pyrseus.executors.cpnocatch.CpNoCatchExecutor

class pyrseus.executors.cpnocatch.CpNoCatchExecutor

Bases: NoCatchExecutor

Pickle-testing variant of NoCatchExecutor, using the 3rd party cloudpickle module.

Summary

• Common Use Cases: for troubleshooting with extra cloudpickle testing, as a fail-fast variant of CpInlineExecutor.

• Concurrency: This is a non-concurrent, serial-only executor. All tasks are immediately run in the same process and thread they were submitted in.

• Exceptions: This executor has non-standard exception-handling semantics: no task exceptions are caught and captured in their futures. Exceptions are propagated out immediately.

• Default max_workers: Not applicable.

• Pickling: This executor takes extra time to pickle and unpickle all tasks and their results. If you aren’t troubleshooting such issues and prefer lower overhead, consider using NoCatchExecutor instead.

Details

This executor pickles each submitted task and the task’s results, using the built-in cloudpickle module that understands things like lambdas. This is primarily useful for troubleshooting pickling problems occurring in multi-process executors, by performing the pickling and unpickling locally.

Consider this lambda.

>>> import pickle
>>> needs_cloudpickle = lambda: "this works if using cloudpickle for pickling"

It can’t be pickled with pickle.

>>> pickle.dumps(needs_cloudpickle, -1)
Traceback (most recent call last):
...
_pickle.PicklingError: Can't pickle ...

But it can be pickled with cloudpickle.

>>> print(pickle.loads(cloudpickle.dumps(needs_cloudpickle, -1))())
this works if using cloudpickle for pickling

Since this class uses cloudpickle for pickling, it works fine.

>>> with CpNoCatchExecutor() as exe:
...     fut = exe.submit(needs_cloudpickle)
...     print(fut.result())
this works if using cloudpickle for pickling

See Pyrseus’ Executor Classes for a list of related executors.

__init__()

A simple serial Executor that evaluates tasks immediately upon submission, and does not capture task exceptions in their futures.

Summary

• Common Use Cases: for troubleshooting, as a fail-fast variant of the InlineExecutor.

• Concurrency: This is a non-concurrent, serial-only executor. All tasks are immediately run in the same process and thread they were submitted in.

• Exceptions: This executor has non-standard exception-handling semantics: no task exceptions are caught and captured in their futures. Exceptions are propagated out immediately.

• Default max_workers: Not applicable.

• Pickling: This executor does not perform any pickling.

Details

This is primarily useful for troubleshooting when one wants to enter a debugger as early and as easily as possible, at the cost of non-standard error handling.

Consider the following function that raises an exception:

>>> def raises():
...     raise RuntimeError("An exception was raised by our function.")

With this class, the exception is propagated out immediately at submit time.

>>> with NoCatchExecutor() as exe:
...     exe.submit(raises)  # <--- NOTE: no fut.result() needed
Traceback (most recent call last):
...
RuntimeError: An exception was raised by our function.

See Pyrseus’ Executor Classes for a list of related executors.

Methods

__init__()	A simple serial Executor that evaluates tasks immediately upon submission, and does not capture task exceptions in their futures.
map(fn, *iterables[, timeout, chunksize])	Returns an iterator equivalent to map(fn, iter).
shutdown(*args, **kwargs)	As a minor improvement on the base class' method, this override disallows submissions after a shutdown has been started.
submit(fcn, /, *args, **kwargs)	Immediately evaluates fcn(*args, **kwargs) and embeds the result in a Future.

__enter__()

__exit__(exc_type, exc_val, exc_tb)

map(fn, *iterables, timeout=None, chunksize=1)

Returns an iterator equivalent to map(fn, iter).

Parameters:

• fn – A callable that will take as many arguments as there are passed iterables.

• timeout – The maximum number of seconds to wait. If None, then there is no limit on the wait time.

• chunksize – The size of the chunks the iterable will be broken into before being passed to a child process. This argument is only used by ProcessPoolExecutor; it is ignored by ThreadPoolExecutor.

Returns:

map(func, *iterables) but the calls may be evaluated out-of-order.

Return type:

An iterator equivalent to

Raises:

• TimeoutError – If the entire result iterator could not be generated before the given timeout.

• Exception – If fn(*args) raises for any values.

shutdown(*args, **kwargs)

As a minor improvement on the base class’ method, this override disallows submissions after a shutdown has been started. This can assist with finding bugs in user code.

submit(fcn, /, *args, **kwargs)

Immediately evaluates fcn(*args, **kwargs) and embeds the result in a Future. Unlike with standard executors, this method does not capture exceptions. They are propagated out immediately.