
[Y]es! - Answer yes.
[N]o! - Answer no.
[A]bort - Answer neither, and abort.

> Y
You chose yes!

Thanks for your answer. Goodbye!

EvMenu is used for generate branching multi-choice menus. Each menu ‘node’ can accepts specific options as input or free-form input. Depending what the player chooses, they are forwarded to different nodes in the menu.

The EvMenu utility class is located in evennia/utils/evmenu.py. It allows for easily adding interactive menus to the game; for example to implement Character creation, building commands or similar. Below is an example of offering NPC conversation choices:

This is how the example menu at the top of this page will look in code:

from evennia.utils import evmenu

def _handle_answer(caller, raw_input, **kwargs):
    answer = kwargs.get("answer")
    caller.msg(f"You chose {answer}!")
    return "end"  # name of next node

def node_question(caller, raw_input, **kwargs):
    text = "Is your answer yes or no?"
    options = (
        {"key": ("[Y]es!", "yes", "y"),
         "desc": Answer yes.",
         "goto": _handle_answer, {"answer": "yes"}},
        {"key": ("[N]o!", "no", "n"),
         "desc": "Answer no.",
         "goto": _handle_answer, {"answer": "no"}},
        {"key": ("[A]bort", "abort", "a"),
         "desc": "Answer neither, and abort.",
         "goto": "end"}
    )
    return text, options

def node_end(caller, raw_input, **kwargs):
    text "Thanks for your answer. Goodbye!"
    return text, None  # empty options ends the menu

evmenu.EvMenu(caller, {"start": node_question, "end": node_end})

Note the call to EvMenu at the end; this immediately creates the menu for the caller. It also assigns the two node-functions to menu node-names start and end, which is what the menu then uses to reference the nodes.

Each node of the menu is a function that returns the text and a list of dicts describing the choices you can make on that node.

Each option details what it should show (key/desc) as well as which node to go to (goto) next. The “goto” should be the name of the next node to go (if None, the same node will be rerun again).

Above, the Abort option gives the “end” node name just as a string whereas the yes/no options instead uses the callable _handle_answer but pass different arguments to it. _handle_answer then returns the name of the next node (this allows you to perform actions when making a choice before you move on to the next node the menu). Note that _handle_answer is not a node in the menu, it’s just a helper function.

When choosing ‘yes’ (or ‘no’) what happens here is that _handle_answer gets called and echoes your choice before directing to the “end” node, which exits the menu (since it doesn’t return any options).

You can also write menus using the EvMenu templating language. This allows you to use a text string to generate simpler menus with less boiler plate. Let’s create exactly the same menu using the templating language:

from evennia.utils import evmenu

def _handle_answer(caller, raw_input, **kwargs):
    answer = kwargs.get("answer")
    caller.msg(f"You chose {answer}!")
    return "end"  # name of next node

menu_template = """

## node start

Is your answer yes or no?

## options

[Y]es!;yes;y: Answer yes. -> handle_answer(answer=yes)
[N]o!;no;n: Answer no. -> handle_answer(answer=no)
[A]bort;abort;a: Answer neither, and abort. -> end

## node end

Thanks for your answer. Goodbye!

"""

evmenu.template2menu(caller, menu_template, {"handle_answer": _handle_answer})

As seen, the _handle_answer is the same, but the menu structure is described in the menu_template string. The template2menu helper uses the template-string and a mapping of callables (we must add _handle_answer here) to build a full EvMenu for us.

Here’s another menu example, where we can choose how to interact with an NPC:

The guard looks at you suspiciously.
"No one is supposed to be in here ..."
he says, a hand on his weapon.
_______________________________________________
 1. Try to bribe him [Cha + 10 gold]
 2. Convince him you work here [Int]
 3. Appeal to his vanity [Cha]
 4. Try to knock him out [Luck + Dex]
 5. Try to run away [Dex]

def _skill_check(caller, raw_string, **kwargs):
    skills = kwargs.get("skills", [])
    gold = kwargs.get("gold", 0)

    # perform skill check here, decide if check passed or not
    # then decide which node-name to return based on
    # the result ...

    return next_node_name

def node_guard(caller, raw_string, **kwarg):
    text = (
        'The guard looks at you suspiciously.\n'
        '"No one is supposed to be in here ..."\n'
        'he says, a hand on his weapon.'
    options = (
        {"desc": "Try to bribe on [Cha + 10 gold]",
         "goto": (_skill_check, {"skills": ["Cha"], "gold": 10})},
        {"desc": "Convince him you work here [Int].",
         "goto": (_skill_check, {"skills": ["Int"]})},
        {"desc": "Appeal to his vanity [Cha]",
         "goto": (_skill_check, {"skills": ["Cha"]})},
        {"desc": "Try to knock him out [Luck + Dex]",
         "goto": (_skill_check, {"skills"" ["Luck", "Dex"]})},
        {"desc": "Try to run away [Dex]",
         "goto": (_skill_check, {"skills": ["Dex"]})}
    return text, options
    )

# EvMenu called below, with all the nodes ...

Note that by skipping the key of the options, we instead get an (auto-generated) list of numbered options to choose from.

