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I was wondering if anyone had any good solutions to the pickling error I am having at the moment. I am trying to set my code up to open several different processes in parallel, each with a fitting process to be display on a matplotlib canvas in real time. Within my main application, I have a button which activates this function:

def process_data(self):
        process_list = []
        for tab in self.tab_list:
            process_list.append(mp.Process(target=process_and_fit, args=(tab,)))
            process_list[-1].start()
            process_list[-1].join()
        return

As you may notice, a 'tab' (PyQt4.QtGui.QTabWidget object) is passed to the function process_and_fit, which I have noticed is not able to be pickled readily (link here) . However, I am not certain how to change the code to get rid of the frame being passed since it needs to be called in the process_and_fit function indirectly. By indirectly I mean something like this: (psuedo code again)

def process_and_fit(tab): # this just sets up and starts the fitting process
        result = lmfit.Minimizer(residual, parameters, fcn_args=(tab,))
        result.prepare_fit()
        result.leastsq()

def residual(params, tab):
    residual_array = Y - model
    tab.refreshFigure()
    return residual_array

class tab(QtGui.QTabWidget):
    def __init__(self, parent, spectra):
       # stuff to initialize the tab widget and hold all of the matplotlib lines and canvases

    # This just refreshes the GUI stuff everytime that the parameters are fit in the least squares method
    def refreshFigure(self):     
        self.line.set_data(self.spectra.X, self.spectra.model)
        self.plot.draw_artist(self.line)
        self.plot.figure.canvas.blit(self.plot.bbox)

Does anyone know how to get around this pickling error since the tab associated with a process should have only one set of data associated with it? I looked at Steven Bethard's approach but I really didn't understand where to put the code or how to utilize it. (I am a chemical engineer, not a computer scientist so there's a lot that I don't understand)

Any help is greatly appreciated.

EDIT: I added the links in that I forgot about, as requested.

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1 回答 1

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主要问题是您无法从主 UI 线程（所有 Qt 调用都在其中）的单独进程中进行 UI 更改。您需要使用mp.Pipeormp.Queue与主进程进行通信。

def process_data(self):
    for tab in self.tab_list:
        consumer, producer = mp.Pipe()
        process_list.append(mp.Process(target=process_and_fit, args=(producer,)))
        process_list[-1].start()
        while (true):
            message = consumer.recv()  # blocks
            if message == 'done':
                break
            # tab.spectra.X, tab.spectra.model = message
            tab.refreshFigure()
        process_list[-1].join()
    return

def process_and_fit(pipe_conn):
    ...
    pipe_conn.send('done')

def residual(params, pipe_conn):
    residual_array = Y - model
    pipe_conn.send('refresh')  # or replace 'refresh' with (X, model)
    return residual_array

还有一点需要注意：阻塞consumer.recv()可能会挂起 GUI 线程。有很多资源可以缓解这种情况，“子进程 Popen 阻塞 PyQt GUI ”这个问题会有所帮助，因为您可能应该切换到QThreads. （Qthread：PySide，PyQt）

使用 QThreads 而不是 Python 线程的优势在于，使用 QThreads，由于您已经在 Qt 的主事件循环中，您可以使用异步（非阻塞）回调来更新 UI。

于 2013-02-06T19:14:46.297 回答