napari.qt.threading

Classes

FunctionWorker	QRunnable with signals that wraps a simple long-running function.
GeneratorWorker	QRunnable with signals that wraps a long-running generator.
GeneratorWorkerSignals
WorkerBase	Base class for creating a Worker that can run in another thread.
WorkerBaseSignals

Functions

napari.qt.threading.active_thread_count()

Return the number of active threads in the global ThreadPool.

Return type

int

napari.qt.threading.create_worker(func, *args, _start_thread=None, _connect=None, _worker_class=None, _ignore_errors=False, **kwargs)

Convenience function to start a function in another thread.

By default, uses Worker, but a custom WorkerBase subclass may be provided. If so, it must be a subclass of Worker, which defines a standard set of signals and a run method.

Parameters

• func (Callable) – The function to call in another thread.

• _start_thread (bool, optional) – Whether to immediaetly start the thread. If False, the returned worker must be manually started with worker.start(). by default it will be False if the _connect argument is None, otherwise True.

• _connect (Dict[str, Union[Callable, Sequence]], optional) – A mapping of "signal_name" -> callable or list of callable: callback functions to connect to the various signals offered by the worker class. by default None

• _worker_class (Type[WorkerBase], optional) – The :class`WorkerBase` to instantiate, by default FunctionWorker will be used if func is a regular function, and GeneratorWorker will be used if it is a generator.

• _ignore_errors (bool, optional) – If False (the default), errors raised in the other thread will be reraised in the main thread (makes debugging significantly easier).

• *args – will be passed to func

• **kwargs – will be passed to func

Returns

worker – An instantiated worker. If _start_thread was False, the worker will have a .start() method that can be used to start the thread.

Return type

WorkerBase

Raises

• TypeError – If a worker_class is provided that is not a subclass of WorkerBase.

• TypeError – If _connect is provided and is not a dict of {str: callable}

Examples

def long_function(duration):
    import time
    time.sleep(duration)

worker = create_worker(long_function, 10)

napari.qt.threading.set_max_thread_count(num)

Set the maximum number of threads used by the thread pool.

Note: The thread pool will always use at least 1 thread, even if maxThreadCount limit is zero or negative.