Here the _skill_check helper will check (roll your stats, exactly what this means depends on your game) to decide if your approach succeeded. It may then choose to point you to nodes that continue the conversation or maybe dump you into combat!

Launching the menu¶

Initializing the menu is done using a call to the evennia.utils.evmenu.EvMenu class. This is the most common way to do so - from inside a Command:

# in, for example gamedir/commands/command.py

from evennia.utils.evmenu import EvMenu

class CmdTestMenu(Command):

    key = "testcommand"

    def func(self):

	EvMenu(self.caller, "world.mymenu")

When running this command, the menu will start using the menu nodes loaded from mygame/world/mymenu.py. See next section on how to define menu nodes.

The EvMenu has the following optional callsign:

EvMenu(caller, menu_data,
       startnode="start",
       cmdset_mergetype="Replace", cmdset_priority=1,
       auto_quit=True, auto_look=True, auto_help=True,
       cmd_on_exit="look",
       persistent=False,
       startnode_input="",
       session=None,
       debug=False,
       **kwargs)

caller (Object or Account): is a reference to the object using the menu. This object will get a new CmdSet assigned to it, for handling the menu.
menu_data (str, module or dict): is a module or python path to a module where the global-level functions will each be considered to be a menu node. Their names in the module will be the names by which they are referred to in the module. Importantly, function names starting with an underscore _ will be ignored by the loader. Alternatively, this can be a direct mapping {"nodename":function, ...}.
startnode (str): is the name of the menu-node to start the menu at. Changing this means that you can jump into a menu tree at different positions depending on circumstance and thus possibly re-use menu entries.
cmdset_mergetype (str): This is usually one of “Replace” or “Union” (see [CmdSets](Command- Sets). The first means that the menu is exclusive - the user has no access to any other commands while in the menu. The Union mergetype means the menu co-exists with previous commands (and may overload them, so be careful as to what to name your menu entries in this case).
cmdset_priority (int): The priority with which to merge in the menu cmdset. This allows for advanced usage.
auto_quit, auto_look, auto_help (bool): If either of these are True, the menu automatically makes a quit, look or help command available to the user. The main reason why you’d want to turn this off is if you want to use the aliases “q”, “l” or “h” for something in your menu. The auto_help also activates the ability to have arbitrary “tool tips” in your menu node (see below), At least quit is highly recommend - if False, the menu must itself supply an “exit node” (a node without any options), or the user will be stuck in the menu until the server reloads (or eternally if the menu is persistent)!
cmd_on_exit (str): This command string will be executed right after the menu has closed down. From experience, it’s useful to trigger a “look” command to make sure the user is aware of the change of state; but any command can be used. If set to None, no command will be triggered after exiting the menu.
persistent (bool) - if True, the menu will survive a reload (so the user will not be kicked out by the reload - make sure they can exit on their own!)
startnode_input (str or (str, dict) tuple): Pass an input text or a input text + kwargs to the start node as if it was entered on a fictional previous node. This can be very useful in order to start a menu differently depending on the Command’s arguments in which it was initialized.
session (Session): Useful when calling the menu from an Account in MULTISESSION_MODE higher than 2, to make sure only the right Session sees the menu output.
debug (bool): If set, the menudebug command will be made available in the menu. Use it to list the current state of the menu and use menudebug <variable> to inspect a specific state variable from the list.
All other keyword arguments will be available as initial data for the nodes. They will be available in all nodes as properties on caller.ndb._evmenu (see below). These will also survive a reload if the menu is persistent.

You don’t need to store the EvMenu instance anywhere - the very act of initializing it will store it as caller.ndb._evmenu on the caller. This object will be deleted automatically when the menu is exited and you can also use it to store your own temporary variables for access throughout the menu. Temporary variables you store on a persistent _evmenu as it runs will not survive a @reload, only those you set as part of the original EvMenu call.

The Menu nodes¶

The EvMenu nodes consist of functions on one of these forms.

def menunodename1(caller):
    # code
    return text, options

def menunodename2(caller, raw_string):
    # code
    return text, options

def menunodename3(caller, raw_string, **kwargs):
    # code
    return text, options

While all of the above forms are okay, it’s recommended to stick to the third and last form since it gives the most flexibility. The previous forms are mainly there for backwards compatibility with existing menus from a time when EvMenu was less able and may become deprecated at some time in the future.

Input arguments to the node¶

caller (Object or Account): The object using the menu - usually a Character but could also be a Session or Account depending on where the menu is used.
raw_string (str): If this is given, it will be set to the exact text the user entered on the previous node (that is, the command entered to get to this node). On the starting-node of the menu, this will be an empty string, unless startnode_input was set.
kwargs (dict): These extra keyword arguments are extra optional arguments passed to the node when the user makes a choice on the previous node. This may include things like status flags and details about which exact option was chosen (which can be impossible to determine from raw_string alone). Just what is passed in kwargs is up to you when you create the previous node.

