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raise TypeError('Task function must be a callable object')
if (len(task['outputs']) > 1 and
not inspect.isgeneratorfunction(task['fn'])):
raise TypeError('Multiple outputs are only supported with \
generator functions')
if inspect.isgeneratorfunction(task['fn']):
if task['outputs'][0] == '*':
raise TypeError('Generator functions cannot be used for tasks with \
output specification "*"')
return Task(**task)
def input_parser(key, data):
"""Used to pass in full workspace if an input is defined as '*'"""
if key == '*':
return copy.copy(data)
else:
return data[key]
def run_task(task, workspace):
"""
Runs the task and updates the workspace with results.
Parameters
----------
task - dict
Task Description
Examples:
{'task': task_func, 'inputs': ['a', 'b'], 'outputs': 'c'}
{'task': task_func, 'inputs': '*', 'outputs': '*'}
{'task': task_func, 'inputs': ['*','a'], 'outputs': 'b'}
Returns a new workspace with results
"""
data = copy.copy(workspace)
task = validate_task(task)
# Prepare input to task
inputs = [input_parser(key, data) for key in task.inputs]
if inspect.isgeneratorfunction(task.fn):
# Multiple output task
# Assuming number of outputs are equal to number of return values
data.update(zip(task.outputs, task.fn(*inputs)))
else:
# Single output task
results = task.fn(*inputs)
if task.outputs[0] != '*':
results = {task.outputs[0]: results}
elif not isinstance(results, dict):
raise TypeError('Result should be a dict for output type *')
data.update(results)
return data
def run_hook(name, workspace, hooks):
"""Runs all hooks added under the give name.
Parameters
----------
name - str
Name of the hook to invoke
workspace - dict
Workspace that the hook functions operate on
hooks - dict of lists
Mapping with hook names and callback functions
"""
data = copy.copy(workspace)
for hook_listener in hooks.get(name, []):
# Hook functions may mutate the data and returns nothing
hook_listener(data)
return data
Task = collections.namedtuple('Task', ['fn', 'inputs', 'outputs'])
Hook = str # For now
class Workflow(object):
def __init__(self, task_list=None, description='simplepipe Workflow'):
if task_list is None:
self.tasks = []
else:
self.tasks = task_list
self.hooks = {}
self.__doc__ = description
def add_task(self, fn, inputs=None, outputs=None):
"""
Adds a task to the workflow.