from __future__ import annotations
import inspect
import time
import warnings
from functools import partial, wraps
from typing import (
TYPE_CHECKING,
Any,
Callable,
Generator,
Generic,
Sequence,
TypeVar,
overload,
)
from qtpy.QtCore import QObject, QRunnable, QThread, QThreadPool, QTimer, Signal
if TYPE_CHECKING:
_T = TypeVar("_T")
class SigInst(Generic[_T]):
@staticmethod
def connect(slot: Callable[[_T], Any], type: type | None = ...) -> None:
...
@staticmethod
def disconnect(slot: Callable[[_T], Any] = ...) -> None:
...
@staticmethod
def emit(*args: _T) -> None:
...
from typing_extensions import Literal, ParamSpec
_P = ParamSpec("_P")
# maintain runtime compatibility with older typing_extensions
else:
try:
from typing_extensions import ParamSpec
_P = ParamSpec("_P")
except ImportError:
_P = TypeVar("_P")
_Y = TypeVar("_Y")
_S = TypeVar("_S")
_R = TypeVar("_R")
def as_generator_function(
func: Callable[_P, _R]
) -> Callable[_P, Generator[None, None, _R]]:
"""Turns a regular function (single return) into a generator function."""
@wraps(func)
def genwrapper(*args: Any, **kwargs: Any) -> Generator[None, None, _R]:
yield
return func(*args, **kwargs)
return genwrapper
[docs]class WorkerBaseSignals(QObject):
started = Signal() # emitted when the work is started
finished = Signal() # emitted when the work is finished
_finished = Signal(object) # emitted when the work is finished ro delete
returned = Signal(object) # emitted with return value
errored = Signal(object) # emitted with error object on Exception
warned = Signal(tuple) # emitted with showwarning args on warning
[docs]class WorkerBase(QRunnable, Generic[_R]):
"""Base class for creating a Worker that can run in another thread.
Parameters
----------
SignalsClass : type, optional
A QObject subclass that contains signals, by default WorkerBaseSignals
Attributes
----------
signals: WorkerBaseSignals
signal emitter object. To allow identify which worker thread emitted signal.
"""
#: A set of Workers. Add to set using `WorkerBase.start`
_worker_set: set[WorkerBase] = set()
returned: SigInst[_R]
errored: SigInst[Exception]
warned: SigInst[tuple]
started: SigInst[None]
finished: SigInst[None]
def __init__(
self,
func: Callable[_P, _R] | None = None,
SignalsClass: type[WorkerBaseSignals] = WorkerBaseSignals,
) -> None:
super().__init__()
self._abort_requested = False
self._running = False
self.signals = SignalsClass()
def __getattr__(self, name: str) -> SigInst:
"""Pass through attr requests to signals to simplify connection API.
The goal is to enable `worker.yielded.connect` instead of
`worker.signals.yielded.connect`. Because multiple inheritance of Qt
classes is not well supported in PyQt, we have to use composition here
(signals are provided by QObjects, and QRunnable is not a QObject). So
this passthrough allows us to connect to signals on the `_signals`
object.
"""
# the Signal object is actually a class attribute
attr = getattr(self.signals.__class__, name, None)
if isinstance(attr, Signal):
# but what we need to connect to is the instantiated signal
# (which is of type `SignalInstance` in PySide and
# `pyqtBoundSignal` in PyQt)
return getattr(self.signals, name)
raise AttributeError(
f"{self.__class__.__name__!r} object has no attribute {name!r}"
)
[docs] def quit(self) -> None:
"""Send a request to abort the worker.
!!! note
It is entirely up to subclasses to honor this method by checking
`self.abort_requested` periodically in their `worker.work`
method, and exiting if `True`.
"""
self._abort_requested = True
@property
def abort_requested(self) -> bool:
"""Whether the worker has been requested to stop."""
return self._abort_requested
@property
def is_running(self) -> bool:
"""Whether the worker has been started."""
return self._running
[docs] def run(self) -> None:
"""Start the worker.