Return values from the node¶

Each node function must return two variables, text and options.

text¶

The text variable is either a string or a tuple. This is the simplest form:

text = "Node text"

This is what will be displayed as text in the menu node when entering it. You can modify this dynamically in the node if you want. Returning a None node text text is allowed - this leads to a node with no text and only options.

text = ("Node text", "help text to show with h|elp")

In this form, we also add an optional help text. If auto_help=True when initializing the EvMenu, the user will be able to use h or help to see this text when viewing this node. If the user were to provide a custom option overriding h or help, that will be shown instead.

If auto_help=True and no help text is provided, using h|elp will give a generic error message.

text = ("Node text", {"help topic 1": "Help 1", 
                      ("help topic 2", "alias1", ...): "Help 2", ...})

This is ‘tooltip’ or ‘multi-help category’ mode. This also requires auto_help=True when initializing the EvMenu. By providing a dict as the second element of the text tuple, the user will be able to help about any of these topics. Use a tuple as key to add multiple aliases to the same help entry. This allows the user to get more detailed help text without leaving the given node.

Note that in ‘tooltip’ mode, the normal h|elp command won’t work. The h|elp entry must be added manually in the dict. As an example, this would reproduce the normal help functionality:

text = ("Node text", {("help", "h"): "Help entry...", ...})

options¶

The options list describe all the choices available to the user when viewing this node. If options is returned as None, it means that this node is an Exit node - any text is displayed and then the menu immediately exits, running the exit_cmd if given.

Otherwise, options should be a list (or tuple) of dictionaries, one for each option. If only one option is available, a single dictionary can also be returned. This is how it could look:

def node_test(caller, raw_string, **kwargs):

    text = "A goblin attacks you!"

    options = (
	{"key": ("Attack", "a", "att"),
         "desc": "Strike the enemy with all your might",
         "goto": "node_attack"},
	{"key": ("Defend", "d", "def"),
         "desc": "Hold back and defend yourself",
         "goto": (_defend, {"str": 10, "enemyname": "Goblin"})})

    return text, options

This will produce a menu node looking like this:

A goblin attacks you!
________________________________

Attack: Strike the enemy with all your might
Defend: Hold back and defend yourself

option-key ‘key’¶

The option’s key is what the user should enter in order to choose that option. If given as a tuple, the first string of that tuple will be what is shown on-screen while the rest are aliases for picking that option. In the above example, the user could enter “Attack” (or “attack”, it’s not case-sensitive), “a” or “att” in order to attack the goblin. Aliasing is useful for adding custom coloring to the choice. The first element of the aliasing tuple should then be the colored version, followed by a version without color - since otherwise the user would have to enter the color codes to select that choice.

Note that the key is optional. If no key is given, it will instead automatically be replaced with a running number starting from 1. If removing the key part of each option, the resulting menu node would look like this instead:

A goblin attacks you!
________________________________

1: Strike the enemy with all your might
2: Hold back and defend yourself

Whether you want to use a key or rely on numbers is mostly a matter of style and the type of menu.

EvMenu accepts one important special key given only as "_default". This key is used when a user enters something that does not match any other fixed keys. It is particularly useful for getting user input:

def node_readuser(caller, raw_string, **kwargs):
    text = "Please enter your name"

    options = {"key": "_default",
               "goto": "node_parse_input"}

    return text, options

A "_default" option does not show up in the menu, so the above will just be a node saying "Please enter your name". The name they entered will appear as raw_string in the next node.

option-key ‘desc’¶

This simply contains the description as to what happens when selecting the menu option. For "_default" options or if the key is already long or descriptive, it is not strictly needed. But usually it’s better to keep the key short and put more detail in desc.

option-key ‘goto’¶

This is the operational part of the option and fires only when the user chooses said option. Here are three ways to write it

def _action_two(caller, raw_string, **kwargs):
    # do things ...
    return "calculated_node_to_go_to"

def _action_three(caller, raw_string, **kwargs):
    # do things ...
    return "node_four", {"mode": 4}

def node_select(caller, raw_string, **kwargs):

    text = ("select one",
            "help - they all do different things ...")

    options = ({"desc": "Option one",
		            "goto": "node_one"},
	             {"desc": "Option two",
		            "goto": _action_two},
	             {"desc": "Option three",
		            "goto": (_action_three, {"key": 1, "key2": 2})}
              )

    return text, options

As seen above, goto could just be pointing to a single nodename string - the name of the node to go to. When given like this, EvMenu will look for a node named like this and call its associated function as

    nodename(caller, raw_string, **kwargs)

Here, raw_string is always the input the user entered to make that choice and kwargs are the same as those kwargs that already entered the current node (they are passed on).

Alternatively the goto could point to a “goto-callable”. Such callables are usually defined in the same module as the menu nodes and given names starting with _ (to avoid being parsed as nodes themselves). These callables will be called the same as a node function - callable(caller, raw_string, **kwargs), where raw_string is what the user entered on this node and **kwargs is forwarded from the node’s own input.

