# taskflow.patterns.linear_flow

# Source code for taskflow.patterns.linear_flow

    # -*- coding: utf-8 -*-

    #    Copyright (C) 2012 Yahoo! Inc. All Rights Reserved.
    #
    #    Licensed under the Apache License, Version 2.0 (the "License"); you may
    #    not use this file except in compliance with the License. You may obtain
    #    a copy of the License at
    #
    #         http://www.apache.org/licenses/LICENSE-2.0
    #
    #    Unless required by applicable law or agreed to in writing, software
    #    distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
    #    WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
    #    License for the specific language governing permissions and limitations
    #    under the License.

    from taskflow import flow
    from taskflow.types import graph as gr

    class Flow(flow.Flow):
        """Linear flow pattern.

        A linear (potentially nested) flow of *tasks/flows* that can be
        applied in order as one unit and rolled back as one unit using
        the reverse order that the *tasks/flows* have been applied in.
        """

        _no_last_item = object()
        """Sentinel object used to denote no last item has been assigned.

        This is used to track no last item being added, since at creation there
        is no last item, but since the :meth:`.add` routine can take any object
        including none, we have to use a different object to be able to
        distinguish the lack of any last item...
        """

        def __init__(self, name, retry=None):
            super(Flow, self).__init__(name, retry)
            self._graph = gr.OrderedDiGraph(name=name)
            self._last_item = self._no_last_item

        def add(self, *items):
            """Adds a given task/tasks/flow/flows to this flow."""
            for item in items:
                if not self._graph.has_node(item):
                    self._graph.add_node(item)
                    if self._last_item is not self._no_last_item:
                        self._graph.add_edge(self._last_item, item,
                                             attr_dict={flow.LINK_INVARIANT: True})
                    self._last_item = item
            return self

        def __len__(self):
            return len(self._graph)

        def __iter__(self):
            for item in self._graph.nodes:
                yield item

        @property
        def requires(self):
            requires = set()
            prior_provides = set()
            if self._retry is not None:
                requires.update(self._retry.requires)
                prior_provides.update(self._retry.provides)
            for item in self:
                requires.update(item.requires - prior_provides)
                prior_provides.update(item.provides)
            return frozenset(requires)

        def iter_nodes(self):
            for (n, n_data) in self._graph.nodes(data=True):
                yield (n, n_data)

        def iter_links(self):
            for (u, v, e_data) in self._graph.edges(data=True):
                yield (u, v, e_data)

this page last updated: 2022-03-02 20:51:50

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