The end-user should never need to call this function.
But it cannot be made private or renamed, since it is called by Qt.
The order of method calls when starting a worker is:
```
calls QThreadPool.globalInstance().start(worker)
| triggered by the QThreadPool.start() method
| | called by worker.run
| | |
V V V
worker.start -> worker.run -> worker.work
```
**This** is the function that actually gets called when calling
`QThreadPool.start(worker)`. It simply wraps the `work()`
method, and emits a few signals. Subclasses should NOT override this
method (except with good reason), and instead should implement
`work()`.
"""
self.started.emit()
self._running = True
try:
with warnings.catch_warnings():
warnings.filterwarnings("always")
warnings.showwarning = lambda *w: self.warned.emit(w)
result = self.work()
if isinstance(result, Exception):
if isinstance(result, RuntimeError):
# The Worker object has likely been deleted.
# A deleted wrapped C/C++ object may result in a runtime
# error that will cause segfault if we try to do much other
# than simply notify the user.
warnings.warn(
f"RuntimeError in aborted thread: {result}",
RuntimeWarning,
)
return
else:
raise result
if not self.abort_requested:
self.returned.emit(result)
except Exception as exc:
self.errored.emit(exc)
self._running = False
self.finished.emit()
self._finished.emit(self)
[docs] def work(self) -> Exception | _R:
"""Main method to execute the worker.
The end-user should never need to call this function.
But subclasses must implement this method (See
[`GeneratorFunction.work`][superqt.utils._qthreading.GeneratorWorker.work] for
an example implementation). Minimally, it should check `self.abort_requested`
periodically and exit if True.
Examples
--------
```python
class MyWorker(WorkerBase):
def work(self):
i = 0
while True:
if self.abort_requested:
self.aborted.emit()
break
i += 1
if i > max_iters:
break
time.sleep(0.5)
```
"""
raise NotImplementedError(
f'"{self.__class__.__name__}" failed to define work() method'
)
[docs] def start(self) -> None:
"""Start this worker in a thread and add it to the global threadpool.
The order of method calls when starting a worker is:
```
calls QThreadPool.globalInstance().start(worker)
| triggered by the QThreadPool.start() method
| | called by worker.run
| | |
V V V
worker.start -> worker.run -> worker.work
```
"""
if self in self._worker_set:
raise RuntimeError("This worker is already started!")
# This will raise a RunTimeError if the worker is already deleted
repr(self)
self._worker_set.add(self)
self._finished.connect(self._set_discard)
if QThread.currentThread().loopLevel():
# if we're in a thread with an eventloop, queue the worker to start
start_ = partial(QThreadPool.globalInstance().start, self)
QTimer.singleShot(1, start_)
else:
# otherwise start it immediately
QThreadPool.globalInstance().start(self)
@classmethod
def _set_discard(cls, obj: WorkerBase) -> None:
cls._worker_set.discard(obj)
[docs] @classmethod
def await_workers(cls, msecs: int | None = None) -> None:
"""Ask all workers to quit, and wait up to `msec` for quit.
Attempts to clean up all running workers by calling `worker.quit()`
method. Any workers in the `WorkerBase._worker_set` set will have this
method.
By default, this function will block indefinitely, until worker threads
finish. If a timeout is provided, a `RuntimeError` will be raised if
the workers do not gracefully exit in the time requests, but the threads
will NOT be killed. It is (currently) left to the user to use their OS
to force-quit rogue threads.
!!! important
If the user does not put any yields in their function, and the function
is super long, it will just hang... For instance, there's no graceful
way to kill this thread in python:
```python
@thread_worker
def ZZZzzz():
time.sleep(10000000)
```
This is why it's always advisable to use a generator that periodically
yields for long-running computations in another thread.
