如何使用pyqtgraph的TimeAxisItem使X轴时间动态刷新

Question

我将从一系列数据中制作实时曲线。首先，我建立了一个数量字典，其中包含3组数据。当前程序可以动态绘制曲线。X轴也可以显示时间，并且实时更新。然而，在X轴上不同点的时间始终是相同的值。

UNIX_EPOCH_naive = datetime.datetime(1970, 1, 1, 0, 0) #offset-naive datetime
UNIX_EPOCH_offset_aware = datetime.datetime(1970, 1, 1, 0, 0, tzinfo = pytz.utc) #offset-aware datetime
UNIX_EPOCH = UNIX_EPOCH_naive

TS_MULT_us = 1e6

def now_timestamp(ts_mult=TS_MULT_us, epoch=UNIX_EPOCH):
    return(int((datetime.datetime.utcnow() - epoch).total_seconds()*ts_mult))

def int2dt(ts, ts_mult=TS_MULT_us):
    tz = pytz.timezone('Asia/Shanghai')
    user_ts = int(time.time())
    d1 = datetime.datetime.fromtimestamp(float(user_ts))
    d1x = tz.localize(d1)
    return(d1x)

def dt2int(dt, ts_mult=TS_MULT_us, epoch=UNIX_EPOCH):
    delta = dt - epoch
    return(int(delta.total_seconds()*ts_mult))

def td2int(td, ts_mult=TS_MULT_us):
    return(int(td.total_seconds()*ts_mult))

def int2td(ts, ts_mult=TS_MULT_us):
    return(datetime.timedelta(seconds=float(ts)/ts_mult))

class TimeAxisItem(pg.AxisItem):
    def __init__(self, *args, **kwargs):
        super(TimeAxisItem, self).__init__(*args, **kwargs)
    def tickStrings(self, values, scale, spacing):
        return [int2dt(value).strftime("%H:%M:%S") for value in values]

p = win.addPlot(title="Data-Time Graph", axisItems={'bottom': TimeAxisItem(orientation='bottom')})
data_dict = {}
p.addLegend() 
data_x=[]


def getDate():
    ......
    .....
    curve = p.plot(pen = color[len(data_dict)],name=name)
    data_dict[name] = [curve] # dictionary: {key:[curve,[dadta1,data2,...]]}
    data_dict[name].append([val])

def addToDisplay():
    p.plot()
    for i in data_dict.items():
        data = i[1][1] #
        curve = i[1][0] #
        if(len(data) > data_frequency):#
             data_y=data[- data_frequency:]
        else:
             data_y = data[:]
        curve.setData(data_y)#

if __name__ == "__main__":
    th= threading.Thread(target=getDate)# 
    th.start()
    timer = pg.QtCore.QTimer()
    timer.timeout.connect(addToDisplay) 
    timer.start(10)

我的希望是X轴可以动态刷新，最新的时间在右侧，过去的时间在左侧。

- autogyro

---

你能帮我吗？在PyQt4中请求帮助。 - Hamza Khan

Answer 1

我不确定你想要实现什么，因为你的代码无法运行，但是看起来你正在尝试创建一个时间戳图。这是一个使用TimeAxisItem跟踪X轴经过时间的小部件。

PyQt5

from PyQt5 import QtCore, QtGui, QtWidgets
from threading import Thread
from collections import deque
import pyqtgraph as pg
import numpy as np
import random
import sys
import time

"""Scrolling Timestamp Plot Widget Example"""

class TimeAxisItem(pg.AxisItem):
    """Internal timestamp for x-axis"""
    def __init__(self, *args, **kwargs):
        super(TimeAxisItem, self).__init__(*args, **kwargs)

    def tickStrings(self, values, scale, spacing):
        """Function overloading the weak default version to provide timestamp"""

        return [QtCore.QTime().currentTime().addMSecs(value).toString('mm:ss') for value in values]

class ScrollingTimestampPlot(QtGui.QWidget):
    """Scrolling plot widget with timestamp on x-axis and dynamic y-axis"""

    def __init__(self, parent=None):
        super(ScrollingTimestampPlot, self).__init__(parent)

        # Internal timestamp for x-axis
        self.timestamp = QtCore.QTime()
        self.timestamp.start()

        # Desired Frequency (Hz) = 1 / self.FREQUENCY
        # USE FOR TIME.SLEEP (s)
        self.FREQUENCY = 0.025

        # Screen refresh rate to update plot (ms)
        # self.SCROLLING_TIMESTAMP_PLOT_REFRESH_RATE = 1 / Desired Frequency (Hz) * 1000
        # USE FOR TIMER.TIMER (ms)
        self.SCROLLING_TIMESTAMP_PLOT_REFRESH_RATE = self.FREQUENCY * 1000

        self.DATA_POINTS_TO_DISPLAY = 200

        # Automatically pops from left if length is full
        self.data = deque(maxlen=self.DATA_POINTS_TO_DISPLAY)

        # Create Plot Widget 
        self.scrolling_timestamp_plot_widget = pg.PlotWidget(axisItems={'bottom': TimeAxisItem(orientation='bottom')})

