| # $Id: statemachine.py 6388 2010-08-13 12:24:34Z milde $ |
| # Author: David Goodger <goodger@python.org> |
| # Copyright: This module has been placed in the public domain. |
| |
| """ |
| A finite state machine specialized for regular-expression-based text filters, |
| this module defines the following classes: |
| |
| - `StateMachine`, a state machine |
| - `State`, a state superclass |
| - `StateMachineWS`, a whitespace-sensitive version of `StateMachine` |
| - `StateWS`, a state superclass for use with `StateMachineWS` |
| - `SearchStateMachine`, uses `re.search()` instead of `re.match()` |
| - `SearchStateMachineWS`, uses `re.search()` instead of `re.match()` |
| - `ViewList`, extends standard Python lists. |
| - `StringList`, string-specific ViewList. |
| |
| Exception classes: |
| |
| - `StateMachineError` |
| - `UnknownStateError` |
| - `DuplicateStateError` |
| - `UnknownTransitionError` |
| - `DuplicateTransitionError` |
| - `TransitionPatternNotFound` |
| - `TransitionMethodNotFound` |
| - `UnexpectedIndentationError` |
| - `TransitionCorrection`: Raised to switch to another transition. |
| - `StateCorrection`: Raised to switch to another state & transition. |
| |
| Functions: |
| |
| - `string2lines()`: split a multi-line string into a list of one-line strings |
| |
| |
| 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: |
| |
| a) Include a pattern for each transition, in `State.patterns`:: |
| |
| patterns = {'atransition': r'pattern', ...} |
| |
| b) Include a list of initial transitions to be set up automatically, in |
| `State.initial_transitions`:: |
| |
| initial_transitions = ['atransition', ...] |
| |
| c) 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. |
| |
| d) You may wish to override the `State.bof()` and/or `State.eof()` implicit |
| transition methods, which handle the beginning- and end-of-file. |
| |
| e) 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() |
| """ |
| |
| __docformat__ = 'restructuredtext' |
| |
| import sys |
| import re |
| import types |
| import unicodedata |
| |
| |
| class StateMachine: |
| |
| """ |
| A finite state machine for text filters using regular expressions. |
| |
| The input is provided in the form of a list of one-line strings (no |
| newlines). States are subclasses of the `State` class. Transitions consist |
| of regular expression patterns and transition methods, and are defined in |
| each state. |
| |
| The state machine is started with the `run()` method, which returns the |
| results of processing in a list. |
| """ |
| |
| def __init__(self, state_classes, initial_state, debug=0): |
| """ |
| Initialize a `StateMachine` object; add state objects. |
| |
| Parameters: |
| |
| - `state_classes`: a list of `State` (sub)classes. |
| - `initial_state`: a string, the class name of the initial state. |
| - `debug`: a boolean; produce verbose output if true (nonzero). |
| """ |
| |
| self.input_lines = None |
| """`StringList` of input lines (without newlines). |
| Filled by `self.run()`.""" |
| |
| self.input_offset = 0 |
| """Offset of `self.input_lines` from the beginning of the file.""" |
| |
| self.line = None |
| """Current input line.""" |
| |
| self.line_offset = -1 |
| """Current input line offset from beginning of `self.input_lines`.""" |
| |
| self.debug = debug |
| """Debugging mode on/off.""" |
| |
| self.initial_state = initial_state |
| """The name of the initial state (key to `self.states`).""" |
| |
| self.current_state = initial_state |
| """The name of the current state (key to `self.states`).""" |
| |
| self.states = {} |
| """Mapping of {state_name: State_object}.""" |
| |
| self.add_states(state_classes) |
| |
| self.observers = [] |
| """List of bound methods or functions to call whenever the current |
| line changes. Observers are called with one argument, ``self``. |
| Cleared at the end of `run()`.""" |
| |
| def unlink(self): |
| """Remove circular references to objects no longer required.""" |
| for state in self.states.values(): |
| state.unlink() |
| self.states = None |
| |
| def run(self, input_lines, input_offset=0, context=None, |
| input_source=None, initial_state=None): |
| """ |
| Run the state machine on `input_lines`. Return results (a list). |
| |
| Reset `self.line_offset` and `self.current_state`. Run the |
| beginning-of-file transition. Input one line at a time and check for a |
| matching transition. If a match is found, call the transition method |
| and possibly change the state. Store the context returned by the |
| transition method to be passed on to the next transition matched. |
| Accumulate the results returned by the transition methods in a list. |
| Run the end-of-file transition. Finally, return the accumulated |
| results. |
| |
| Parameters: |
| |
| - `input_lines`: a list of strings without newlines, or `StringList`. |
| - `input_offset`: the line offset of `input_lines` from the beginning |
| of the file. |
| - `context`: application-specific storage. |
| - `input_source`: name or path of source of `input_lines`. |
| - `initial_state`: name of initial state. |
| """ |
| self.runtime_init() |
| if isinstance(input_lines, StringList): |
| self.input_lines = input_lines |
| else: |
| self.input_lines = StringList(input_lines, source=input_source) |
| self.input_offset = input_offset |
| self.line_offset = -1 |
| self.current_state = initial_state or self.initial_state |
| if self.debug: |
| print >>sys.stderr, ( |
| '\nStateMachine.run: input_lines (line_offset=%s):\n| %s' |
| % (self.line_offset, '\n| '.join(self.input_lines))) |
| transitions = None |
| results = [] |
| state = self.get_state() |
| try: |
| if self.debug: |
| print >>sys.stderr, ('\nStateMachine.run: bof transition') |
| context, result = state.bof(context) |
| results.extend(result) |
| while 1: |
| try: |
| try: |
| self.next_line() |
| if self.debug: |
| source, offset = self.input_lines.info( |
| self.line_offset) |
| print >>sys.stderr, ( |
| '\nStateMachine.run: line (source=%r, ' |
| 'offset=%r):\n| %s' |
| % (source, offset, self.line)) |
| context, next_state, result = self.check_line( |
| context, state, transitions) |
| except EOFError: |
