docutils.parsers.rst.Directive

Base class for reStructuredText directives.

The following attributes may be set by subclasses. They are interpreted by the directive parser (which runs the directive class):

• required_arguments: The number of required arguments (default: 0).

• optional_arguments: The number of optional arguments (default: 0).

• final_argument_whitespace: A boolean, indicating if the final argument may contain whitespace (default: False).

• option_spec: A dictionary, mapping known option names to conversion functions such as int or float (default: {}, no options). Several conversion functions are defined in the directives/__init__.py module.

  Option conversion functions take a single parameter, the option argument (a string or None), validate it and/or convert it to the appropriate form. Conversion functions may raise ValueError and TypeError exceptions.

• has_content: A boolean; True if content is allowed. Client code must handle the case where content is required but not supplied (an empty content list will be supplied).

Arguments are normally single whitespace-separated words. The final argument may contain whitespace and/or newlines if final_argument_whitespace is True.

If the form of the arguments is more complex, specify only one argument (either required or optional) and set final_argument_whitespace to True; the client code must do any context-sensitive parsing.

When a directive implementation is being run, the directive class is instantiated, and the run() method is executed. During instantiation, the following instance variables are set:

• name is the directive type or name (string).
• arguments is the list of positional arguments (strings).
• options is a dictionary mapping option names (strings) to values (type depends on option conversion functions; see option_spec above).
• content is a list of strings, the directive content line by line.
• lineno is the absolute line number of the first line of the directive.
• content_offset is the line offset of the first line of the content from the beginning of the current input. Used when initiating a nested parse.
• block_text is a string containing the entire directive.
• state is the state which called the directive function.
• state_machine is the state machine which controls the state which called the directive function.

Directive functions return a list of nodes which will be inserted into the document tree at the point where the directive was encountered. This can be an empty list if there is nothing to insert.

For ordinary directives, the list must contain body elements or structural elements. Some directives are intended specifically for substitution definitions, and must return a list of Text nodes and/or inline elements (suitable for inline insertion, in place of the substitution reference). Such directives must verify substitution definition context, typically using code like this:

if not isinstance(state, states.SubstitutionDef):
    error = state_machine.reporter.error(
        'Invalid context: the "%s" directive can only be used '
        'within a substitution definition.' % (name),
        nodes.literal_block(block_text, block_text), line=lineno)
    return [error]