Module
docutils.statemachine

A finite state machine specialized for regular-expression-based text filters, this module defines the following classes:

Exception classes:

Functions:

How To Use This Module

(See the individual classes, methods, and attributes for details.)

  1. Import it: import statemachine or from statemachine import .... You will also need to import re.

  2. Derive a subclass of State (or StateWS) for each state in your state machine:

    class MyState(statemachine.State):
    

    Within the state's class definition:

    1. Include a pattern for each transition, in State.patterns:

      patterns = {'atransition': r'pattern', ...}
      
    2. Include a list of initial transitions to be set up automatically, in State.initial_transitions:

      initial_transitions = ['atransition', ...]
      
    3. Define a method for each transition, with the same name as the transition pattern:

      def atransition(self, match, context, next_state):
          # do something
          result = [...]  # a list
          return context, next_state, result
          # context, next_state may be altered
      

      Transition methods may raise an EOFError to cut processing short.

    4. You may wish to override the State.bof() and/or State.eof() implicit transition methods, which handle the beginning- and end-of-file.

    5. In order to handle nested processing, you may wish to override the attributes State.nested_sm and/or State.nested_sm_kwargs.

      If you are using StateWS as a base class, in order to handle nested indented blocks, you may wish to:

      • override the attributes StateWS.indent_sm, StateWS.indent_sm_kwargs, StateWS.known_indent_sm, and/or StateWS.known_indent_sm_kwargs;
      • override the StateWS.blank() method; and/or
      • override or extend the StateWS.indent(), StateWS.known_indent(), and/or StateWS.firstknown_indent() methods.
  3. Create a state machine object:

    sm = StateMachine(state_classes=[MyState, ...],
                      initial_state='MyState')
    
  4. Obtain the input text, which needs to be converted into a tab-free list of one-line strings. For example, to read text from a file called 'inputfile':

    input_string = open('inputfile').read()
    input_lines = statemachine.string2lines(input_string)
    
  5. Run the state machine on the input text and collect the results, a list:

    results = sm.run(input_lines)
    
  6. Remove any lingering circular references:

    sm.unlink()