See [this stack-overflow
post](https://stackoverflow.com/questions/323972/is-there-any-way-to-kill-a-thread)
for a good discussion on the difficulty of killing a rogue python thread:
Parameters
----------
msecs : int, optional
Waits up to msecs milliseconds for all threads to exit and removes all
threads from the thread pool. If msecs is `None` (the default), the
timeout is ignored (waits for the last thread to exit).
Raises
------
RuntimeError
If a timeout is provided and workers do not quit successfully within
the time allotted.
"""
for worker in cls._worker_set:
worker.quit()
msecs = msecs if msecs is not None else -1
if not QThreadPool.globalInstance().waitForDone(msecs):
raise RuntimeError(
f"Workers did not quit gracefully in the time allotted ({msecs} ms)"
)
class FunctionWorker(WorkerBase[_R]):
"""QRunnable with signals that wraps a simple long-running function.
!!! note
`FunctionWorker` does not provide a way to stop a very long-running
function (e.g. `time.sleep(10000)`). So whenever possible, it is better to
implement your long running function as a generator that yields periodically,
and use the [`GeneratorWorker`][superqt.utils.GeneratorWorker] instead.
Parameters
----------
func : Callable
A function to call in another thread
*args
will be passed to the function
**kwargs
will be passed to the function
Raises
------
TypeError
If `func` is a generator function and not a regular function.
"""
def __init__(self, func: Callable[_P, _R], *args, **kwargs):
if inspect.isgeneratorfunction(func):
raise TypeError(
f"Generator function {func} cannot be used with FunctionWorker, "
"use GeneratorWorker instead",
)
super().__init__()
self._func = func
self._args = args
self._kwargs = kwargs
[docs] def work(self) -> _R:
return self._func(*self._args, **self._kwargs)
[docs]class GeneratorWorkerSignals(WorkerBaseSignals):
yielded = Signal(object) # emitted with yielded values (if generator used)
paused = Signal() # emitted when a running job has successfully paused
resumed = Signal() # emitted when a paused job has successfully resumed
aborted = Signal() # emitted when a running job is successfully aborted
class GeneratorWorker(WorkerBase, Generic[_Y, _S, _R]):
"""QRunnable with signals that wraps a long-running generator.
Provides a convenient way to run a generator function in another thread,
while allowing 2-way communication between threads, using plain-python
generator syntax in the original function.
Parameters
----------
func : callable
The function being run in another thread. May be a generator function.
SignalsClass : type, optional
A QObject subclass that contains signals, by default
GeneratorWorkerSignals
*args
Will be passed to func on instantiation
**kwargs
Will be passed to func on instantiation
"""
yielded: SigInst[_Y]
paused: SigInst[None]
resumed: SigInst[None]
aborted: SigInst[None]
def __init__(
self,
func: Callable[_P, Generator[_Y, _S | None, _R]],
*args,
SignalsClass: type[WorkerBaseSignals] = GeneratorWorkerSignals,
**kwargs,
):
if not inspect.isgeneratorfunction(func):
raise TypeError(
f"Regular function {func} cannot be used with GeneratorWorker, "
"use FunctionWorker instead",
)
super().__init__(SignalsClass=SignalsClass)
self._gen = func(*args, **kwargs)
self._incoming_value: _S | None = None
self._pause_requested = False
self._resume_requested = False
self._paused = False
# polling interval: ONLY relevant if the user paused a running worker
self._pause_interval = 0.01
self.pbar = None
[docs] def work(self) -> _R | None | Exception:
"""Core event loop that calls the original function.
Enters a continual loop, yielding and returning from the original
function. Checks for various events (quit, pause, resume, etc...).
