在 PyQt4 中使用 PyQtGraph 实时绘图 [英] Live Plotting with PyQtGraph in PyQt4

问题描述

我是 Python 新手，正在尝试制作 PyQt4 应用程序，我将 PyQtGraph 嵌入其中.我有这个 PyQtGraph 实时绘图仪，它工作得非常好:

I am quite new in Python and TRYING to make a PyQt4 app, where I am embedding PyQtGraph in it. I've got this PyQtGraph live plotter that works fantastically:

from pyqtgraph.Qt import QtGui, QtCore
import pyqtgraph as pg
import random

app = QtGui.QApplication([])
p = pg.plot()
curve = p.plot()
data = [0]

def updater():

    data.append(random.random())
    curve.setData(data) #xdata is not necessary


timer = QtCore.QTimer()
timer.timeout.connect(updater)
timer.start(0)

if __name__ == '__main__':
    import sys
    if (sys.flags.interactive != 1) or not hasattr(QtCore, 'PYQT_VERSION'):
        QtGui.QApplication.instance().exec_()

为了嵌入更大的 PyQt4 应用程序，我需要一个包含 pyqtgraph.PlotWidget() 的布局.为此，我在 MainWindow 中设置了一个 centralWidget.我创建了一个按钮，它应该像前面的代码一样开始绘图，但是当我通过绘图仪函数调用更新程序函数时什么也没有发生:

For embedding in a bigger PyQt4 app, I need a layout for including a pyqtgraph.PlotWidget(). For that matter I set a centralWidget in my MainWindow. I create a button, that should start plotting just as the previous code does, but just nothing happens when I call the updater function through the plotter function:

import sys
from PyQt4 import QtCore, QtGui
import pyqtgraph as pg
import random

class MainWindow(QtGui.QMainWindow):
    def __init__(self, parent=None):
        super(MainWindow, self).__init__(parent)
        self.central_widget = QtGui.QStackedWidget()
        self.setCentralWidget(self.central_widget)
        login_widget = LoginWidget(self)#to say where the button is
        login_widget.button.clicked.connect(self.plotter)
        self.central_widget.addWidget(login_widget)

    def plotter(self):
        self.data =[0]
        timer = QtCore.QTimer()
        timer.timeout.connect(self.updater)
        timer.start(0)

    def updater(self):

        self.data.append(random.random())
        plot.setData(self.data)

class LoginWidget(QtGui.QWidget):
    def __init__(self, parent=None):
        global plot
        super(LoginWidget, self).__init__(parent)
        layout = QtGui.QHBoxLayout()
        self.button = QtGui.QPushButton('Start Plotting')
        layout.addWidget(self.button)
        plot = pg.PlotWidget()
        layout.addWidget(plot)
        self.setLayout(layout)

if __name__ == '__main__':
    app = QtGui.QApplication([])
    window = MainWindow()
    window.show()
    app.exec_()

没有任何事情发生，因为我必须穿线吗?

Is nothing happening because I have to thread?

推荐答案

代码中有几件事情需要考虑.
首先，按照与@luddek 的回答相同的方向，您需要跟踪变量.如果你在类方法中定义了一个变量并且这个类方法执行完毕，那么这个变量就会丢失.从外面也看不到它.
因此，最好使用实例变量，
self.plot 而不是 plot
self.timer 而不是 timer
self.login_widget 而不是 login_widget
(另外，我不建议在 PyQt 程序中使用 global，尽管它是有效的代码)

There are several things to consider in the code.
First, going in the same direction as @luddek's answer, you need to keep track of your variables. If you define a variable inside a class method and this class method finished executing, the variable is lost. Also it is not visible from the outside.
It is therefore a good idea to use instance variables,
self.plot instead of plot
self.timer instead of timer
self.login_widget instead of login_widget
(also, I would not recomment using global in a PyQt programm, although it is valid code)

接下来，PlotWidget 没有 setData 方法.将数据绘制到 PlotItem 的绘图中稍微复杂一点:
pg.PlotWidget() 有一个 PlotItem，你可以通过 .getPlotItem() 获得它.然后你需要在它上面调用 plot() ，它返回你想要添加数据的实际曲线.在下面的示例中，我引入了新变量 self.curve，您可以通过 self.curve.setData(self.data)

Next, PlotWidget does not have a setData method. Plotting the data to the PlotItem's plot is a little more involved:
pg.PlotWidget() has a PlotItem which you can get via .getPlotItem(). Then you need to invoke plot() on it, which returns the actual curve you want to add data to. In the example below I introduced the new variable self.curve to which you can add the data via self.curve.setData(self.data)

这是完整的工作代码.

from PyQt4 import QtCore, QtGui
import pyqtgraph as pg
import random

class MainWindow(QtGui.QMainWindow):
    def __init__(self, parent=None):
        super(MainWindow, self).__init__(parent)
        self.central_widget = QtGui.QStackedWidget()
        self.setCentralWidget(self.central_widget)
        self.login_widget = LoginWidget(self)
        self.login_widget.button.clicked.connect(self.plotter)
        self.central_widget.addWidget(self.login_widget)

    def plotter(self):
        self.data =[0]
        self.curve = self.login_widget.plot.getPlotItem().plot()

        self.timer = QtCore.QTimer()
        self.timer.timeout.connect(self.updater)
        self.timer.start(0)

    def updater(self):

        self.data.append(self.data[-1]+0.2*(0.5-random.random()) )
        self.curve.setData(self.data)

class LoginWidget(QtGui.QWidget):
    def __init__(self, parent=None):
        super(LoginWidget, self).__init__(parent)
        layout = QtGui.QHBoxLayout()
        self.button = QtGui.QPushButton('Start Plotting')
        layout.addWidget(self.button)
        self.plot = pg.PlotWidget()
        layout.addWidget(self.plot)
        self.setLayout(layout)

if __name__ == '__main__':
    app = QtGui.QApplication([])
    window = MainWindow()
    window.show()
    app.exec_()

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