        # Enable/disable plot squeeze (Fixed axis movement)
        self.scrolling_timestamp_plot_widget.plotItem.setMouseEnabled(x=False, y=False)
        self.scrolling_timestamp_plot_widget.setTitle('Scrolling Timestamp Plot Example')
        self.scrolling_timestamp_plot_widget.setLabel('left', 'Value')
        self.scrolling_timestamp_plot_widget.setLabel('bottom', 'Time (s)')

        self.scrolling_timestamp_plot = self.scrolling_timestamp_plot_widget.plot()
        self.scrolling_timestamp_plot.setPen(246,212,255)

        self.layout = QtGui.QGridLayout()
        self.layout.addWidget(self.scrolling_timestamp_plot_widget)

        self.read_position_thread()
        self.start()

    def start(self):
        """Update plot"""

        self.position_update_timer = QtCore.QTimer()
        self.position_update_timer.timeout.connect(self.plot_updater)
        self.position_update_timer.start(self.get_scrolling_timestamp_plot_refresh_rate())

    def read_position_thread(self):
        """Read in data using a thread"""

        self.current_position_value = 0
        self.position_update_thread = Thread(target=self.read_position, args=())
        self.position_update_thread.daemon = True
        self.position_update_thread.start()

    def read_position(self):
        frequency = self.get_scrolling_timestamp_plot_frequency()
        while True:
            self.current_position_value = random.randint(1,101) 
            time.sleep(frequency)

    def plot_updater(self):
        self.data_point = float(self.current_position_value)

        self.data.append({'x': self.timestamp.elapsed(), 'y': self.data_point})
        self.scrolling_timestamp_plot.setData(x=[item['x'] for item in self.data], y=[item['y'] for item in self.data])

    def clear_scrolling_timestamp_plot(self):
        self.data.clear()

    def get_scrolling_timestamp_plot_frequency(self):
        return self.FREQUENCY

    def get_scrolling_timestamp_plot_refresh_rate(self):
        return self.SCROLLING_TIMESTAMP_PLOT_REFRESH_RATE

    def get_scrolling_timestamp_plot_layout(self):
        return self.layout

    def get_current_position_value(self):
        return self.current_position_value

    def get_scrolling_timestamp_plot_widget(self):
        return self.scrolling_timestamp_plot_widget

# Start Qt event loop unless running in interactive mode or using pyside
if __name__ == '__main__':
    # Create main application window
    app = QtWidgets.QApplication([])
    app.setStyle(QtGui.QStyleFactory.create("Cleanlooks"))
    mw = QtGui.QMainWindow()
    mw.setWindowTitle('Scrolling Plot Example')

    # Create scrolling plot
    scrolling_timestamp_plot_widget = ScrollingTimestampPlot()

    # Create and set widget layout
    # Main widget container
    cw = QtGui.QWidget()
    ml = QtGui.QGridLayout()
    cw.setLayout(ml)
    mw.setCentralWidget(cw)

    # Can use either to add plot to main layout
    #ml.addWidget(scrolling_timestamp_plot_widget.get_scrolling_timestamp_plot_widget(),0,0)
    ml.addLayout(scrolling_timestamp_plot_widget.get_scrolling_timestamp_plot_layout(),0,0)
    mw.show()

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

PyQt4

from PyQt4 import QtCore, QtGui
from threading import Thread
from collections import deque
import pyqtgraph as pg
import numpy as np
import random
import sys
import time

"""Scrolling Timestamp Plot Widget Example"""

class TimeAxisItem(pg.AxisItem):
    """Internal timestamp for x-axis"""
    def __init__(self, *args, **kwargs):
        super(TimeAxisItem, self).__init__(*args, **kwargs)

    def tickStrings(self, values, scale, spacing):
        """Function overloading the weak default version to provide timestamp"""

        return [QtCore.QTime().addMSecs(value).toString('mm:ss') for value in values]

class ScrollingTimestampPlot(QtGui.QWidget):
    """Scrolling plot widget with timestamp on x-axis and dynamic y-axis"""

    def __init__(self, parent=None):
        super(ScrollingTimestampPlot, self).__init__(parent)

