Source code for panel.pipeline

import sys
import traceback as tb

from collections import OrderedDict, defaultdict

import param

from .layout import Column, Row
from .pane import HoloViews, Markdown
from .param import Param
from .util import param_reprs
from .viewable import Viewer
from .widgets import Button, Select


class PipelineError(RuntimeError):
    """
    Custom error type which can be raised to display custom error
    message in a Pipeline.
    """


def traverse(graph, v, visited):
    """
    Traverse the graph from a node and mark visited vertices.
    """
    visited[v] = True
    # Recur for all the vertices adjacent to this vertex
    for i in graph.get(v, []):
        if visited[i] == False:
            traverse(graph, i, visited)


def find_route(graph, current, target):
    """
    Find a route to the target node from the current node.
    """
    next_nodes = graph.get(current)
    if next_nodes is None:
        return None
    elif target in next_nodes:
        return [target]
    else:
        for n in next_nodes:
            route = find_route(graph, n, target)
            if route is None:
                continue
            return [n]+route
        return None


def get_root(graph):
    """
    Search for the root node by finding nodes without inputs.
    """
    # Find root node
    roots = []
    targets = [t for ts in graph.values() for t in ts]
    for src in graph:
        if src not in targets:
            roots.append(src)

    if len(roots) > 1:
        raise ValueError("Graph has more than one node with no "
                         "incoming edges. Ensure that the graph "
                         "only has a single source node.")
    elif len(roots) == 0:
        raise ValueError("Graph has no source node. Ensure that the "
                         "graph is not cyclic and has a single "
                         "starting point.")
    return roots[0]


def is_traversable(root, graph, stages):
    """
    Check if the graph is fully traversable from the root node.
    """
    # Ensure graph is traverable from root
    int_graph = {stages.index(s): tuple(stages.index(t) for t in tgts)
                 for s, tgts in graph.items()}
    visited = [False]*len(stages)
    traverse(int_graph, stages.index(root), visited)
    return all(visited)


def get_depth(node, graph, depth=0):
    depths = []
    for sub in graph.get(node, []):
        depths.append(get_depth(sub, graph, depth+1))
    return max(depths) if depths else depth+1


def get_breadths(node, graph, depth=0, breadths=None):
    if breadths is None:
        breadths = defaultdict(list)
        breadths[depth].append(node)
    for sub in graph.get(node, []):
        if sub not in breadths[depth+1]:
            breadths[depth+1].append(sub)
        get_breadths(sub, graph, depth+1, breadths)
    return breadths