| if self.debug: |
| print >>sys.stderr, ( |
| '\nStateMachine.run: %s.eof transition' |
| % state.__class__.__name__) |
| result = state.eof(context) |
| results.extend(result) |
| break |
| else: |
| results.extend(result) |
| except TransitionCorrection, exception: |
| self.previous_line() # back up for another try |
| transitions = (exception.args[0],) |
| if self.debug: |
| print >>sys.stderr, ( |
| '\nStateMachine.run: TransitionCorrection to ' |
| 'state "%s", transition %s.' |
| % (state.__class__.__name__, transitions[0])) |
| continue |
| except StateCorrection, exception: |
| self.previous_line() # back up for another try |
| next_state = exception.args[0] |
| if len(exception.args) == 1: |
| transitions = None |
| else: |
| transitions = (exception.args[1],) |
| if self.debug: |
| print >>sys.stderr, ( |
| '\nStateMachine.run: StateCorrection to state ' |
| '"%s", transition %s.' |
| % (next_state, transitions[0])) |
| else: |
| transitions = None |
| state = self.get_state(next_state) |
| except: |
| if self.debug: |
| self.error() |
| raise |
| self.observers = [] |
| return results |
| |
| def get_state(self, next_state=None): |
| """ |
| Return current state object; set it first if `next_state` given. |
| |
| Parameter `next_state`: a string, the name of the next state. |
| |
| Exception: `UnknownStateError` raised if `next_state` unknown. |
| """ |
| if next_state: |
| if self.debug and next_state != self.current_state: |
| print >>sys.stderr, \ |
| ('\nStateMachine.get_state: Changing state from ' |
| '"%s" to "%s" (input line %s).' |
| % (self.current_state, next_state, |
| self.abs_line_number())) |
| self.current_state = next_state |
| try: |
| return self.states[self.current_state] |
| except KeyError: |
| raise UnknownStateError(self.current_state) |
| |
| def next_line(self, n=1): |
| """Load `self.line` with the `n`'th next line and return it.""" |
| try: |
| try: |
| self.line_offset += n |
| self.line = self.input_lines[self.line_offset] |
| except IndexError: |
| self.line = None |
| raise EOFError |
| return self.line |
| finally: |
| self.notify_observers() |
| |
| def is_next_line_blank(self): |
| """Return 1 if the next line is blank or non-existant.""" |
| try: |
| return not self.input_lines[self.line_offset + 1].strip() |
| except IndexError: |
| return 1 |
| |
| def at_eof(self): |
| """Return 1 if the input is at or past end-of-file.""" |
| return self.line_offset >= len(self.input_lines) - 1 |
| |
| def at_bof(self): |
| """Return 1 if the input is at or before beginning-of-file.""" |
| return self.line_offset <= 0 |
| |
| def previous_line(self, n=1): |
| """Load `self.line` with the `n`'th previous line and return it.""" |
| self.line_offset -= n |
| if self.line_offset < 0: |
| self.line = None |
| else: |
| self.line = self.input_lines[self.line_offset] |
| self.notify_observers() |
| return self.line |
| |
| def goto_line(self, line_offset): |
| """Jump to absolute line offset `line_offset`, load and return it.""" |
| try: |
| try: |
| self.line_offset = line_offset - self.input_offset |
| self.line = self.input_lines[self.line_offset] |
| except IndexError: |
| self.line = None |
| raise EOFError |
| return self.line |
| finally: |
| self.notify_observers() |
| |
| def get_source(self, line_offset): |
| """Return source of line at absolute line offset `line_offset`.""" |
| return self.input_lines.source(line_offset - self.input_offset) |
| |
| def abs_line_offset(self): |
| """Return line offset of current line, from beginning of file.""" |
| return self.line_offset + self.input_offset |
| |
| def abs_line_number(self): |
| """Return line number of current line (counting from 1).""" |
| return self.line_offset + self.input_offset + 1 |
| |
| def get_source_and_line(self, lineno=None): |
| """Return (source, line) tuple for current or given line number. |
| |
| Looks up the source and line number in the `self.input_lines` |
| StringList instance to count for included source files. |
| |
| If the optional argument `lineno` is given, convert it from an |
| absolute line number to the corresponding (source, line) pair. |
| """ |
| if lineno is None: |
| offset = self.line_offset |
| else: |
| offset = lineno - self.input_offset - 1 |
| try: |
| src, srcoffset = self.input_lines.info(offset) |
| srcline = srcoffset + 1 |
| except (TypeError): |
| # line is None if index is "Just past the end" |
| src, srcline = self.get_source_and_line(offset + self.input_offset) |
| return src, srcline + 1 |
| except (IndexError): # `offset` is off the list |
| src, srcline = None, None |
| # raise AssertionError('cannot find line %d in %s lines' % |
| # (offset, len(self.input_lines))) |
| # # list(self.input_lines.lines()))) |
| # assert offset == srcoffset, str(self.input_lines) |
| # print "get_source_and_line(%s):" % lineno, |
| # print offset + 1, '->', src, srcline |
| # print self.input_lines |
| return (src, srcline) |
| |
| def insert_input(self, input_lines, source): |
| self.input_lines.insert(self.line_offset + 1, '', |
| source='internal padding after '+source, |
| offset=len(input_lines)) |
| self.input_lines.insert(self.line_offset + 1, '', |
| source='internal padding before '+source, |
| offset=-1) |
| self.input_lines.insert(self.line_offset + 2, |
| StringList(input_lines, source)) |
| |
| def get_text_block(self, flush_left=0): |
| """ |
| Return a contiguous block of text. |
| |
| If `flush_left` is true, raise `UnexpectedIndentationError` if an |
| indented line is encountered before the text block ends (with a blank |
| line). |
| """ |
| try: |
| block = self.input_lines.get_text_block(self.line_offset, |
| flush_left) |
| self.next_line(len(block) - 1) |
| return block |
| except UnexpectedIndentationError, error: |
| block, source, lineno = error.args |
| self.next_line(len(block) - 1) # advance to last line of block |
| raise |
| |
| def check_line(self, context, state, transitions=None): |
| """ |
| Examine one line of input for a transition match & execute its method. |
| |
| Parameters: |
| |
| - `context`: application-dependent storage. |
| - `state`: a `State` object, the current state. |
