EvMenu

Introduction

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:

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]

This is an example of a menu node. Think of a node as a point where the menu stops printing text and waits for user to give some input. By jumping to different nodes depending on the input, a menu is constructed.

Ways to create the menu

node functions

The native way to define an EvMenu is to define Python functions, one per node. It will load all those functions/nodes either from a module or by being passed a dictionary mapping the node’s names to said functions, like {"nodename": <function>, ...}. Since you are dealing with raw code, this is by far the most powerful way - for example you could have dynamic nodes that change content depending on game context, time and what you picked before.

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:

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

from evennia.utils.evmenu import EvMenu

class CmdTestMenu(Command):

    key = "testcommand"

    def func(self):

        EvMenu(caller, "world.mymenu")

When running this command, the menu will start using the menu nodes loaded from mygame/world/mymenu.py and use this to build the menu-tree - each function name becomes the name of a node in the tree. See next section on how to define menu nodes.

Alternatively, you could pass the menu-tree to EvMenu directly:

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  menutree = {"start": nodestartfunc,
              "node1": nodefunc1,
              "node2": nodefunc2,, ...}
  EvMenu(caller, menutree)

This menutree can also be generated from an EvMenu template

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   from evennia.utils.evmenu import parse_menu_template
  
   menutree = parse_menu_template(caller, template_string, goto_callables)
   EvMenu(caller, menutree)

The template_string and goto_callables are described in Template language section.

The EvMenu class

The EvMenu has the following optional callsign:

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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. Nevertheless, 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_MODDE 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._menutree (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._menutree 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 _menutree 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.

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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.

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 function must return two variables, text and options.

text

The text variable is a string or tuple. This text is what will be displayed when the user reaches this node. If this is a tuple, then the first element of the tuple will be considered the displayed text and the second the help-text to display when the user enters the help command on this node.

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    text = ("This is the text to display", "This is the help text for this node")

Returning a None text is allowed and simply leads to a node with no text and only options. If the help text is not given, the menu will give a generic error message when using help.

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:

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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:

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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

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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

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    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.

The EvMenu also supports the exec option key. This allows for running a callable before the goto-callable. This functionality comes from a time before goto could be a callable and is deprecated as of Evennia 0.8. Use goto for all functionality where you’d before use exec.

Temporary storage

When the menu starts, the EvMenu instance is stored on the caller as caller.ndb._menutree. 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 _menutree 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:

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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

The EvMenu is very powerful and flexible. But often your menu is simple enough to not require the full power of EvMenu. For this you can use the Evmenu templating language.

This is how the templating is used:

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from evennia.utils.evmenu import parse_menu_template, EvMenu

template_string = "(will be described below)"
# this could be empty if you don't need to access any callables
# in your template
goto_callables = {"mycallable1": function, ...}

# generate the menutree
menutree = parse_menu_template(caller, template_string, goto_callables)
# a normal EvMenu call
EvMenu(caller, menutree, ...)

… So the parse_menu_template is just another way to generate the menutree dict needed by EvMenu - after this EvMenu works normally.

The good thing with this two-step procedude is that you can mix- and match - if you wanted you could insert a normal, fully flexible function-based node-function in the menutree before passing the whole thing into EvMenu and get the best of both worlds. It also makes it easy to substitute base EvMenu with a child class that changes the menu display.

… But if you really don’t need any such customization, you can also apply the template in one step using the template2menu helper:

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from evennia.utils.evmenu import template2menu

template_string = "(will be described below)"
goto_callables = {"mycallable1": function, ...}

template2menu(caller, template_string, goto_callables, startnode="start", ...)

In addition to the template-related arguments, template2menu takes all the same **kwargs as EvMenu and will parse the template and start the menu for you in one go.

The templating string

The template is a normal string with a very simple format. Each node begins with a marker ## Node <name of node>, follwowed by a ## Options separator (the Node and Options are case-insensitive).

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template_string = """

## NODE start

<text for the node>

## OPTIONS

# this is a comment. Only line-comments are allowed.

key;alias;alias: description -> goto_str_or_callable
key;alias;alias: goto_str_or_callable
>pattern: goto_str_or_callable

"""
  • The text after ## NODE defines the name of the node. This must be unique within the menu because this is what you use for goto statements. The name could have spaces.

  • The area between ## NODE and ## OPTIONS contains the text of the node. It can have normal formatting and will retain intentation.

  • The ## OPTIONS section, until the next ## NODE or the end of the string, holds the options, one per line.

  • Option-indenting is ignored but can be useful for readability.

  • The options-section can also have line-comments, marked by starting the line with #.

  • A node without a following ## OPTIONS section indicates an end node, and reaching it will print the text and immediately exit the menu (same as for regular EvMenu).

Templating options format

The normal, full syntax is:

key;alias;alias: description -> goto_str_or_callable

An example would be

next;n: Go to node Two -> node2

In the menu, this will become an option

next: Go to node Two

where you can enter next or n to go to the menu node named node2.