(To clarify: we are creating a rudimentary event loop here because
there IS NO Qt event loop running in the other thread to hook into)
"""
while True:
if self.abort_requested:
self.aborted.emit()
break
if self._paused:
if self._resume_requested:
self._paused = False
self._resume_requested = False
self.resumed.emit()
else:
time.sleep(self._pause_interval)
continue
elif self._pause_requested:
self._paused = True
self._pause_requested = False
self.paused.emit()
continue
try:
_input = self._next_value()
output = self._gen.send(_input)
self.yielded.emit(output)
except StopIteration as exc:
return exc.value
except RuntimeError as exc:
# The worker has probably been deleted. warning will be
# emitted in `WorkerBase.run`
return exc
return None
[docs] def send(self, value: _S):
"""Send a value into the function (if a generator was used)."""
self._incoming_value = value
def _next_value(self) -> _S | None:
out = None
if self._incoming_value is not None:
out = self._incoming_value
self._incoming_value = None
return out
@property
def is_paused(self) -> bool:
"""Whether the worker is currently paused."""
return self._paused
[docs] def toggle_pause(self) -> None:
"""Request to pause the worker if playing or resume if paused."""
if self.is_paused:
self._resume_requested = True
else:
self._pause_requested = True
[docs] def pause(self) -> None:
"""Request to pause the worker."""
if not self.is_paused:
self._pause_requested = True
[docs] def resume(self) -> None:
"""Send a request to resume the worker."""
if self.is_paused:
self._resume_requested = True
#############################################################################
# convenience functions for creating Worker instances
@overload
def create_worker(
func: Callable[_P, Generator[_Y, _S, _R]],
*args,
_start_thread: bool | None = None,
_connect: dict[str, Callable | Sequence[Callable]] | None = None,
_worker_class: type[GeneratorWorker] | type[FunctionWorker] | None = None,
_ignore_errors: bool = False,
**kwargs,
) -> GeneratorWorker[_Y, _S, _R]:
...
@overload
def create_worker(
func: Callable[_P, _R],
*args,
_start_thread: bool | None = None,
_connect: dict[str, Callable | Sequence[Callable]] | None = None,
_worker_class: type[GeneratorWorker] | type[FunctionWorker] | None = None,
_ignore_errors: bool = False,
**kwargs,
) -> FunctionWorker[_R]:
...
def create_worker(
func: Callable,
*args,
_start_thread: bool | None = None,
_connect: dict[str, Callable | Sequence[Callable]] | None = None,
_worker_class: type[GeneratorWorker] | type[FunctionWorker] | None = None,
_ignore_errors: bool = False,
**kwargs,
) -> FunctionWorker | GeneratorWorker:
"""Convenience function to start a function in another thread.
By default, uses `FunctionWorker` for functions and `GeneratorWorker` for
generators, but a custom `WorkerBase` subclass may be provided. If so, it must be a
subclass of `WorkerBase`, which defines a standard set of signals and a run method.
Parameters
----------
func : Callable
The function to call in another thread.
_start_thread : bool
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 of `GeneratorWorker` or `FunctionWorker`, optional
The [`WorkerBase`][superqt.utils.WorkerBase] to instantiate, by default
[`FunctionWorker`][superqt.utils.FunctionWorker] will be used if `func` is a
regular function, and [`GeneratorWorker`][superqt.utils.GeneratorWorker] will be
used if it is a generator.
_ignore_errors : bool
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 : WorkerBase
An instantiated worker. If `_start_thread` was `False`, the worker
will have a `.start()` method that can be used to start the thread.
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
--------
```python
def long_function(duration):
import time
time.sleep(duration)
worker = create_worker(long_function, 10)
```
"""
worker: FunctionWorker | GeneratorWorker
if not _worker_class:
if inspect.isgeneratorfunction(func):
_worker_class = GeneratorWorker
else:
_worker_class = FunctionWorker
if not inspect.isclass(_worker_class) and issubclass(_worker_class, WorkerBase):
raise TypeError(f"Worker {_worker_class} must be a subclass of WorkerBase")
worker = _worker_class(func, *args, **kwargs)
if _connect is not None:
if not isinstance(_connect, dict):
raise TypeError("The '_connect' argument must be a dict")
if _start_thread is None:
_start_thread = True
for key, val in _connect.items():
_val = val if isinstance(val, (tuple, list)) else [val]
for v in _val:
if not callable(v):
raise TypeError(
f"_connect[{key!r}] must be a function or sequence of functions"
)
getattr(worker, key).connect(v)