| - `transitions`: an optional ordered list of transition names to try, |
| instead of ``state.transition_order``. |
| |
| Return the values returned by the transition method: |
| |
| - context: possibly modified from the parameter `context`; |
| - next state name (`State` subclass name); |
| - the result output of the transition, a list. |
| |
| When there is no match, ``state.no_match()`` is called and its return |
| value is returned. |
| """ |
| if transitions is None: |
| transitions = state.transition_order |
| state_correction = None |
| if self.debug: |
| print >>sys.stderr, ( |
| '\nStateMachine.check_line: state="%s", transitions=%r.' |
| % (state.__class__.__name__, transitions)) |
| for name in transitions: |
| pattern, method, next_state = state.transitions[name] |
| match = pattern.match(self.line) |
| if match: |
| if self.debug: |
| print >>sys.stderr, ( |
| '\nStateMachine.check_line: Matched transition ' |
| '"%s" in state "%s".' |
| % (name, state.__class__.__name__)) |
| return method(match, context, next_state) |
| else: |
| if self.debug: |
| print >>sys.stderr, ( |
| '\nStateMachine.check_line: No match in state "%s".' |
| % state.__class__.__name__) |
| return state.no_match(context, transitions) |
| |
| def add_state(self, state_class): |
| """ |
| Initialize & add a `state_class` (`State` subclass) object. |
| |
| Exception: `DuplicateStateError` raised if `state_class` was already |
| added. |
| """ |
| statename = state_class.__name__ |
| if statename in self.states: |
| raise DuplicateStateError(statename) |
| self.states[statename] = state_class(self, self.debug) |
| |
| def add_states(self, state_classes): |
| """ |
| Add `state_classes` (a list of `State` subclasses). |
| """ |
| for state_class in state_classes: |
| self.add_state(state_class) |
| |
| def runtime_init(self): |
| """ |
| Initialize `self.states`. |
| """ |
| for state in self.states.values(): |
| state.runtime_init() |
| |
| def error(self): |
| """Report error details.""" |
| type, value, module, line, function = _exception_data() |
| print >>sys.stderr, '%s: %s' % (type, value) |
| print >>sys.stderr, 'input line %s' % (self.abs_line_number()) |
| print >>sys.stderr, ('module %s, line %s, function %s' |
| % (module, line, function)) |
| |
| def attach_observer(self, observer): |
| """ |
| The `observer` parameter is a function or bound method which takes two |
| arguments, the source and offset of the current line. |
| """ |
| self.observers.append(observer) |
| |
| def detach_observer(self, observer): |
| self.observers.remove(observer) |
| |
| def notify_observers(self): |
| for observer in self.observers: |
| try: |
| info = self.input_lines.info(self.line_offset) |
| except IndexError: |
| info = (None, None) |
| observer(*info) |
| |
| |
| class State: |
| |
| """ |
| State superclass. Contains a list of transitions, and transition methods. |
| |
| Transition methods all have the same signature. They take 3 parameters: |
| |
| - An `re` match object. ``match.string`` contains the matched input line, |
| ``match.start()`` gives the start index of the match, and |
| ``match.end()`` gives the end index. |
| - A context object, whose meaning is application-defined (initial value |
| ``None``). It can be used to store any information required by the state |
| machine, and the retured context is passed on to the next transition |
| method unchanged. |
| - The name of the next state, a string, taken from the transitions list; |
| normally it is returned unchanged, but it may be altered by the |
| transition method if necessary. |
| |
| Transition methods all return a 3-tuple: |
| |
| - A context object, as (potentially) modified by the transition method. |
| - The next state name (a return value of ``None`` means no state change). |
| - The processing result, a list, which is accumulated by the state |
| machine. |
| |
| Transition methods may raise an `EOFError` to cut processing short. |
| |
| There are two implicit transitions, and corresponding transition methods |
| are defined: `bof()` handles the beginning-of-file, and `eof()` handles |
| the end-of-file. These methods have non-standard signatures and return |
| values. `bof()` returns the initial context and results, and may be used |
| to return a header string, or do any other processing needed. `eof()` |
| should handle any remaining context and wrap things up; it returns the |
| final processing result. |
| |
| Typical applications need only subclass `State` (or a subclass), set the |
| `patterns` and `initial_transitions` class attributes, and provide |
| corresponding transition methods. The default object initialization will |
| take care of constructing the list of transitions. |
| """ |
| |
| patterns = None |
| """ |
| {Name: pattern} mapping, used by `make_transition()`. Each pattern may |
| be a string or a compiled `re` pattern. Override in subclasses. |
| """ |
| |
| initial_transitions = None |
| """ |
| A list of transitions to initialize when a `State` is instantiated. |
| Each entry is either a transition name string, or a (transition name, next |
| state name) pair. See `make_transitions()`. Override in subclasses. |
| """ |
| |
| nested_sm = None |
| """ |
| The `StateMachine` class for handling nested processing. |
| |
| If left as ``None``, `nested_sm` defaults to the class of the state's |
| controlling state machine. Override it in subclasses to avoid the default. |
| """ |
| |
| nested_sm_kwargs = None |
| """ |
| Keyword arguments dictionary, passed to the `nested_sm` constructor. |
| |
| Two keys must have entries in the dictionary: |
| |
| - Key 'state_classes' must be set to a list of `State` classes. |
| - Key 'initial_state' must be set to the name of the initial state class. |
| |
| If `nested_sm_kwargs` is left as ``None``, 'state_classes' defaults to the |
| class of the current state, and 'initial_state' defaults to the name of |
| the class of the current state. Override in subclasses to avoid the |
| defaults. |
| """ |
| |
| def __init__(self, state_machine, debug=0): |
| """ |
| Initialize a `State` object; make & add initial transitions. |
| |
| Parameters: |
| |