The goto option key could also point to a tuple (callable, kwargs) - this allows for customizing the kwargs passed into the goto-callable, for example you could use the same callable but change the kwargs passed into it depending on which option was actually chosen.

The “goto callable” must either return a string "nodename" or a tuple ("nodename", mykwargs). This will lead to the next node being called as either nodename(caller, raw_string, **kwargs) or nodename(caller, raw_string, **mykwargs) - so this allows changing (or replacing) the options going into the next node depending on what option was chosen.

There is one important case - if the goto-callable returns None for a nodename, the current node will run again, possibly with different kwargs. This makes it very easy to re-use a node over and over, for example allowing different options to update some text form being passed and manipulated for every iteration.

Temporary storage¶

When the menu starts, the EvMenu instance is stored on the caller as caller.ndb._evmenu. Through this object you can in principle reach the menu’s internal state if you know what you are doing. This is also a good place to store temporary, more global variables that may be cumbersome to keep passing from node to node via the **kwargs. The _evmnenu will be deleted automatically when the menu closes, meaning you don’t need to worry about cleaning anything up.

If you want permanent state storage, it’s instead better to use an Attribute on caller. Remember that this will remain after the menu closes though, so you need to handle any needed cleanup yourself.

Customizing Menu formatting¶

The EvMenu display of nodes, options etc are controlled by a series of formatting methods on the EvMenu class. To customize these, simply create a new child class of EvMenu and override as needed. Here is an example:

from evennia.utils.evmenu import EvMenu

class MyEvMenu(EvMenu):

    def nodetext_formatter(self, nodetext):
        """
        Format the node text itself.

        Args:
            nodetext (str): The full node text (the text describing the node).

        Returns:
            nodetext (str): The formatted node text.

        """

    def helptext_formatter(self, helptext):
        """
        Format the node's help text

        Args:
            helptext (str): The unformatted help text for the node.

        Returns:
            helptext (str): The formatted help text.

        """

    def options_formatter(self, optionlist):
        """
        Formats the option block.

        Args:
            optionlist (list): List of (key, description) tuples for every
                option related to this node.
            caller (Object, Account or None, optional): The caller of the node.

        Returns:
            options (str): The formatted option display.

        """

    def node_formatter(self, nodetext, optionstext):
        """
        Formats the entirety of the node.

        Args:
            nodetext (str): The node text as returned by `self.nodetext_formatter`.
            optionstext (str): The options display as returned by `self.options_formatter`.
            caller (Object, Account or None, optional): The caller of the node.

        Returns:
            node (str): The formatted node to display.

        """

See evennia/utils/evmenu.py for the details of their default implementations.

EvMenu templating language¶

In evmenu.py are two helper functions parse_menu_template and template2menu that is used to parse a menu template string into an EvMenu:

evmenu.template2menu(caller, menu_template, goto_callables)

One can also do it in two steps, by generate a menutree and using that to call EvMenu normally:

menutree = evmenu.parse_menu_template(caller, menu_template, goto_callables)
EvMenu(caller, menutree)

With this latter solution, one could mix and match normally created menu nodes with those generated by the template engine.

The goto_callables is a mapping {"funcname": callable, ...}, where each callable must be a module-global function on the form funcname(caller, raw_string, **kwargs) (like any goto-callable). The menu_template is a multi-line string on the following form:

menu_template = """

## node node1

Text for node

## options

key1: desc1 -> node2
key2: desc2 -> node3
key3: desc3 -> node4
"""

Each menu node is defined by a ## node <name> containing the text of the node, followed by ## options Also ## NODE and ## OPTIONS work. No python code logics is allowed in the template, this code is not evaluated but parsed. More advanced dynamic usage requires a full node-function.

Except for defining the node/options, # act as comments - everything following will be ignored by the template parser.

Template Options¶

The option syntax is

<key>: [desc ->] nodename or function-call

The ‘desc’ part is optional, and if that is not given, the -> can be skipped too:

key: nodename

The key can both be strings and numbers. Separate the aliases with ;.

key: node1
1: node2
key;k: node3
foobar;foo;bar;f;b: node4

Starting the key with the special letter > indicates that what follows is a glob/regex matcher.

>: node1          - matches empty input
> foo*: node1     - everything starting with foo
> *foo: node3     - everything ending with foo
> [0-9]+?: node4  - regex (all numbers)
> *: node5        - catches everything else (put as last option)

Here’s how to call a goto-function from an option:

key: desc -> myfunc(foo=bar)

For this to work template2menu or parse_menu_template must be given a dict that includes {"myfunc": _actual_myfunc_callable}. All callables to be available in the template must be mapped this way. Goto callables act like normal EvMenu goto-callables and should have a callsign of _actual_myfunc_callable(caller, raw_string, **kwargs) and return the next node (passing dynamic kwargs into the next node does not work with the template

use the full EvMenu if you want advanced dynamic data passing).