[docs]class Pipeline(Viewer): """ A Pipeline represents a directed graph of stages, which each return a panel object to render. A pipeline therefore represents a UI workflow of multiple linear or branching stages. The Pipeline layout consists of a number of sub-components: * header: * title: The name of the current stage. * error: A field to display the error state. * network: A network diagram representing the pipeline. * buttons: All navigation buttons and selectors. * prev_button: The button to go to the previous stage. * prev_selector: The selector widget to select between previous branching stages. * next_button: The button to go to the previous stage * next_selector: The selector widget to select the next branching stages. * stage: The contents of the current pipeline stage. By default any outputs of one stage annotated with the param.output decorator are fed into the next stage. Additionally, if the inherit_params parameter is set any parameters which are declared on both the previous and next stage are also inherited. The stages are declared using the add_stage method and must each be given a unique name. By default any stages will simply be connected linearly, but an explicit graph can be declared using the define_graph method. """ auto_advance = param.Boolean(default=False, doc=""" Whether to automatically advance if the ready parameter is True.""") debug = param.Boolean(default=False, doc=""" Whether to raise errors, useful for debugging while building an application.""") inherit_params = param.Boolean(default=True, doc=""" Whether parameters should be inherited between pipeline stages.""") next_parameter = param.String(default=None, doc=""" Parameter name to watch to switch between different branching stages""") ready_parameter = param.String(default=None, doc=""" Parameter name to watch to check whether a stage is ready.""") show_header = param.Boolean(default=True, doc=""" Whether to show the header with the title, network diagram, and buttons.""") next = param.Action(default=lambda x: x.param.trigger('next')) previous = param.Action(default=lambda x: x.param.trigger('previous')) def __init__(self, stages=[], graph={}, **params): try: import holoviews as hv except Exception: raise ImportError('Pipeline requires holoviews to be installed') super().__init__(**params) # Initialize internal state self._stage = None self._stages = OrderedDict() self._states = {} self._state = None self._linear = True self._block = False self._error = None self._graph = {} self._route = [] # Declare UI components self._progress_sel = hv.streams.Selection1D() self._progress_sel.add_subscriber(self._set_stage) self.prev_button = Param(self.param.previous).layout[0] self.prev_button.width = 125 self.prev_selector = Select(width=125) self.next_button = Param(self.param.next).layout[0] self.next_button.width = 125 self.next_selector = Select(width=125) self.prev_button.disabled = True self.next_selector.param.watch(self._update_progress, 'value') self.network = HoloViews(backend='bokeh') self.title = Markdown('# Header', margin=(0, 0, 0, 5)) self.error = Row(width=100) self.buttons = Row(self.prev_button, self.next_button) self.header = Row( Column(self.title, self.error), self.network, self.buttons, sizing_mode='stretch_width' ) self.network.object = self._make_progress() self.stage = Row() self.layout = Column(self.header, self.stage, sizing_mode='stretch_width') # Initialize stages and the graph for stage in stages: kwargs = {} if len(stage) == 2: name, stage = stage elif len(stage) == 3: name, stage, kwargs = stage self.add_stage(name, stage, **kwargs) self.define_graph(graph) def __panel__(self): return self.layout def _validate(self, stage): if any(stage is s for n, (s, kw) in self._stages.items()): raise ValueError('Stage %s is already in pipeline' % stage) elif not ((isinstance(stage, type) and issubclass(stage, param.Parameterized)) or isinstance(stage, param.Parameterized)): raise ValueError('Pipeline stages must be Parameterized classes or instances.') def __repr__(self): repr_str = 'Pipeline:' for i, (name, (stage, _)) in enumerate(self._stages.items()): if isinstance(stage, param.Parameterized): cls_name = type(stage).__name__ else: cls_name = stage.__name__ params = ', '.join(param_reprs(stage)) repr_str += '\n [%d] %s: %s(%s)' % (i, name, cls_name, params) return repr_str def __str__(self): return self.