So it looks like updating the plot data from an outside thread is just a
Bad Idea. Here is the same example wrapping the callback in a Qt
Signal/Slot pattern. Note that signals need to be defined inside a QObject,
hence the explicit instantiation of a GraphicsLayoutWidget. So far it seems
to work as expected.
import numpy as np
from PyQt5 import QtWidgets
from PyQt5.QtCore import pyqtSignal, pyqtSlot
import pyqtgraph as pg
from pyqtgraph.Qt import QtCore, QtGui
from pyqtgraph import GraphicsLayoutWidget
from threading import Thread, Event
import time
# Routine to acquire and serve data
# This might be a camera driver, notifying when a new frame is available
def generate_data(callback, threadkill):
while not threadkill.is_set():
width = 1600
data = np.zeros(width)
data += np.cos(np.arange(0, 10*np.pi, 10*np.pi/width) -
9*time.monotonic())
data += np.cos(np.arange(0, 4*np.pi, 4*np.pi/width) +
4*time.monotonic())
callback(data)
time.sleep(0.01)
class PyQtGraphTest(GraphicsLayoutWidget):
# Signal to indicate new data acquisition
# Note: signals need to be defined inside a QObject class/subclass
data_acquired = pyqtSignal(np.ndarray)
def __init__(self):
super().__init__()
self.setWindowTitle('Test pyqtgraph paint signals')
self.resize(640, 400)
self.plot = self.addPlot()
self.spectrum = self.plot.plot()
self.plot.enableAutoRange(pg.ViewBox.XYAxes)
# Connect the signal
self.data_acquired.connect(self.update_data)
# Make and start the background thread to acquire data
# Pass it the signal.emit as the callback function
self.threadkill = Event()
self.thread = Thread(target=generate_data,
args=(self.data_acquired.emit, self.threadkill))
self.thread.start()
# Kill our data acquisition thread when shutting down
def closeEvent(self, close_event):
self.threadkill.set()
# Slot to receive acquired data and update plot
@pyqtSlot(np.ndarray)
def update_data(self, data):
self.spectrum.setData(data)
if __name__ == '__main__':
import sys
app = QtWidgets.QApplication(sys.argv)
window = PyQtGraphTest()
window.show()
if (sys.flags.interactive != 1) or not hasattr(QtCore, 'PYQT_VERSION'):
sys.exit(app.exec_())
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