Python Document Workflows
An implementation of document workflows in Python. Designed for SQLAlchemy but not dependent upon it.
Note: This is currently just a planning document.
Define your document the usual way (SQLAlchemy example):
Base = base_metadata() # SQLAlchemy base class class MyDocument(Base): status = Column(Integer) email = Column(Unicode(250)) email_verified = Column(Boolean, default=False) ...
Define a workflow for this document type:
from docflow import DocumentWorkflow, WorkflowState, WorkflowStateGroup, WorkflowTransition from docflow import TransitionException class MyDocumentWorkflow(DocumentWorkflow): """ Workflow for MyDocument """ # Attribute in MyDocument to store status in. # Use ``state_key`` if MyDocument is a dictionary, # as is typical with NoSQL JSON-based databases. state_attr = 'status' # Define a state. First parameter is the state tracking value, # stored in status_attr draft = WorkflowState(0, default=True, title="Draft", description="Only owner can see it") pending = WorkflowState(1, title="Pending", description="Pending review") published = WorkflowState(2, title="Published", description="Published") withdrawn = WorkflowState(3, title="Withdrawn", description="Withdrawn by owner") rejected = WorkflowState(4, title="Rejected", description="Rejected by reviewer") # Define a state group not_published = WorkflowStateGroup([0, 1], title="Not Published") def permissions(self, context=None): """ Return permissions available to current user. A permission can be any hashable token. """ if context and context['is_admin']: return ['can_publish'] else: return  # Define a transition. There can be multiple transitions connecting any two states, with # differing conditions on their use. Parameters: old, new, permission, title, description # The state names (as strings) must match the variable names above. @WorkflowTransition('draft', 'pending', None, title="Submit") def submit(self, context=None): """ Change workflow state from draft to pending. """ # Do something here # ... # Internal API call to set the state flag self._setState(self.pending) @WorkflowTransition('pending', 'published', 'can_publish', title="Publish") def publish(self, context=None): """ Publish the document. """ # Also do something here if not self.document.email_verified: raise TransitionException("Email address is not verified.") self._setState(self.published) # Apply workflow to document >>> doc = MyDocument() >>> wf = MyDocumentWorkflow(doc) >>> wf.draft() True >>> wf.pending() False >>> wf.not_published() True >>> wf.state <WorkflowState "Draft"> >>> wf.all_states() # All states [<WorkflowState "Draft">, <WorkflowState "Pending">, <WorkflowState "Published">, <WorkflowState "Withdrawn">, <WorkflowState "Rejected">] >>> wf.transitions(context=None) # Available transitions [<WorkflowTransition "Submit">] >>> wf.submit() # Perform a transition >>> wf.state <WorkflowState "Pending">