__repr__() def __getitem__(self, index): return self._stages[index][0] def _unblock(self, event): if self._state is not event.obj or self._block: self._block = False return button = self.next_button if button.disabled and event.new: button.disabled = False elif not button.disabled and not event.new: button.disabled = True stage_kwargs = self._stages[self._stage][-1] if event.new and stage_kwargs.get('auto_advance', self.auto_advance): self._next() def _select_next(self, event): if self._state is not event.obj: return self.next_selector.value = event.new self._update_progress() def _init_stage(self): stage, stage_kwargs = self._stages[self._stage] previous = [] for src, tgts in self._graph.items(): if self._stage in tgts: previous.append(src) prev_states = [self._states[prev] for prev in previous if prev in self._states] outputs = [] kwargs, results = {}, {} for state in prev_states: for name, (_, method, index) in state.param.outputs().items(): if name not in stage.param: continue if method not in results: results[method] = method() result = results[method] if index is not None: result = result[index] kwargs[name] = result outputs.append(name) if stage_kwargs.get('inherit_params', self.inherit_params): ignored = [stage_kwargs.get(p) or getattr(self, p, None) for p in ('ready_parameter', 'next_parameter')] params = [k for k, v in state.param.objects('existing').items() if k not in ignored] kwargs.update({k: v for k, v in state.param.values().items() if k in stage.param and k != 'name' and k in params}) if isinstance(stage, param.Parameterized): stage.param.update(**kwargs) self._state = stage else: self._state = stage(**kwargs) # Hide widgets for parameters that are supplied by the previous stage for output in outputs: self._state.param[output].precedence = -1 ready_param = stage_kwargs.get('ready_parameter', self.ready_parameter) if ready_param and ready_param in stage.param: self._state.param.watch(self._unblock, ready_param, onlychanged=False) next_param = stage_kwargs.get('next_parameter', self.next_parameter) if next_param and next_param in stage.param: self._state.param.watch(self._select_next, next_param, onlychanged=False) self._states[self._stage] = self._state return self._state.panel() def _set_stage(self, index): if not index: return stage = self._progress_sel.source.iloc[index[0], 2] if stage in self.next_selector.options: self.next_selector.value = stage self.param.trigger('next') elif stage in self.prev_selector.options: self.prev_selector.value = stage self.param.trigger('previous') elif stage in self._route: while len(self._route) > 1: self.param.trigger('previous') else: # Try currently selected route route = find_route(self._graph, self._next_stage, stage) if route is None: # Try alternate route route = find_route(self._graph, self._stage, stage) if route is None: raise ValueError('Could not find route to target node.') else: route = [self._next_stage] + route for r in route: if r not in self.next_selector.options: break self.next_selector.value = r self.param.trigger('next') @property def _next_stage(self): return self.next_selector.value @property def _prev_stage(self): return self.prev_selector.value def _update_button(self): stage, kwargs = self._stages[self._stage] options = list(self._graph.get(self._stage, [])) next_param = kwargs.get('next_parameter', self.next_parameter) option = getattr(self._state, next_param) if next_param and next_param in stage.param else None if option is None: option = options[0] if options else None self.next_selector.options = options self.next_selector.value = option self.next_selector.disabled = not bool(options) previous = [] for src, tgts in self._graph.items(): if self._stage in tgts: previous.append(src) self.prev_selector.options = previous self.prev_selector.value = self._route[-1] if previous else None self.prev_selector.disabled = not bool(previous) # Disable previous button if self._prev_stage is None: self.prev_button.disabled = True else: self.prev_button.disabled = False # Disable next button if self._next_stage is None: self.next_button.disabled = True else: ready = kwargs.get('ready_parameter', self.ready_parameter) disabled = (not getattr(stage, ready)) if ready in stage.param else False self.next_button.disabled = disabled def _get_error_button(self, e): msg = str(e) if isinstance(e, PipelineError) else "" if self.debug: type, value, trb = sys.exc_info() tb_list = tb.format_tb(trb, None) + tb.format_exception_only(type, value) traceback = (("%s\n\nTraceback (innermost last):\n" + "%-20s %s") % (msg, ''.join(tb_list[-5:-1]), tb_list[-1])) else: traceback = msg or "Undefined error, enable debug mode." button = Button(name='Error', button_type='danger', width=100, align='center', margin=(0, 0, 0, 5)) button.js_on_click(code="alert(`{tb}`)".format(tb=traceback)) return button @param.depends('next', watch=True) def _next(self): prev_state, prev_stage = self._state, self._stage self._stage = self._next_stage self.stage.loading = True try: self.stage[0] = self._init_stage() except Exception as e: self._error = self._stage self._stage = prev_stage self._state = prev_state self.stage[0] = prev_state.panel() self.error[:] = [self._get_error_button(e)] if self.debug: raise e return e else: self.error[:] = [] self._error = None self._update_button() self._route.append(self._stage) stage_kwargs = self._stages[self._stage][-1] ready_param = stage_kwargs.get('ready_parameter', self.ready_parameter) if (ready_param and getattr(self._state, ready_param, False) and stage_kwargs.get('auto_advance', self.auto_advance)): self._next() finally: self._update_progress() self.stage.loading = False @param.depends('previous', watch=True) def _previous(self): prev_state, prev_stage = self._state, self._stage