Only no or named keywords are allowed in these callables. So

myfunc()         # OK
myfunc(foo=bar)  # OK
myfunc(foo)      # error!

This is because these properties are passed as **kwargs into the goto callable.

Templating example¶

from random import random
from evennia.utils import evmenu

def _gamble(caller, raw_string, **kwargs):

    caller.msg("You roll the dice ...")
    if random() < 0.5:
        return "loose"
    else:
        return "win"

template_string = """

## node start

Death patiently holds out a set of bone dice to you.

"ROLL"

he says.

## options

1: Roll the dice -> gamble()
2: Try to talk yourself out of rolling -> start

## node win

The dice clatter over the stones.

"LOOKS LIKE YOU WIN THIS TIME"

says Death.

# (this ends the menu since there are no options)

## node loose

The dice clatter over the stones.

"YOUR LUCK RAN OUT"

says Death.

"YOU ARE COMING WITH ME."

# (this ends the menu, but what happens next - who knows!)

"""

# map the in-template callable-name to real python code
goto_callables = {"gamble": _gamble}
# this starts the evmenu for the caller
evmenu.template2menu(caller, template_string, goto_callables)

Asking for one-line input¶

This describes two ways for asking for simple questions from the user. Using Python’s input will not work in Evennia. input will block the entire server for everyone until that one player has entered their text, which is not what you want.

The `yield` way¶

In the func method of your Commands (only) you can use Python’s built-in yield command to request input in a similar way to input. It looks like this:

result = yield("Please enter your answer:")

This will send “Please enter your answer” to the Command’s self.caller and then pause at that point. All other players at the server will be unaffected. Once caller enteres a reply, the code execution will continue and you can do stuff with the result. Here is an example:

from evennia import Command
class CmdTestInput(Command):
    key = "test"
    def func(self):
        result = yield("Please enter something:")
        self.caller.msg(f"You entered {result}.")
        result2 = yield("Now enter something else:")
        self.caller.msg(f"You now entered {result2}.")

Using yield is simple and intuitive, but it will only access input from self.caller and you cannot abort or time out the pause until the player has responded. Under the hood, it is actually just a wrapper calling get_input described in the following section.

Important Note: In Python you cannot mix yield and return <value> in the same method. It has to do with yield turning the method into a generator. A return without an argument works, you can just not do return <value>. This is usually not something you need to do in func() anyway, but worth keeping in mind.

The `get_input` way¶

The evmenu module offers a helper function named get_input. This is wrapped by the yield statement which is often easier and more intuitive to use. But get_input offers more flexibility and power if you need it. While in the same module as EvMenu, get_input is technically unrelated to it. The get_input allows you to ask and receive simple one-line input from the user without launching the full power of a menu to do so. To use, call get_input like this:

get_input(caller, prompt, callback)

Here caller is the entity that should receive the prompt for input given as prompt. The callback is a callable function(caller, prompt, user_input) that you define to handle the answer from the user. When run, the caller will see prompt appear on their screens and any text they enter will be sent into the callback for whatever processing you want.

Below is a fully explained callback and example call:

from evennia import Command
from evennia.utils.evmenu import get_input

def callback(caller, prompt, user_input):
    """
    This is a callback you define yourself.

    Args:
        caller (Account or Object): The one being asked
          for input
        prompt (str): A copy of the current prompt
        user_input (str): The input from the account.

    Returns:
        repeat (bool): If not set or False, exit the
          input prompt and clean up. If returning anything
          True, stay in the prompt, which means this callback
          will be called again with the next user input.
    """
    caller.msg(f"When asked '{prompt}', you answered '{user_input}'.")

get_input(caller, "Write something! ", callback)

This will show as

Write something!
> Hello
When asked 'Write something!', you answered 'Hello'.

Normally, the get_input function quits after any input, but as seen in the example docs, you could return True from the callback to repeat the prompt until you pass whatever check you want.

Note: You cannot link consecutive questions by putting a new get_input call inside the callback If you want that you should use an EvMenu instead (see the Repeating the same node example above). Otherwise you can either peek at the implementation of get_input and implement your own mechanism (it’s just using cmdset nesting) or you can look at this extension suggested on the mailing list.

Example: Yes/No prompt¶

Below is an example of a Yes/No prompt using the get_input function:

def yesno(caller, prompt, result):
    if result.lower() in ("y", "yes", "n", "no"):
        # do stuff to handle the yes/no answer
        # ...
        # if we return None/False the prompt state
        # will quit after this
    else:
        # the answer is not on the right yes/no form
        caller.msg("Please answer Yes or No. \n{prompt}")
@        # returning True will make sure the prompt state is not exited
        return True

# ask the question
get_input(caller, "Is Evennia great (Yes/No)?", yesno)

The `@list_node` decorator¶

The evennia.utils.evmenu.list_node is an advanced decorator for use with EvMenu node functions. It is used to quickly create menus for manipulating large numbers of items.

text here
______________________________________________

option1     7. option7      13. option13
option2     8. option8      14. option14
option3     9. option9      [p]revius page
option4    10. option10      page 2
option5    11. option11     [n]ext page
option6    12. option12

The menu will automatically create an multi-page option listing that one can flip through. One can inpect each entry and then select them with prev/next. This is how it is used:

from evennia.utils.evmenu import list_node


...