| - `statemachine`: the controlling `StateMachine` object. |
| - `debug`: a boolean; produce verbose output if true (nonzero). |
| """ |
| |
| self.transition_order = [] |
| """A list of transition names in search order.""" |
| |
| self.transitions = {} |
| """ |
| A mapping of transition names to 3-tuples containing |
| (compiled_pattern, transition_method, next_state_name). Initialized as |
| an instance attribute dynamically (instead of as a class attribute) |
| because it may make forward references to patterns and methods in this |
| or other classes. |
| """ |
| |
| self.add_initial_transitions() |
| |
| self.state_machine = state_machine |
| """A reference to the controlling `StateMachine` object.""" |
| |
| self.debug = debug |
| """Debugging mode on/off.""" |
| |
| if self.nested_sm is None: |
| self.nested_sm = self.state_machine.__class__ |
| if self.nested_sm_kwargs is None: |
| self.nested_sm_kwargs = {'state_classes': [self.__class__], |
| 'initial_state': self.__class__.__name__} |
| |
| def runtime_init(self): |
| """ |
| Initialize this `State` before running the state machine; called from |
| `self.state_machine.run()`. |
| """ |
| pass |
| |
| def unlink(self): |
| """Remove circular references to objects no longer required.""" |
| self.state_machine = None |
| |
| def add_initial_transitions(self): |
| """Make and add transitions listed in `self.initial_transitions`.""" |
| if self.initial_transitions: |
| names, transitions = self.make_transitions( |
| self.initial_transitions) |
| self.add_transitions(names, transitions) |
| |
| def add_transitions(self, names, transitions): |
| """ |
| Add a list of transitions to the start of the transition list. |
| |
| Parameters: |
| |
| - `names`: a list of transition names. |
| - `transitions`: a mapping of names to transition tuples. |
| |
| Exceptions: `DuplicateTransitionError`, `UnknownTransitionError`. |
| """ |
| for name in names: |
| if name in self.transitions: |
| raise DuplicateTransitionError(name) |
| if name not in transitions: |
| raise UnknownTransitionError(name) |
| self.transition_order[:0] = names |
| self.transitions.update(transitions) |
| |
| def add_transition(self, name, transition): |
| """ |
| Add a transition to the start of the transition list. |
| |
| Parameter `transition`: a ready-made transition 3-tuple. |
| |
| Exception: `DuplicateTransitionError`. |
| """ |
| if name in self.transitions: |
| raise DuplicateTransitionError(name) |
| self.transition_order[:0] = [name] |
| self.transitions[name] = transition |
| |
| def remove_transition(self, name): |
| """ |
| Remove a transition by `name`. |
| |
| Exception: `UnknownTransitionError`. |
| """ |
| try: |
| del self.transitions[name] |
| self.transition_order.remove(name) |
| except: |
| raise UnknownTransitionError(name) |
| |
| def make_transition(self, name, next_state=None): |
| """ |
| Make & return a transition tuple based on `name`. |
| |
| This is a convenience function to simplify transition creation. |
| |
| Parameters: |
| |
| - `name`: a string, the name of the transition pattern & method. This |
| `State` object must have a method called '`name`', and a dictionary |
| `self.patterns` containing a key '`name`'. |
| - `next_state`: a string, the name of the next `State` object for this |
| transition. A value of ``None`` (or absent) implies no state change |
| (i.e., continue with the same state). |
| |
| Exceptions: `TransitionPatternNotFound`, `TransitionMethodNotFound`. |
| """ |
| if next_state is None: |
| next_state = self.__class__.__name__ |
| try: |
| pattern = self.patterns[name] |
| if not hasattr(pattern, 'match'): |
| pattern = re.compile(pattern) |
| except KeyError: |
| raise TransitionPatternNotFound( |
| '%s.patterns[%r]' % (self.__class__.__name__, name)) |
| try: |
| method = getattr(self, name) |
| except AttributeError: |
| raise TransitionMethodNotFound( |
| '%s.%s' % (self.__class__.__name__, name)) |
| return (pattern, method, next_state) |
| |
| def make_transitions(self, name_list): |
| """ |
| Return a list of transition names and a transition mapping. |
| |
| Parameter `name_list`: a list, where each entry is either a transition |
| name string, or a 1- or 2-tuple (transition name, optional next state |
| name). |
| """ |
| stringtype = type('') |
| names = [] |
| transitions = {} |
| for namestate in name_list: |
| if type(namestate) is stringtype: |
| transitions[namestate] = self.make_transition(namestate) |
| names.append(namestate) |
| else: |
| transitions[namestate[0]] = self.make_transition(*namestate) |
| names.append(namestate[0]) |
| return names, transitions |
| |
| def no_match(self, context, transitions): |
| """ |
| Called when there is no match from `StateMachine.check_line()`. |
| |
| Return the same values returned by transition methods: |
| |
| - context: unchanged; |
| - next state name: ``None``; |
| - empty result list. |
| |
| Override in subclasses to catch this event. |
| """ |
| return context, None, [] |
| |
| def bof(self, context): |
| """ |
| Handle beginning-of-file. Return unchanged `context`, empty result. |
| |
| Override in subclasses. |
| |
| Parameter `context`: application-defined storage. |
| """ |
| return context, [] |
| |
| def eof(self, context): |
| """ |
| Handle end-of-file. Return empty result. |
| |
| Override in subclasses. |
| |
| Parameter `context`: application-defined storage. |
| """ |
| return [] |
| |
| def nop(self, match, context, next_state): |
| """ |
| A "do nothing" transition method. |
| |
| Return unchanged `context` & `next_state`, empty result. Useful for |
| simple state changes (actionless transitions). |
| """ |
| return context, next_state, [] |
| |
| |
| class StateMachineWS(StateMachine): |
| |
| """ |
| `StateMachine` subclass specialized for whitespace recognition. |
| |
| There are three methods provided for extracting indented text blocks: |
| |
| - `get_indented()`: use when the indent is unknown. |
| - `get_known_indented()`: use when the indent is known for all lines. |
| - `get_first_known_indented()`: use when only the first line's indent is |
| known. |
| """ |
| |
| def get_indented(self, until_blank=0, strip_indent=1): |