        # Internal timestamp for x-axis
        self.timestamp = QtCore.QTime()
        self.timestamp.start()

        # Desired Frequency (Hz) = 1 / self.FREQUENCY
        # USE FOR TIME.SLEEP (s)
        self.FREQUENCY = 0.025

        # Screen refresh rate to update plot (ms)
        # self.SCROLLING_TIMESTAMP_PLOT_REFRESH_RATE = 1 / Desired Frequency (Hz) * 1000
        # USE FOR TIMER.TIMER (ms)
        self.SCROLLING_TIMESTAMP_PLOT_REFRESH_RATE = self.FREQUENCY * 1000

        self.DATA_POINTS_TO_DISPLAY = 200

        # Automatically pops from left if length is full
        self.data = deque(maxlen=self.DATA_POINTS_TO_DISPLAY)

        # Create Plot Widget 
        self.scrolling_timestamp_plot_widget = pg.PlotWidget(axisItems={'bottom': TimeAxisItem(orientation='bottom')})

        # Enable/disable plot squeeze (Fixed axis movement)
        self.scrolling_timestamp_plot_widget.plotItem.setMouseEnabled(x=False, y=False)
        self.scrolling_timestamp_plot_widget.setTitle('Scrolling Timestamp Plot Example')
        self.scrolling_timestamp_plot_widget.setLabel('left', 'Value')
        self.scrolling_timestamp_plot_widget.setLabel('bottom', 'Time (s)')

        self.scrolling_timestamp_plot = self.scrolling_timestamp_plot_widget.plot()
        self.scrolling_timestamp_plot.setPen(246,212,255)

        self.layout = QtGui.QGridLayout()
        self.layout.addWidget(self.scrolling_timestamp_plot_widget)

        self.read_position_thread()
        self.start()

    def start(self):
        """Update plot"""

        self.position_update_timer = QtCore.QTimer()
        self.position_update_timer.timeout.connect(self.plot_updater)
        self.position_update_timer.start(self.get_scrolling_timestamp_plot_refresh_rate())

    def read_position_thread(self):
        """Read in data using a thread"""

        self.current_position_value = 0
        self.position_update_thread = Thread(target=self.read_position, args=())
        self.position_update_thread.daemon = True
        self.position_update_thread.start()

    def read_position(self):
        frequency = self.get_scrolling_timestamp_plot_frequency()
        while True:
            self.current_position_value = random.randint(1,101) 
            time.sleep(frequency)

    def plot_updater(self):
        self.data_point = float(self.current_position_value)

        self.data.append({'x': self.timestamp.elapsed(), 'y': self.data_point})
        self.scrolling_timestamp_plot.setData(x=[item['x'] for item in self.data], y=[item['y'] for item in self.data])

    def clear_scrolling_timestamp_plot(self):
        self.data.clear()

    def get_scrolling_timestamp_plot_frequency(self):
        return self.FREQUENCY

    def get_scrolling_timestamp_plot_refresh_rate(self):
        return self.SCROLLING_TIMESTAMP_PLOT_REFRESH_RATE

    def get_scrolling_timestamp_plot_layout(self):
        return self.layout

    def get_current_position_value(self):
        return self.current_position_value

    def get_scrolling_timestamp_plot_widget(self):
        return self.scrolling_timestamp_plot_widget

# Start Qt event loop unless running in interactive mode or using pyside
if __name__ == '__main__':
    # Create main application window
    app = QtGui.QApplication([])
    app.setStyle(QtGui.QStyleFactory.create("Cleanlooks"))
    mw = QtGui.QMainWindow()
    mw.setWindowTitle('Scrolling Plot Example')

    # Create scrolling plot
    scrolling_timestamp_plot_widget = ScrollingTimestampPlot()

    # Create and set widget layout
    # Main widget container
    cw = QtGui.QWidget()
    ml = QtGui.QGridLayout()
    cw.setLayout(ml)
    mw.setCentralWidget(cw)

    # Can use either to add plot to main layout
    #ml.addWidget(scrolling_timestamp_plot_widget.get_scrolling_timestamp_plot_widget(),0,0)
    ml.addLayout(scrolling_timestamp_plot_widget.get_scrolling_timestamp_plot_layout(),0,0)
    mw.show()

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

- nathancy

---

这是一个非常好的例子，谢谢Nathancy。我运行了这段代码，它可以绘制曲线，但是X轴没有显示时间标签。 - autogyro

X轴仅是一条带刻度的线，但没有像您的gif所示的任何数字字符“mm:ss”，我已安装PyQT5，Python 3.6。谢谢，Nathancy。 - autogyro

强烈建议不要在QApplication中使用Python线程，而应该使用QThread。但是在这种情况下，为了简单起见，您可能只需使用QTimer来调用读取功能。 - Dennis Jensen

当我运行PyQt5版本时，它可以正常滚动，但时间戳轴标签会不断变化。这里是一个示例。我正在使用Python 3.6，macOS 11.3.2。 - Damian

对于PyQt5版本，我认为“QtCore.QTime().currentTime()”应该是“QtCore.QTime(0, 0)” - Darko