_options(caller):
    return ['option1', 'option2', ... 'option100']

_select(caller, menuchoice, available_choices):
    # analyze choice
    return "next_node"

@list_node(options, select=_select, pagesize=10)
def node_mylist(caller, raw_string, **kwargs):
    ...

    return text, options

The options argument to list_node is either a list, a generator or a callable returning a list of strings for each option that should be displayed in the node.

The select is a callable in the example above but could also be the name of a menu node. If a callable, the menuchoice argument holds the selection done and available_choices holds all the options available. The callable should return the menu to go to depending on the selection (or None to rerun the same node). If the name of a menu node, the selection will be passed as selection kwarg to that node.

The decorated node itself should return text to display in the node. It must return at least an empty dictionary for its options. It returning options, those will supplement the options auto-created by the list_node decorator.

Example Menus¶

Here is a diagram to help visualize the flow of data from node to node, including goto-callables in-between:

        ┌─
        │  def nodeA(caller, raw_string, **kwargs):
        │      text = "Choose how to operate on 2 and 3."
        │      options = (
        │          {
        │              "key": "A",
        │              "desc": "Multiply 2 with 3",
        │              "goto": (_callback, {"type": "mult", "a": 2, "b": 3})
        │          },                      ───────────────────┬────────────
        │          {                                          │
        │              "key": "B",                            └───────────────┐
        │              "desc": "Add 2 and 3",                                 │
  Node A│              "goto": (_callback, {"type": "add", "a": 2, "b": 3})   │
        │          },                      ─────────────────┬─────────────    │
        │          {                                        │                 │
        │              "key": "C",                          │                 │
        │              "desc": "Show the value 5",          │                 │
        │              "goto": ("node_B", {"c": 5})         │                 │
        │          }                      ───────┐          │                 │
        │      )                                 └──────────┼─────────────────┼───┐
        │      return text, options                         │                 │   │
        └─                                       ┌──────────┘                 │   │
                                                 │                            │   │
                                                 │ ┌──────────────────────────┘   │
        ┌─                                       ▼ ▼                              │
        │  def _callback(caller, raw_string, **kwargs):                           │
        │      if kwargs["type"] == "mult":                                       │
        │          return "node_B", {"c": kwargs["a"] * kwargs["b"]}              │
Goto-   │                           ───────────────┬────────────────              │
callable│                                          │                              │
        │                                          └───────────────────┐          │
        │                                                              │          │
        │      elif kwargs["type"] == "add":                           │          │
        │          return "node_B", {"c": kwargs["a"] + kwargs["b"]}   │          │
        └─                          ────────┬───────────────────────   │          │
                                            │                          │          │
                                            │ ┌────────────────────────┼──────────┘
                                            │ │                        │
                                            │ │ ┌──────────────────────┘
        ┌─                                  ▼ ▼ ▼
        │  def nodeB(caller, raw_string, **kwargs):
  Node B│      text = "Result of operation: " + kwargs["c"]
        │      return text, {}
        └─

        ┌─
   Menu │  EvMenu(caller, {"node_A": nodeA, "node_B": nodeB}, startnode="node_A")
   Start│
        └─

Above we create a very simple/stupid menu (in the EvMenu call at the end) where we map the node identifier "node_A" to the Python function nodeA and "node_B" to the function nodeB.

We start the menu in "node_A" where we get three options A, B and C. Options A and B will route via a a goto-callable _callback that either multiples or adds the numbers 2 and 3 together before continuing to "node_B". Option C routes directly to "node_B", passing the number 5.

In every step, we pass a dict which becomes the ingoing **kwargs in the next step. If we didn’t pass anything (it’s optional), the next step’s **kwargs would just be empty.

More examples:

Simple branching menu - choose from options
Dynamic goto - jumping to different nodes based on response
Set caller properties - a menu that changes things
Getting arbitrary input - entering text
Storing data between nodes - keeping states and information while in the menu
Repeating the same node - validating within the node before moving to the next
Yes/No prompt - entering text with limited possible responses (this is not using EvMenu but the conceptually similar yet technically unrelated get_input helper function accessed as evennia.utils.evmenu.get_input).