To skip the description, just add the goto without the ->:

next;n: node2

This will create a menu option without any description:

next

A special key is >. This acts as a pattern matcher. Between > and the : one can fit an optional pattern. This pattern will first be parsed with glob-style parsing and then with regex, and only if the player’s input matches either will the option be chosen. An input-matching option cannot have a description.

  # this matches the empty string (just pressing return)
  >: node2

  # this matches input starting with 'test' (regex match)
  > ^test.+?: testnode

  # this matches any number input (regex match)
  > [0-9]+?: countnode

  # this matches everything not covered by previous options
  # (glob-matching, space is stripped without quotes)
  > *: node3

You can have multiple pattern-matchers for a node but remember that options are checked in the order they are listed. So make sure to put your pattern-matchers in decending order of generality; if you have a ‘catch-all’ pattern, it should be put last or those behind it will never be tried.

   next;n: node2
   back;b: node1
   >: node2

The above would give you the option to write next/back but you can also just press return to move on to the next node.

Templating goto-callables

Instead of giving the name of a node to go to, you can also give the name of a goto_callable, which in turn returns the name of the node to go to. You tell the template it’s a callable by simply adding () at the end.

next: Go to node 2 -> goto_node2()

You can also add keyword arguments:

back: myfunction(from=foo)

Note: ONLY keyword-arguments are supported! Trying to pass a positional argument will lead to an error.

The contents of the kwargs-values will be evaluated by literal_eval so you don’t need to add quotes to strings unless they have spaces in them. Numbers will be converted correctly, but more complex input structures (like lists or dicts) will not - if you want more complex input you should use a full function-based EvMenu node instead.

The goto-callable is defined just like any Evmenu goto-func. You must always use the full form (including **kwargs):

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def mygotocallable(caller, raw_string, **kwargs):
  # ...
  return "nodename_to_goto"

Return None to re-run the current node. Any keyword arguments you specify in your template will be passed to your goto-callable in **kwargs. Unlike in regular EvMenu nodes you can’t return kwargs to pass it between nodes and other dynamic tricks.

All goto-callables you use in your menu-template must be added to the goto_callable mapping that you pass to parse_menu_template or template2menu.

Templating example to show all possible options:

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template_string = """

## NODE start

This is the text of the start node.
Both ## NODE, ## node or ## Node works. The node-name can have
spaces.

The text area can have multiple lines, line breaks etc.

## OPTIONS

    # here starts the option-defition
    # comments are only allowed from beginning of line.
    # Indenting is not necessary, but good for readability

    1: Option number 1 -> node1
    2: Option number 2 -> node2
    next: This steps next -> go_back()
    # the -> can be ignored if there is no desc
    back: go_back(from_node=start)
    abort: abort

# ----------------------------------- this is ignored

## NODE node1

Text for Node1. Enter a message!
<return> to go back.

## options

    # Starting the option-line with >
    # allows to perform different actions depending on
    # what is inserted.

    # this catches everything starting with foo
    > foo*: handle_foo_message()

    # regex are also allowed (this catches number inputs)
    > [0-9]+?: handle_numbers()

    # this catches the empty return
    >: start

    # this catches everything else
    > *: handle_message(from_node=node1)

# -----------------------------------------

## NODE node2

Text for Node2. Just go back.

## options

    >: start

# node abort

This exits the menu since there is no `## options` section.


"""

# we assume the callables are defined earlier
goto_callables = {"go_back": go_back_func,
                  "handle_foo_message": handle_message,
                  "handle_numbers": my_number_handler,
                  "handle_message": handle_message2}

# boom - a menu
template2menu(caller, template_string, goto_callables)

Examples:

Example: Simple branching menu

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

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# 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:

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

Example: Dynamic goto

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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:

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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 = \
    """
    {} experienced a traumatic event
    in their childhood. What was it?
    """.format(caller.key}

    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.

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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("Set name to {}.".format(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._menutree which you can reach from every node. The advantage of doing this is that the _menutree NAttribute will be deleted automatically when you exit the menu.

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

    caller.ndb._menutree.charactersheet = {}
    caller.ndb._menutree.charactersheet['name'] = raw_string
    caller.msg("You set your name to {}".format(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 = "Character sheet:\n {}".format(self.ndb._menutree.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._menutree.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._menutree 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:

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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.

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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.

Ask for simple 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:

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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:

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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:

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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:

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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:

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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
______________________________________________

1. option1     7. option7      13. option13
2. option2     8. option8      14. option14
3. option3     9. option9      [p]revius page
4. option4    10. option10      page 2
5. option5    11. option11     [n]ext page
6. 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:

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from evennia.utils.evmenu import list_node


...

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

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

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

    # the decorator auto-creates the options; any options
    # returned here would be appended to the auto-options
    return node_text, {}

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.

Assorted notes

The EvMenu is implemented using Commands. When you start a new EvMenu, the user of the menu will be assigned a CmdSet with the commands they need to navigate the menu. This means that if you were to, from inside the menu, assign a new command set to the caller, you may override the Menu Cmdset and kill the menu. If you want to assign cmdsets to the caller as part of the menu, you should store the cmdset on caller.ndb._menutree and wait to actually assign it until the exit node.