| """ |
| Return a block of indented lines of text, and info. |
| |
| Extract an indented block where the indent is unknown for all lines. |
| |
| :Parameters: |
| - `until_blank`: Stop collecting at the first blank line if true |
| (1). |
| - `strip_indent`: Strip common leading indent if true (1, |
| default). |
| |
| :Return: |
| - the indented block (a list of lines of text), |
| - its indent, |
| - its first line offset from BOF, and |
| - whether or not it finished with a blank line. |
| """ |
| offset = self.abs_line_offset() |
| indented, indent, blank_finish = self.input_lines.get_indented( |
| self.line_offset, until_blank, strip_indent) |
| if indented: |
| self.next_line(len(indented) - 1) # advance to last indented line |
| while indented and not indented[0].strip(): |
| indented.trim_start() |
| offset += 1 |
| return indented, indent, offset, blank_finish |
| |
| def get_known_indented(self, indent, until_blank=0, strip_indent=1): |
| """ |
| Return an indented block and info. |
| |
| Extract an indented block where the indent is known for all lines. |
| Starting with the current line, extract the entire text block with at |
| least `indent` indentation (which must be whitespace, except for the |
| first line). |
| |
| :Parameters: |
| - `indent`: The number of indent columns/characters. |
| - `until_blank`: Stop collecting at the first blank line if true |
| (1). |
| - `strip_indent`: Strip `indent` characters of indentation if true |
| (1, default). |
| |
| :Return: |
| - the indented block, |
| - its first line offset from BOF, and |
| - whether or not it finished with a blank line. |
| """ |
| offset = self.abs_line_offset() |
| indented, indent, blank_finish = self.input_lines.get_indented( |
| self.line_offset, until_blank, strip_indent, |
| block_indent=indent) |
| self.next_line(len(indented) - 1) # advance to last indented line |
| while indented and not indented[0].strip(): |
| indented.trim_start() |
| offset += 1 |
| return indented, offset, blank_finish |
| |
| def get_first_known_indented(self, indent, until_blank=0, strip_indent=1, |
| strip_top=1): |
| """ |
| Return an indented block and info. |
| |
| Extract an indented block where the indent is known for the first line |
| and unknown for all other lines. |
| |
| :Parameters: |
| - `indent`: The first line's indent (# of columns/characters). |
| - `until_blank`: Stop collecting at the first blank line if true |
| (1). |
| - `strip_indent`: Strip `indent` characters of indentation if true |
| (1, default). |
| - `strip_top`: Strip blank lines from the beginning of the block. |
| |
| :Return: |
| - the indented block, |
| - its indent, |
| - its first line offset from BOF, and |
| - whether or not it finished with a blank line. |
| """ |
| offset = self.abs_line_offset() |
| indented, indent, blank_finish = self.input_lines.get_indented( |
| self.line_offset, until_blank, strip_indent, |
| first_indent=indent) |
| self.next_line(len(indented) - 1) # advance to last indented line |
| if strip_top: |
| while indented and not indented[0].strip(): |
| indented.trim_start() |
| offset += 1 |
| return indented, indent, offset, blank_finish |
| |
| |
| class StateWS(State): |
| |
| """ |
| State superclass specialized for whitespace (blank lines & indents). |
| |
| Use this class with `StateMachineWS`. The transitions 'blank' (for blank |
| lines) and 'indent' (for indented text blocks) are added automatically, |
| before any other transitions. The transition method `blank()` handles |
| blank lines and `indent()` handles nested indented blocks. Indented |
| blocks trigger a new state machine to be created by `indent()` and run. |
| The class of the state machine to be created is in `indent_sm`, and the |
| constructor keyword arguments are in the dictionary `indent_sm_kwargs`. |
| |
| The methods `known_indent()` and `firstknown_indent()` are provided for |
| indented blocks where the indent (all lines' and first line's only, |
| respectively) is known to the transition method, along with the attributes |
| `known_indent_sm` and `known_indent_sm_kwargs`. Neither transition method |
| is triggered automatically. |
| """ |
| |
| indent_sm = None |
| """ |
| The `StateMachine` class handling indented text blocks. |
| |
| If left as ``None``, `indent_sm` defaults to the value of |
| `State.nested_sm`. Override it in subclasses to avoid the default. |
| """ |
| |
| indent_sm_kwargs = None |
| """ |
| Keyword arguments dictionary, passed to the `indent_sm` constructor. |
| |
| If left as ``None``, `indent_sm_kwargs` defaults to the value of |
| `State.nested_sm_kwargs`. Override it in subclasses to avoid the default. |
| """ |
| |
| known_indent_sm = None |
| """ |
| The `StateMachine` class handling known-indented text blocks. |
| |
| If left as ``None``, `known_indent_sm` defaults to the value of |
| `indent_sm`. Override it in subclasses to avoid the default. |
| """ |
| |
| known_indent_sm_kwargs = None |
| """ |
| Keyword arguments dictionary, passed to the `known_indent_sm` constructor. |
| |
| If left as ``None``, `known_indent_sm_kwargs` defaults to the value of |
| `indent_sm_kwargs`. Override it in subclasses to avoid the default. |
| """ |
| |
| ws_patterns = {'blank': ' *$', |
| 'indent': ' +'} |
| """Patterns for default whitespace transitions. May be overridden in |
| subclasses.""" |
| |
| ws_initial_transitions = ('blank', 'indent') |
| """Default initial whitespace transitions, added before those listed in |
| `State.initial_transitions`. May be overridden in subclasses.""" |
| |
| def __init__(self, state_machine, debug=0): |
| """ |
| Initialize a `StateSM` object; extends `State.__init__()`. |
| |
| Check for indent state machine attributes, set defaults if not set. |
| """ |
| State.__init__(self, state_machine, debug) |
| if self.indent_sm is None: |
| self.indent_sm = self.nested_sm |
| if self.indent_sm_kwargs is None: |
| self.indent_sm_kwargs = self.nested_sm_kwargs |
| if self.known_indent_sm is None: |
| self.known_indent_sm = self.indent_sm |
| if self.known_indent_sm_kwargs is None: |
| self.known_indent_sm_kwargs = self.indent_sm_kwargs |
| |