Example: Simple branching menu¶

Below is an example of a simple branching menu node leading to different other nodes depending on choice:

# in mygame/world/mychargen.py

def define_character(caller):
    text = \
    """
    What aspect of your character do you want
    to change next?
    """
    options = ({"desc": "Change the name",
                "goto": "set_name"},
               {"desc": "Change the description",
                "goto": "set_description"})
    return text, options

EvMenu(caller, "world.mychargen", startnode="define_character")

This will result in the following node display:

What aspect of your character do you want
to change next?
_________________________
1: Change the name
2: Change the description

Note that since we didn’t specify the “name” key, EvMenu will let the user enter numbers instead. In the following examples we will not include the EvMenu call but just show nodes running inside the menu. Also, since EvMenu also takes a dictionary to describe the menu, we could have called it like this instead in the example:

EvMenu(caller, {"define_character": define_character}, startnode="define_character")

Example: Dynamic goto¶

def _is_in_mage_guild(caller, raw_string, **kwargs):
    if caller.tags.get('mage', category="guild_member"):
        return "mage_guild_welcome"
    else:
        return "mage_guild_blocked"

def enter_guild:
    text = 'You say to the mage guard:'
    options ({'desc': 'I need to get in there.',
              'goto': _is_in_mage_guild},
             {'desc': 'Never mind',
              'goto': 'end_conversation'})
    return text, options

This simple callable goto will analyse what happens depending on who the caller is. The enter_guild node will give you a choice of what to say to the guard. If you try to enter, you will end up in different nodes depending on (in this example) if you have the right Tag set on yourself or not. Note that since we don’t include any ‘key’s in the option dictionary, you will just get to pick between numbers.

Example: Set caller properties¶

Here is an example of passing arguments into the goto callable and use that to influence which node it should go to next:

def _set_attribute(caller, raw_string, **kwargs):
    "Get which attribute to modify and set it"

    attrname, value = kwargs.get("attr", (None, None))
    next_node = kwargs.get("next_node")

    caller.attributes.add(attrname, attrvalue)

    return next_node


def node_background(caller):
    text = \
    f"""
    {caller.key} experienced a traumatic event
    in their childhood. What was it?
    """

    options = ({"key": "death",
                "desc": "A violent death in the family",
                "goto": (_set_attribute, {"attr": ("experienced_violence", True),
					  "next_node": "node_violent_background"})},
               {"key": "betrayal",
                "desc": "The betrayal of a trusted grown-up",
                "goto": (_set_attribute, {"attr": ("experienced_betrayal", True),
					  "next_node": "node_betrayal_background"})})
    return text, options

This will give the following output:

Kovash the magnificent experienced a traumatic event
in their childhood. What was it?
____________________________________________________
death: A violent death in the family
betrayal: The betrayal of a trusted grown-up

Note above how we use the _set_attribute helper function to set the attribute depending on the User’s choice. In thie case the helper function doesn’t know anything about what node called it - we even tell it which nodename it should return, so the choices leads to different paths in the menu. We could also imagine the helper function analyzing what other choices

Example: Get arbitrary input¶

An example of the menu asking the user for input - any input.

def _set_name(caller, raw_string, **kwargs):

    inp = raw_string.strip()

    prev_entry = kwargs.get("prev_entry")

    if not inp:
        # a blank input either means OK or Abort
        if prev_entry:
            caller.key = prev_entry
            caller.msg(f"Set name to {prev_entry}.")
            return "node_background"
        else:
	    caller.msg("Aborted.")
	    return "node_exit"
    else:
        # re-run old node, but pass in the name given
        return None, {"prev_entry": inp}


def enter_name(caller, raw_string, **kwargs):

    # check if we already entered a name before
    prev_entry = kwargs.get("prev_entry")

    if prev_entry:
	text = "Current name: {}.\nEnter another name or <return> to accept."
    else:
	text = "Enter your character's name or <return> to abort."

    options = {"key": "_default",
               "goto": (_set_name, {"prev_entry": prev_entry})}

    return text, options

This will display as

Enter your character's name or <return> to abort.

> Gandalf

Current name: Gandalf
Enter another name or <return> to accept.

>

Set name to Gandalf.

Here we re-use the same node twice for reading the input data from the user. Whatever we enter will be caught by the _default option and passed into the helper function. We also pass along whatever name we have entered before. This allows us to react correctly on an “empty” input - continue to the node named "node_background" if we accept the input or go to an exit node if we presses Return without entering anything. By returning None from the helper function we automatically re-run the previous node, but updating its ingoing kwargs to tell it to display a different text.

Example: Storing data between nodes¶

A convenient way to store data is to store it on the caller.ndb._evmenu which you can reach from every node. The advantage of doing this is that the _evmenu NAttribute will be deleted automatically when you exit the menu.

def _set_name(caller, raw_string, **kwargs):

    caller.ndb._evmenu.charactersheet = {}
    caller.ndb._evmenu.charactersheet['name'] = raw_string
    caller.msg(f"You set your name to {raw_string}")
    return "background"

def node_set_name(caller):
    text = 'Enter your name:'
    options = {'key': '_default',
               'goto': _set_name}

    return text, options

...


def node_view_sheet(caller):
    text = f"Character sheet:\n {self.ndb._evmenu.charactersheet}"

    options = ({"key": "Accept",
                "goto": "finish_chargen"},
	       {"key": "Decline",
                "goto": "start_over"})

    return text, options

Instead of passing the character sheet along from node to node through the kwargs we instead set it up temporarily on caller.ndb._evmenu.charactersheet. This makes it easy to reach from all nodes. At the end we look at it and, if we accept the character the menu will likely save the result to permanent storage and exit.