self._stage = self._prev_stage try: if self._stage in self._states: self._state = self._states[self._stage] self.stage[0] = self._state.panel() else: self.stage[0] = self._init_stage() self._block = True except Exception as e: self.error[:] = [self._get_error_button(e)] self._error = self._stage self._stage = prev_stage self._state = prev_state if self.debug: raise e else: self.error[:] = [] self._error = None self._update_button() self._route.pop() finally: self._update_progress() def _update_progress(self, *args): self.title.object = '## Stage: ' + self._stage self.network.object = self._make_progress() def _make_progress(self): import holoviews as hv import holoviews.plotting.bokeh # noqa if self._graph: root = get_root(self._graph) depth = get_depth(root, self._graph) breadths = get_breadths(root, self._graph) max_breadth = max(len(v) for v in breadths.values()) else: root = None max_breadth, depth = 0, 0 breadths = {} height = 80 + (max_breadth-1) * 20 edges = [] for src, tgts in self._graph.items(): for t in tgts: edges.append((src, t)) nodes = [] for depth, subnodes in breadths.items(): breadth = len(subnodes) step = 1./breadth for i, n in enumerate(subnodes[::-1]): if n == self._stage: state = 'active' elif n == self._error: state = 'error' elif n == self._next_stage: state = 'next' else: state = 'inactive' nodes.append((depth, step/2.+i*step, n, state)) cmap = {'inactive': 'white', 'active': '#5cb85c', 'error': 'red', 'next': 'yellow'} def tap_renderer(plot, element): from bokeh.models import TapTool gr = plot.handles['glyph_renderer'] tap = plot.state.select_one(TapTool) tap.renderers = [gr] nodes = hv.Nodes(nodes, ['x', 'y', 'Stage'], 'State').opts( alpha=0, default_tools=['tap'], hooks=[tap_renderer], hover_alpha=0, selection_alpha=0, nonselection_alpha=0, axiswise=True, size=10, backend='bokeh' ) self._progress_sel.source = nodes graph = hv.Graph((edges, nodes)).opts( edge_hover_line_color='black', node_color='State', cmap=cmap, tools=[], default_tools=['hover'], selection_policy=None, node_hover_fill_color='gray', axiswise=True, backend='bokeh') labels = hv.Labels(nodes, ['x', 'y'], 'Stage').opts( yoffset=-.30, default_tools=[], axiswise=True, backend='bokeh' ) plot = (graph * labels * nodes) if self._linear else (graph * nodes) plot.opts( xaxis=None, yaxis=None, min_width=400, responsive=True, show_frame=False, height=height, xlim=(-0.25, depth+0.25), ylim=(0, 1), default_tools=['hover'], toolbar=None, backend='bokeh' ) return plot #---------------------------------------------------------------- # Public API #----------------------------------------------------------------
[docs] def add_stage(self, name, stage, **kwargs): """ Adds a new, named stage to the Pipeline. Arguments --------- name: str A string name for the Pipeline stage stage: param.Parameterized A Parameterized object which represents the Pipeline stage. **kwargs: dict Additional arguments declaring the behavior of the stage. """ self._validate(stage) for k in kwargs: if k not in self.param: raise ValueError("Keyword argument %s is not a valid parameter. " % k) if not self._linear and self._graph: raise RuntimeError("Cannot add stage after graph has been defined.") self._stages[name] = (stage, kwargs) if len(self._stages) == 1: self._stage = name self._route = [name] self._graph = {} self.stage[:] = [self._init_stage()] else: previous = [s for s in self._stages if s not in self._graph][0] self._graph[previous] = (name,) self._update_progress() self._update_button()
[docs] def define_graph(self, graph, force=False): """ Declares a custom graph structure for the Pipeline overriding the default linear flow. The graph should be defined as an adjacency mapping. Arguments --------- graph: dict Dictionary declaring the relationship between different pipeline stages. Should map from a single stage name to one or more stage names. """ stages = list(self._stages) if not stages: self._graph = {} return graph = {k: v if isinstance(v, tuple) else (v,) for k, v in graph.items()} not_found = [] for source, targets in graph.items(): if source not in stages: not_found.append(source) not_found += [t for t in targets if t not in stages] if not_found: raise ValueError( 'Pipeline stage(s) %s not found, ensure all stages ' 'referenced in the graph have been added.' % (not_found[0] if len(not_found) == 1 else not_found) ) if graph: if not (self._linear or force): raise ValueError("Graph has already been defined, " "cannot override existing graph.") self._linear = False else: graph = {s: (t,) for s, t in zip(stages[:-1], stages[1:])} root = get_root(graph) if not is_traversable(root, graph, stages): raise ValueError('Graph is not fully traversable from stage: %s.' % root) reinit = root is not self._stage self._stage = root self._graph = graph self._route = [root] if not self._linear: self.buttons[:] = [ Column(self.prev_selector, self.prev_button), Column(self.next_selector, self.next_button) ] if reinit: self.stage[:] = [self._init_stage()] self._update_progress() self._update_button()
__all__ = ( "Pipeline", )