| def add_initial_transitions(self): |
| """ |
| Add whitespace-specific transitions before those defined in subclass. |
| |
| Extends `State.add_initial_transitions()`. |
| """ |
| State.add_initial_transitions(self) |
| if self.patterns is None: |
| self.patterns = {} |
| self.patterns.update(self.ws_patterns) |
| names, transitions = self.make_transitions( |
| self.ws_initial_transitions) |
| self.add_transitions(names, transitions) |
| |
| def blank(self, match, context, next_state): |
| """Handle blank lines. Does nothing. Override in subclasses.""" |
| return self.nop(match, context, next_state) |
| |
| def indent(self, match, context, next_state): |
| """ |
| Handle an indented text block. Extend or override in subclasses. |
| |
| Recursively run the registered state machine for indented blocks |
| (`self.indent_sm`). |
| """ |
| indented, indent, line_offset, blank_finish = \ |
| self.state_machine.get_indented() |
| sm = self.indent_sm(debug=self.debug, **self.indent_sm_kwargs) |
| results = sm.run(indented, input_offset=line_offset) |
| return context, next_state, results |
| |
| def known_indent(self, match, context, next_state): |
| """ |
| Handle a known-indent text block. Extend or override in subclasses. |
| |
| Recursively run the registered state machine for known-indent indented |
| blocks (`self.known_indent_sm`). The indent is the length of the |
| match, ``match.end()``. |
| """ |
| indented, line_offset, blank_finish = \ |
| self.state_machine.get_known_indented(match.end()) |
| sm = self.known_indent_sm(debug=self.debug, |
| **self.known_indent_sm_kwargs) |
| results = sm.run(indented, input_offset=line_offset) |
| return context, next_state, results |
| |
| def first_known_indent(self, match, context, next_state): |
| """ |
| Handle an indented text block (first line's indent known). |
| |
| Extend or override in subclasses. |
| |
| Recursively run the registered state machine for known-indent indented |
| blocks (`self.known_indent_sm`). The indent is the length of the |
| match, ``match.end()``. |
| """ |
| indented, line_offset, blank_finish = \ |
| self.state_machine.get_first_known_indented(match.end()) |
| sm = self.known_indent_sm(debug=self.debug, |
| **self.known_indent_sm_kwargs) |
| results = sm.run(indented, input_offset=line_offset) |
| return context, next_state, results |
| |
| |
| class _SearchOverride: |
| |
| """ |
| Mix-in class to override `StateMachine` regular expression behavior. |
| |
| Changes regular expression matching, from the default `re.match()` |
| (succeeds only if the pattern matches at the start of `self.line`) to |
| `re.search()` (succeeds if the pattern matches anywhere in `self.line`). |
| When subclassing a `StateMachine`, list this class **first** in the |
| inheritance list of the class definition. |
| """ |
| |
| def match(self, pattern): |
| """ |
| Return the result of a regular expression search. |
| |
| Overrides `StateMachine.match()`. |
| |
| Parameter `pattern`: `re` compiled regular expression. |
| """ |
| return pattern.search(self.line) |
| |
| |
| class SearchStateMachine(_SearchOverride, StateMachine): |
| """`StateMachine` which uses `re.search()` instead of `re.match()`.""" |
| pass |
| |
| |
| class SearchStateMachineWS(_SearchOverride, StateMachineWS): |
| """`StateMachineWS` which uses `re.search()` instead of `re.match()`.""" |
| pass |
| |
| |
| class ViewList: |
| |
| """ |
| List with extended functionality: slices of ViewList objects are child |
| lists, linked to their parents. Changes made to a child list also affect |
| the parent list. A child list is effectively a "view" (in the SQL sense) |
| of the parent list. Changes to parent lists, however, do *not* affect |
| active child lists. If a parent list is changed, any active child lists |
| should be recreated. |
| |
| The start and end of the slice can be trimmed using the `trim_start()` and |
| `trim_end()` methods, without affecting the parent list. The link between |
| child and parent lists can be broken by calling `disconnect()` on the |
| child list. |
| |
| Also, ViewList objects keep track of the source & offset of each item. |
| This information is accessible via the `source()`, `offset()`, and |
| `info()` methods. |
| """ |
| |
| def __init__(self, initlist=None, source=None, items=None, |
| parent=None, parent_offset=None): |
| self.data = [] |
| """The actual list of data, flattened from various sources.""" |
| |
| self.items = [] |
| """A list of (source, offset) pairs, same length as `self.data`: the |
| source of each line and the offset of each line from the beginning of |
| its source.""" |
| |
| self.parent = parent |
| """The parent list.""" |
| |
| self.parent_offset = parent_offset |
| """Offset of this list from the beginning of the parent list.""" |
| |
| if isinstance(initlist, ViewList): |
| self.data = initlist.data[:] |
| self.items = initlist.items[:] |
| elif initlist is not None: |
| self.data = list(initlist) |
| if items: |
| self.items = items |
| else: |
| self.items = [(source, i) for i in range(len(initlist))] |
| assert len(self.data) == len(self.items), 'data mismatch' |
| |
| def __str__(self): |
| return str(self.data) |
| |
| def __repr__(self): |
| return '%s(%s, items=%s)' % (self.__class__.__name__, |
| self.data, self.items) |
| |
| def __lt__(self, other): return self.data < self.__cast(other) |
| def __le__(self, other): return self.data <= self.__cast(other) |
| def __eq__(self, other): return self.data == self.__cast(other) |
| def __ne__(self, other): return self.data != self.__cast(other) |
| def __gt__(self, other): return self.data > self.__cast(other) |
| def __ge__(self, other): return self.data >= self.__cast(other) |
| def __cmp__(self, other): return cmp(self.data, self.__cast(other)) |
| |
| def __cast(self, other): |
| if isinstance(other, ViewList): |
| return other.data |
| else: |
| return other |
| |
| def __contains__(self, item): return item in self.data |
| def __len__(self): return len(self.data) |
| |
| # The __getitem__()/__setitem__() methods check whether the index |
| # is a slice first, since indexing a native list with a slice object |
| # just works. |
| |