# if the user has not provided a default connection for the "errored"
# signal... and they have not explicitly set `ignore_errors=True`
# Then rereaise any errors from the thread.
if not _ignore_errors and not (_connect or {}).get("errored", False):
def reraise(e):
raise e
worker.errored.connect(reraise)
if _start_thread:
worker.start()
return worker
@overload
def thread_worker(
function: Callable[_P, Generator[_Y, _S, _R]],
start_thread: bool | None = None,
connect: dict[str, Callable | Sequence[Callable]] | None = None,
worker_class: type[WorkerBase] | None = None,
ignore_errors: bool = False,
) -> Callable[_P, GeneratorWorker[_Y, _S, _R]]:
...
@overload
def thread_worker(
function: Callable[_P, _R],
start_thread: bool | None = None,
connect: dict[str, Callable | Sequence[Callable]] | None = None,
worker_class: type[WorkerBase] | None = None,
ignore_errors: bool = False,
) -> Callable[_P, FunctionWorker[_R]]:
...
@overload
def thread_worker(
function: Literal[None] = None,
start_thread: bool | None = None,
connect: dict[str, Callable | Sequence[Callable]] | None = None,
worker_class: type[WorkerBase] | None = None,
ignore_errors: bool = False,
) -> Callable[[Callable], Callable[_P, FunctionWorker | GeneratorWorker]]:
...
def thread_worker(
function: Callable | None = None,
start_thread: bool | None = None,
connect: dict[str, Callable | Sequence[Callable]] | None = None,
worker_class: type[WorkerBase] | None = None,
ignore_errors: bool = False,
):
"""Decorator that runs a function in a separate thread when called.
When called, the decorated function returns a
[`WorkerBase`][superqt.utils.WorkerBase]. See
[`create_worker`][superqt.utils.create_worker] for additional keyword arguments that
can be used
when calling the function.
The returned worker will have these signals:
- **started**: emitted when the work is started
- **finished**: emitted when the work is finished
- **returned**: emitted with return value
- **errored**: emitted with error object on Exception
It will also have a `worker.start()` method that can be used to start
execution of the function in another thread. (useful if you need to connect
callbacks to signals prior to execution)
If the decorated function is a generator, the returned worker will also
provide these signals:
- **yielded**: emitted with yielded values
- **paused**: emitted when a running job has successfully paused
- **resumed**: emitted when a paused job has successfully resumed
- **aborted**: emitted when a running job is successfully aborted
And these methods:
- **quit**: ask the thread to quit
- **toggle_paused**: toggle the running state of the thread.
- **send**: send a value into the generator. (This requires that your
decorator function uses the `value = yield` syntax)
Parameters
----------
function : callable
Function to call in another thread. For communication between threads
may be a generator function.
start_thread : bool
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]]
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]
The [`WorkerBase`][superqt.utils.WorkerBase] to instantiate, by default
[`FunctionWorker`][superqt.utils.FunctionWorker] will be used if `func` is a
regular function, and [`GeneratorWorker`][superqt.utils.GeneratorWorker] will be
used if it is a generator.
ignore_errors : bool
If `False` (the default), errors raised in the other thread will be
reraised in the main thread (makes debugging significantly easier).
Returns
-------
callable
function that creates a worker, puts it in a new thread and returns
the worker instance.
