CODING_STYLE.md

Evennia Code Style

All code submitted or committed to the Evennia project should aim to follow the guidelines outlined in Python PEP 8. Keeping the code style uniform makes it much easier for people to collaborate and read the code.

A good way to check if your code follows PEP8 is to use the PEP8 tool on your sources.

Main code style specification

• 4-space indentation, NO TABS!
• Unix line endings.
• 100 character line widths
• CamelCase is only used for classes, nothing else.
• All non-global variable names and all function names are to be lowercase, words separated by underscores. Variable names should always be more than two letters long.
• Module-level global variables (only) are to be in CAPITAL letters.
• Imports should be done in this order:
  • Python modules (builtins and standard library)
  • Twisted modules
  • Django modules
  • Evennia library modules (evennia)
  • Evennia contrib modules (evennia.contrib)
• All modules, classes, functions and methods should have doc strings formatted as outlined below.
• All default commands should have a consistent docstring formatted as outlined below.

Code Docstrings

All modules, classes, functions and methods should have docstrings formatted with Google style -inspired indents, using Markdown formatting where needed. Evennia's api2md parser will use this to create pretty API documentation.

Module docstrings

Modules should all start with at least a few lines of docstring at their top describing the contents and purpose of the module.

Example of module docstring (top of file):

"""
This module handles the creation of `Objects` that
are useful in the game ...

"""

Sectioning (# title, ## subtile etc) should not be used in freeform docstrings - this will confuse the sectioning of the auto documentation page and the auto-api will create this automatically. Write just the section name bolded on its own line to mark a section. Beyond sections markdown should be used as needed to format the text.

Code examples should use multi-line syntax highlighting to mark multi-line code blocks, using the "python" identifier. Just indenting code blocks (common in markdown) will not produce the desired look.

When using any code tags (inline or blocks) it's recommended that you don't let the code extend wider than about 70 characters or it will need to be scrolled horizontally in the wiki (this does not affect any other text, only code).

Class docstrings

The root class docstring should describe the over-arching use of the class. It should usually not describe the exact call sequence nor list important methods, this tends to be hard to keep updated as the API develops. Don't use section markers (#, ## etc).

Example of class docstring:

class MyClass(object):
    """
    This class describes the creation of `Objects`. It is useful
    in many situations, such as ...

    """

Function / method docstrings

Example of function or method docstring:

def funcname(a, b, c, d=False, **kwargs):
    """
    This is a brief introduction to the function/class/method

    Args:
        a (str): This is a string argument that we can talk about
            over multiple lines.
        b (int or str): Another argument.
        c (list): A list argument.
        d (bool, optional): An optional keyword argument.

    Keyword Args:
        test (list): A test keyword.

    Returns:
        str: The result of the function.

    Raises:
        RuntimeException: If there is a critical error,
            this is raised.
        IOError: This is only raised if there is a
            problem with the database.

    Notes:
        This is an example function. If `d=True`, something
        amazing will happen.

    """

The syntax is very "loose" but the indentation matters. That is, you should end the block headers (like Args:) with a line break followed by an indent. When you need to break a line you should start the next line with another indent. For consistency with the code we recommend all indents to be 4 spaces wide (no tabs!).

Here are all the supported block headers:

    """
    Args
        argname (freeform type): Description endind with period.
    Keyword Args:
        argname (freeform type): Description.
    Returns/Yields:
        type: Description.
    Raises:
        Exceptiontype: Description.
    Notes/Note/Examples/Example:
        Freeform text.
    """

Parts marked with "freeform" means that you can in principle put any text there using any formatting except for sections markers (#, ## etc). You must also keep indentation to mark which block you are part of. You should normally use the specified format rather than the freeform counterpart (this will produce nicer output) but in some cases the freeform may produce a more compact and readable result (such as when describing an *args or **kwargs statement in general terms). The first self argument of class methods should never be documented.

Note that

"""
Args:
    argname (type, optional): Description.
"""

and

"""
Keyword Args:
   sargname (type): Description.
"""

mean the same thing! Which one is used depends on the function or method documented, but there are no hard rules; If there is a large **kwargs block in the function, using the Keyword Args: block may be a good idea, for a small number of arguments though, just using Args: and marking keywords as optional will shorten the docstring and make it easier to read.

Default Command Docstrings

These represent a special case since Commands in Evennia use their class docstrings to represent the in-game help entry for that command.

All the commands in the default command sets should have their doc-strings formatted on a similar form. For contribs, this is loosened, but if there is no particular reason to use a different form, one should aim to use the same style for contrib-command docstrings as well.

      """
      Short header

      Usage:
        key[/switches, if any] <mandatory args> [optional] choice1||choice2||choice3

      Switches:
        switch1    - description
        switch2    - description

      Examples:
        Usage example and output

      Longer documentation detailing the command.

      """

• Two spaces are used for indentation in all default commands.
• Square brackets [ ] surround optional, skippable arguments.
• Angled brackets < > surround a description of what to write rather than the exact syntax.
• Explicit choices are separated by |. To avoid this being parsed as a color code, use || (this will come out as a single |) or put spaces around the character ("|") if there's plenty of room.
• The Switches and Examples blocks are optional and based on the Command.

Here is the nick command as an example:

      """
      Define a personal alias/nick

      Usage:
        nick[/switches] <nickname> = [<string>]
        alias             ''

      Switches:
        object   - alias an object
        account   - alias an account
        clearall - clear all your aliases
        list     - show all defined aliases (also "nicks" works)

      Examples:
        nick hi = say Hello, I'm Sarah!
        nick/object tom = the tall man

      A 'nick' is a personal shortcut you create for your own use [...]

        """

For commands that require arguments, the policy is for it to return a Usage: string if the command is entered without any arguments. So for such commands, the Command body should contain something to the effect of

      if not self.args:
          self.caller.msg("Usage: nick[/switches] <nickname> = [<string>]")
          return

Tools for auto-linting

black

Automatic pep8 compliant formatting and linting can be performed using the black formatter:

black --line-length 100

PyCharm

The Python IDE Pycharm can auto-generate empty doc-string stubs. The default is to use reStructuredText form, however. To change to Evennia's Google-style docstrings, follow this guide.