One point to remember though is that storage on caller.ndb._evmenu is not persistent across @reloads. If you are using a persistent menu (using EvMenu(..., persistent=True) you should use caller.db to store in-menu data like this as well. You must then yourself make sure to clean it when the user exits the menu.

Example: Repeating the same node¶

Sometimes you want to make a chain of menu nodes one after another, but you don’t want the user to be able to continue to the next node until you have verified that what they input in the previous node is ok. A common example is a login menu:

def _check_username(caller, raw_string, **kwargs):
    # we assume lookup_username() exists
    if not lookup_username(raw_string):
	# re-run current node by returning `None`
	caller.msg("|rUsername not found. Try again.")
	return None
    else:
	# username ok - continue to next node
	return "node_password"


def node_username(caller):
    text = "Please enter your user name."
    options = {"key": "_default",
               "goto": _check_username}
    return text, options


def _check_password(caller, raw_string, **kwargs):

    nattempts = kwargs.get("nattempts", 0)
    if nattempts > 3:
	caller.msg("Too many failed attempts. Logging out")
	return "node_abort"
    elif not validate_password(raw_string):
        caller.msg("Password error. Try again.")
	return None, {"nattempts", nattempts + 1}
    else:
	# password accepted
	return "node_login"

def node_password(caller, raw_string, **kwargs):
    text = "Enter your password."
    options = {"key": "_default",
	       "goto": _check_password}
    return text, options

This will display something like

---------------------------
Please enter your username.
---------------------------

> Fo

------------------------------
Username not found. Try again.
______________________________
abort: (back to start)
------------------------------

> Foo

---------------------------
Please enter your password.
---------------------------

> Bar

--------------------------
Password error. Try again.
--------------------------

And so on.

Here the goto-callables will return to the previous node if there is an error. In the case of password attempts, this will tick up the nattempts argument that will get passed on from iteration to iteration until too many attempts have been made.

Defining nodes in a dictionary¶

You can also define your nodes directly in a dictionary to feed into the EvMenu creator.

def mynode(caller):
   # a normal menu node function
   return text, options

menu_data = {"node1": mynode,
             "node2": lambda caller: (
                      "This is the node text",
                     ({"key": "lambda node 1",
                       "desc": "go to node 1 (mynode)",
                       "goto": "node1"},
                      {"key": "lambda node 2",
                       "desc": "go to thirdnode",
                       "goto": "node3"})),
             "node3": lambda caller, raw_string: (
                       # ... etc ) }

# start menu, assuming 'caller' is available from earlier
EvMenu(caller, menu_data, startnode="node1")

The keys of the dictionary become the node identifiers. You can use any callable on the right form to describe each node. If you use Python lambda expressions you can make nodes really on the fly. If you do, the lambda expression must accept one or two arguments and always return a tuple with two elements (the text of the node and its options), same as any menu node function.

Creating menus like this is one way to present a menu that changes with the circumstances - you could for example remove or add nodes before launching the menu depending on some criteria. The drawback is that a lambda expression is much more limited than a full function - for example you can’t use other Python keywords like if inside the body of the lambda.

Unless you are dealing with a relatively simple dynamic menu, defining menus with lambda’s is probably more work than it’s worth: You can create dynamic menus by instead making each node function more clever. See the NPC shop tutorial for an example of this.

Table of Contents

Previous topic

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Links

EvMenu¶

Launching the menu¶

The Menu nodes¶

Input arguments to the node¶

Return values from the node¶

text¶

options¶

option-key ‘key’¶

option-key ‘desc’¶

option-key ‘goto’¶

Temporary storage¶

Customizing Menu formatting¶

EvMenu templating language¶

Template Options¶

Templating example¶

Asking for one-line input¶

The `yield` way¶

The `get_input` way¶

Example: Yes/No prompt¶

The `@list_node` decorator¶

Example Menus¶

Example: Simple branching menu¶

Example: Dynamic goto¶

Example: Set caller properties¶

Example: Get arbitrary input¶

Example: Storing data between nodes¶

Example: Repeating the same node¶

Defining nodes in a dictionary¶

EvMenu¶

Launching the menu¶

The Menu nodes¶

Input arguments to the node¶

Return values from the node¶

text¶

options¶

option-key ‘key’¶

option-key ‘desc’¶

option-key ‘goto’¶

Temporary storage¶

Customizing Menu formatting¶

EvMenu templating language¶

Template Options¶

Templating example¶

Asking for one-line input¶

The yield way¶

The get_input way¶

Example: Yes/No prompt¶

The @list_node decorator¶

Example Menus¶

Example: Simple branching menu¶

Example: Dynamic goto¶

Example: Set caller properties¶

Example: Get arbitrary input¶

Example: Storing data between nodes¶

Example: Repeating the same node¶

Defining nodes in a dictionary¶

The `yield` way¶

The `get_input` way¶

The `@list_node` decorator¶