Examples
--------
```python
@thread_worker
def long_function(start, end):
# do work, periodically yielding
i = start
while i <= end:
time.sleep(0.1)
yield i
# do teardown
return 'anything'
# call the function to start running in another thread.
worker = long_function()
# connect signals here if desired... or they may be added using the
# `connect` argument in the `@thread_worker` decorator... in which
# case the worker will start immediately when long_function() is called
worker.start()
```
"""
def _inner(func):
@wraps(func)
def worker_function(*args, **kwargs):
# decorator kwargs can be overridden at call time by using the
# underscore-prefixed version of the kwarg.
kwargs["_start_thread"] = kwargs.get("_start_thread", start_thread)
kwargs["_connect"] = kwargs.get("_connect", connect)
kwargs["_worker_class"] = kwargs.get("_worker_class", worker_class)
kwargs["_ignore_errors"] = kwargs.get("_ignore_errors", ignore_errors)
return create_worker(
func,
*args,
**kwargs,
)
return worker_function
return _inner if function is None else _inner(function)
############################################################################
# This is a variant on the above pattern, it uses QThread instead of Qrunnable
# see https://doc.qt.io/qt-5/threads-technologies.html#comparison-of-solutions
# (it appears from that table that QRunnable cannot emit or receive signals,
# but we circumvent that here with our WorkerBase class that also inherits from
# QObject... providing signals/slots).
#
# A benefit of the QRunnable pattern is that Qt manages the threads for you,
# in the QThreadPool.globalInstance() ... making it easier to reuse threads,
# and reduce overhead.
#
# However, a disadvantage is that you have no access to (and therefore less
# control over) the QThread itself. See for example all of the methods
# provided on the QThread object: https://doc.qt.io/qt-5/qthread.html
if TYPE_CHECKING:
class WorkerProtocol(QObject):
finished: Signal
def work(self) -> None:
...
def new_worker_qthread(
Worker: type[WorkerProtocol],
*args,
_start_thread: bool = False,
_connect: dict[str, Callable] | None = None,
**kwargs,
):
"""Convenience function to start a worker in a `QThread`.
thread, not as the actual code or object that runs in that
thread. The QThread object is created on the main thread and lives there.
Worker objects which derive from QObject are the things that actually do
the work. They can be moved to a QThread as is done here.
??? "Mostly ignorable detail"
While the signals/slots syntax of the worker looks very similar to
standard "single-threaded" signals & slots, note that inter-thread
signals and slots (automatically) use an event-based QueuedConnection, while
intra-thread signals use a DirectConnection. See [Signals and Slots Across
Threads](https://doc.qt.io/qt-5/threads-qobject.html#signals-and-slots-across-threads>)
Parameters
----------
Worker : QObject
QObject type that implements a `work()` method. The Worker should also
emit a finished signal when the work is done.
_start_thread : bool
If True, thread will be started immediately, otherwise, thread must
be manually started with thread.start().
_connect : dict
Optional dictionary of {signal: function} to connect to the new worker.
for instance: _connect = {'incremented': myfunc} will result in:
worker.incremented.connect(myfunc)
*args
will be passed to the Worker class on instantiation.
**kwargs
will be passed to the Worker class on instantiation.
Returns
-------
worker : WorkerBase
The created worker.
thread : QThread
The thread on which the worker is running.
Examples
--------
Create some QObject that has a long-running work method:
```python
class Worker(QObject):
finished = Signal()
increment = Signal(int)
def __init__(self, argument):
super().__init__()
self.argument = argument
@Slot()
def work(self):
# some long running task...
import time
for i in range(10):
time.sleep(1)
self.increment.emit(i)
self.finished.emit()
worker, thread = new_worker_qthread(
Worker,
'argument',
_start_thread=True,
_connect={'increment': print},
)
```
"""
if _connect and not isinstance(_connect, dict):
raise TypeError("_connect parameter must be a dict")
thread = QThread()
worker = Worker(*args, **kwargs)
worker.moveToThread(thread)
thread.started.connect(worker.work)
worker.finished.connect(thread.quit)
worker.finished.connect(worker.deleteLater)
thread.finished.connect(thread.deleteLater)
if _connect:
[getattr(worker, key).connect(val) for key, val in _connect.items()]
if _start_thread:
thread.start() # sometimes need to connect stuff before starting
return worker, thread