| def __getitem__(self, i): |
| if isinstance(i, types.SliceType): |
| assert i.step in (None, 1), 'cannot handle slice with stride' |
| return self.__class__(self.data[i.start:i.stop], |
| items=self.items[i.start:i.stop], |
| parent=self, parent_offset=i.start or 0) |
| else: |
| return self.data[i] |
| |
| def __setitem__(self, i, item): |
| if isinstance(i, types.SliceType): |
| assert i.step in (None, 1), 'cannot handle slice with stride' |
| if not isinstance(item, ViewList): |
| raise TypeError('assigning non-ViewList to ViewList slice') |
| self.data[i.start:i.stop] = item.data |
| self.items[i.start:i.stop] = item.items |
| assert len(self.data) == len(self.items), 'data mismatch' |
| if self.parent: |
| self.parent[(i.start or 0) + self.parent_offset |
| : (i.stop or len(self)) + self.parent_offset] = item |
| else: |
| self.data[i] = item |
| if self.parent: |
| self.parent[i + self.parent_offset] = item |
| |
| def __delitem__(self, i): |
| try: |
| del self.data[i] |
| del self.items[i] |
| if self.parent: |
| del self.parent[i + self.parent_offset] |
| except TypeError: |
| assert i.step is None, 'cannot handle slice with stride' |
| del self.data[i.start:i.stop] |
| del self.items[i.start:i.stop] |
| if self.parent: |
| del self.parent[(i.start or 0) + self.parent_offset |
| : (i.stop or len(self)) + self.parent_offset] |
| |
| def __add__(self, other): |
| if isinstance(other, ViewList): |
| return self.__class__(self.data + other.data, |
| items=(self.items + other.items)) |
| else: |
| raise TypeError('adding non-ViewList to a ViewList') |
| |
| def __radd__(self, other): |
| if isinstance(other, ViewList): |
| return self.__class__(other.data + self.data, |
| items=(other.items + self.items)) |
| else: |
| raise TypeError('adding ViewList to a non-ViewList') |
| |
| def __iadd__(self, other): |
| if isinstance(other, ViewList): |
| self.data += other.data |
| else: |
| raise TypeError('argument to += must be a ViewList') |
| return self |
| |
| def __mul__(self, n): |
| return self.__class__(self.data * n, items=(self.items * n)) |
| |
| __rmul__ = __mul__ |
| |
| def __imul__(self, n): |
| self.data *= n |
| self.items *= n |
| return self |
| |
| def extend(self, other): |
| if not isinstance(other, ViewList): |
| raise TypeError('extending a ViewList with a non-ViewList') |
| if self.parent: |
| self.parent.insert(len(self.data) + self.parent_offset, other) |
| self.data.extend(other.data) |
| self.items.extend(other.items) |
| |
| def append(self, item, source=None, offset=0): |
| if source is None: |
| self.extend(item) |
| else: |
| if self.parent: |
| self.parent.insert(len(self.data) + self.parent_offset, item, |
| source, offset) |
| self.data.append(item) |
| self.items.append((source, offset)) |
| |
| def insert(self, i, item, source=None, offset=0): |
| if source is None: |
| if not isinstance(item, ViewList): |
| raise TypeError('inserting non-ViewList with no source given') |
| self.data[i:i] = item.data |
| self.items[i:i] = item.items |
| if self.parent: |
| index = (len(self.data) + i) % len(self.data) |
| self.parent.insert(index + self.parent_offset, item) |
| else: |
| self.data.insert(i, item) |
| self.items.insert(i, (source, offset)) |
| if self.parent: |
| index = (len(self.data) + i) % len(self.data) |
| self.parent.insert(index + self.parent_offset, item, |
| source, offset) |
| |
| def pop(self, i=-1): |
| if self.parent: |
| index = (len(self.data) + i) % len(self.data) |
| self.parent.pop(index + self.parent_offset) |
| self.items.pop(i) |
| return self.data.pop(i) |
| |
| def trim_start(self, n=1): |
| """ |
| Remove items from the start of the list, without touching the parent. |
| """ |
| if n > len(self.data): |
| raise IndexError("Size of trim too large; can't trim %s items " |
| "from a list of size %s." % (n, len(self.data))) |
| elif n < 0: |
| raise IndexError('Trim size must be >= 0.') |
| del self.data[:n] |
| del self.items[:n] |
| if self.parent: |
| self.parent_offset += n |
| |
| def trim_end(self, n=1): |
| """ |
| Remove items from the end of the list, without touching the parent. |
| """ |
| if n > len(self.data): |
| raise IndexError("Size of trim too large; can't trim %s items " |
| "from a list of size %s." % (n, len(self.data))) |
| elif n < 0: |
| raise IndexError('Trim size must be >= 0.') |
| del self.data[-n:] |
| del self.items[-n:] |
| |
| def remove(self, item): |
| index = self.index(item) |
| del self[index] |
| |
| def count(self, item): return self.data.count(item) |
| def index(self, item): return self.data.index(item) |
| |
| def reverse(self): |
| self.data.reverse() |
| self.items.reverse() |
| self.parent = None |
| |
| def sort(self, *args): |
| tmp = zip(self.data, self.items) |
| tmp.sort(*args) |
| self.data = [entry[0] for entry in tmp] |
| self.items = [entry[1] for entry in tmp] |
| self.parent = None |
| |
| def info(self, i): |
| """Return source & offset for index `i`.""" |
| try: |
| return self.items[i] |
| except IndexError: |
| if i == len(self.data): # Just past the end |
| return self.items[i - 1][0], None |
| else: |
| raise |
| |
| def source(self, i): |
| """Return source for index `i`.""" |
| return self.info(i)[0] |
| |
| def offset(self, i): |
| """Return offset for index `i`.""" |
| return self.info(i)[1] |
| |
| def disconnect(self): |
| """Break link between this list and parent list.""" |
| self.parent = None |
| |
| def xitems(self): |
| """Return iterator yielding (source, offset, value) tuples.""" |
| for (value, (source, offset)) in zip(self.data, self.items): |
| yield (source, offset, value) |
| |
| def pprint(self): |
| """Print the list in `grep` format (`source:offset:value` lines)""" |
| for line in self.xitems(): |
| print "%s:%d:%s" % line |
| |
| |
| class StringList(ViewList): |
| |
| """A `ViewList` with string-specific methods.""" |
| |
| def trim_left(self, length, start=0, end=sys.maxint): |
| """ |
| Trim `length` characters off the beginning of each item, in-place, |
| from index `start` to `end`. No whitespace-checking is done on the |
| trimmed text. Does not affect slice parent. |
| """ |
| self.data[start:end] = [line[length:] |
| for line in self.data[start:end]] |
| |
| def get_text_block(self, start, flush_left=0): |
| """ |
| Return a contiguous block of text. |
| |
| If `flush_left` is true, raise `UnexpectedIndentationError` if an |
| indented line is encountered before the text block ends (with a blank |
| line). |
| """ |
| end = start |
| last = len(self.data) |
| while end < last: |
| line = self.data[end] |
| if not line.strip(): |
| break |
| if flush_left and (line[0] == ' '): |
| source, offset = self.info(end) |
| raise UnexpectedIndentationError(self[start:end], source, |
| offset + 1) |
| end += 1 |
| return self[start:end] |
| |
| def get_indented(self, start=0, until_blank=0, strip_indent=1, |
| block_indent=None, first_indent=None): |
| """ |
| Extract and return a StringList of indented lines of text. |
| |
| Collect all lines with indentation, determine the minimum indentation, |
| remove the minimum indentation from all indented lines (unless |
| `strip_indent` is false), and return them. All lines up to but not |
| including the first unindented line will be returned. |
| |
| :Parameters: |
| - `start`: The index of the first line to examine. |
| - `until_blank`: Stop collecting at the first blank line if true. |
| - `strip_indent`: Strip common leading indent if true (default). |
| - `block_indent`: The indent of the entire block, if known. |
| - `first_indent`: The indent of the first line, if known. |
| |
| :Return: |
| - a StringList of indented lines with mininum indent removed; |
| - the amount of the indent; |
| - a boolean: did the indented block finish with a blank line or EOF? |
| """ |
| indent = block_indent # start with None if unknown |
| end = start |
| if block_indent is not None and first_indent is None: |
| first_indent = block_indent |
| if first_indent is not None: |
| end += 1 |
| last = len(self.data) |
| while end < last: |
| line = self.data[end] |
| if line and (line[0] != ' ' |
| or (block_indent is not None |
| and line[:block_indent].strip())): |
| # Line not indented or insufficiently indented. |
| # Block finished properly iff the last indented line blank: |
| blank_finish = ((end > start) |
| and not self.data[end - 1].strip()) |
| break |
| stripped = line.lstrip() |
| if not stripped: # blank line |
| if until_blank: |
| blank_finish = 1 |
| break |
| elif block_indent is None: |
| line_indent = len(line) - len(stripped) |
| if indent is None: |
| indent = line_indent |
| else: |
| indent = min(indent, line_indent) |
| end += 1 |
| else: |
| blank_finish = 1 # block ends at end of lines |
| block = self[start:end] |
| if first_indent is not None and block: |
| block.data[0] = block.data[0][first_indent:] |
| if indent and strip_indent: |
| block.trim_left(indent, start=(first_indent is not None)) |
| return block, indent or 0, blank_finish |
| |
| def get_2D_block(self, top, left, bottom, right, strip_indent=1): |
| block = self[top:bottom] |
| indent = right |
| for i in range(len(block.data)): |
| block.data[i] = line = block.data[i][left:right].rstrip() |
| if line: |
| indent = min(indent, len(line) - len(line.lstrip())) |
| if strip_indent and 0 < indent < right: |
| block.data = [line[indent:] for line in block.data] |
| return block |
| |
| def pad_double_width(self, pad_char): |
| """ |
| Pad all double-width characters in self by appending `pad_char` to each. |
| For East Asian language support. |
| """ |
| if hasattr(unicodedata, 'east_asian_width'): |
| east_asian_width = unicodedata.east_asian_width |
| else: |
| return # new in Python 2.4 |
| for i in range(len(self.data)): |
| line = self.data[i] |
| if isinstance(line, unicode): |
| new = [] |
| for char in line: |
| new.append(char) |
| if east_asian_width(char) in 'WF': # 'W'ide & 'F'ull-width |
| new.append(pad_char) |
| self.data[i] = ''.join(new) |
| |
| def replace(self, old, new): |
| """Replace all occurrences of substring `old` with `new`.""" |
| for i in range(len(self.data)): |
| self.data[i] = self.data[i].replace(old, new) |
| |
| |
| class StateMachineError(Exception): pass |
| class UnknownStateError(StateMachineError): pass |
| class DuplicateStateError(StateMachineError): pass |
| class UnknownTransitionError(StateMachineError): pass |
| class DuplicateTransitionError(StateMachineError): pass |
| class TransitionPatternNotFound(StateMachineError): pass |
| class TransitionMethodNotFound(StateMachineError): pass |
| class UnexpectedIndentationError(StateMachineError): pass |
| |
| |
| class TransitionCorrection(Exception): |
| |
| """ |
| Raise from within a transition method to switch to another transition. |
| |
| Raise with one argument, the new transition name. |
| """ |
| |
| |
| class StateCorrection(Exception): |
| |
| """ |
| Raise from within a transition method to switch to another state. |
| |
| Raise with one or two arguments: new state name, and an optional new |
| transition name. |
| """ |
| |
| |
| def string2lines(astring, tab_width=8, convert_whitespace=0, |
| whitespace=re.compile('[\v\f]')): |
| """ |
| Return a list of one-line strings with tabs expanded, no newlines, and |
| trailing whitespace stripped. |
| |
| Each tab is expanded with between 1 and `tab_width` spaces, so that the |
| next character's index becomes a multiple of `tab_width` (8 by default). |
| |
| Parameters: |
| |
| - `astring`: a multi-line string. |
| - `tab_width`: the number of columns between tab stops. |
| - `convert_whitespace`: convert form feeds and vertical tabs to spaces? |
| """ |
| if convert_whitespace: |
| astring = whitespace.sub(' ', astring) |
| return [s.expandtabs(tab_width).rstrip() for s in astring.splitlines()] |
| |
| def _exception_data(): |
| """ |
| Return exception information: |
| |
| - the exception's class name; |
| - the exception object; |
| - the name of the file containing the offending code; |
| - the line number of the offending code; |
| - the function name of the offending code. |
| """ |
| type, value, traceback = sys.exc_info() |
| while traceback.tb_next: |
| traceback = traceback.tb_next |
| code = traceback.tb_frame.f_code |
| return (type.__name__, value, code.co_filename, traceback.tb_lineno, |
| code.co_name) |
