在 Python 上使用 PyQtChart 或 pyqtgraph 和 PyQt5 绘制流数据图表的最佳方式？

Question

我正在流式传输我想要高效绘制图表的时间序列（20 多个图表在小型计算机上实时显示）。我在 PyQt5 上尝试过 PyQtChart 和 pyqtgraph，但是对于这两个库，我最终要为我收到的每个数据重新绘制整个图表，这感觉不是最佳的。我选择了 PyQtChart，因为它可以更好地处理 DatetimeSeries，但很高兴被证明是错误的（并分享 pyqtgraph 代码，只是不想让 post 太大）。

Bellow 是我使用 PyQtChart 使用随机数据的工作代码，因此您可以运行它：

import sys
from random import randint
from typing import Union

from PyQt5.QtChart import (QChart, QChartView, QLineSeries, QDateTimeAxis, QValueAxis)
from PyQt5.QtCore import Qt, QDateTime, QTimer
from PyQt5.QtWidgets import QApplication
from PyQt5.QtWidgets import (QWidget, QGridLayout)


class Window(QWidget):
    def __init__(self, window_name: str = 'Ticker'):
        QWidget.__init__(self)
        # GUI
        self.setGeometry(200, 200, 600, 400)
        self.window_name: str = window_name
        self.setWindowTitle(self.window_name)
        layout = QGridLayout(self)

        # change the color of the window
        self.setStyleSheet('background-color:black')

        # Series
        self.high_dataset = QLineSeries()
        self.low_dataset = QLineSeries()
        self.mid_dataset = QLineSeries()

        self.low_of_day: Union[float, None] = 5
        self.high_of_day: Union[float, None] = 15

        # Y Axis
        self.time_axis_y = QValueAxis()
        self.time_axis_y.setLabelFormat("%.2f")
        self.time_axis_y.setTitleText("Price")
        # X Axis
        self.time_axis_x = QDateTimeAxis()
        self.time_axis_x.setFormat("hh:mm:ss")
        self.time_axis_x.setTitleText("Datetime")

        # Events
        self.qt_timer = QTimer()
        # QChart
        self.chart = QChart()
        self.chart.addSeries(self.mid_dataset)
        self.chart.addSeries(self.high_dataset)
        self.chart.addSeries(self.low_dataset)

        self.chart.setTitle("Barchart Percent Example")
        self.chart.setTheme(QChart.ChartThemeDark)

        # https://linuxtut.com/fr/35fb93c7ca35f9665d9f/

        self.chart.legend().setVisible(True)
        self.chart.legend().setAlignment(Qt.AlignBottom)

        self.chartview = QChartView(self.chart)

        # using -1 to span through all rows available in the window
        layout.addWidget(self.chartview, 2, 0, -1, 3)

        self.chartview.setChart(self.chart)

    def set_yaxis(self):
        # Y Axis Settings
        self.time_axis_y.setRange(int(self.low_of_day * .9), int(self.high_of_day * 1.1))

        self.chart.addAxis(self.time_axis_y, Qt.AlignLeft)

        self.mid_dataset.attachAxis(self.time_axis_y)
        self.high_dataset.attachAxis(self.time_axis_y)
        self.low_dataset.attachAxis(self.time_axis_y)

    def set_xaxis(self):
        # X Axis Settings
        self.chart.removeAxis(self.time_axis_x)

        self.time_axis_x = QDateTimeAxis()
        self.time_axis_x.setFormat("hh:mm:ss")
        self.time_axis_x.setTitleText("Datetime")
        self.chart.addAxis(self.time_axis_x, Qt.AlignBottom)

        self.mid_dataset.attachAxis(self.time_axis_x)
        self.high_dataset.attachAxis(self.time_axis_x)
        self.low_dataset.attachAxis(self.time_axis_x)

    def start_app(self):
        self.qt_timer.timeout.connect(self.retrieveStream, )
        time_to_wait: int = 500  # milliseconds
        self.qt_timer.start(time_to_wait)

    def retrieveStream(self):
        date_px = QDateTime()
        date_px = date_px.currentDateTime().toMSecsSinceEpoch()
        print(date_px)

        mid_px = randint(int((self.low_of_day + 2) * 100), int((self.high_of_day - 2) * 100)) / 100

        self.mid_dataset.append(date_px, mid_px)
        self.low_dataset.append(date_px, self.low_of_day)
        self.high_dataset.append(date_px, self.high_of_day)

        print(f"epoch: {date_px}, mid: {mid_px:.2f}")

        self.update()

    def update(self):
        print("updating chart")

        self.chart.removeSeries(self.mid_dataset)
        self.chart.removeSeries(self.low_dataset)
        self.chart.removeSeries(self.high_dataset)

        self.chart.addSeries(self.mid_dataset)
        self.chart.addSeries(self.high_dataset)
        self.chart.addSeries(self.low_dataset)

        self.set_yaxis()
        self.set_xaxis()


if __name__ == '__main__':
    app = QApplication(sys.argv)
    window = Window()
    window.show()
    window.start_app()

    sys.exit(app.exec_())

此代码最大的问题是：

'update' 方法，基本上重新绘制图表的每个元素=>我更喜欢双端队列，refresh/update/refire 类型的解决方案
QLineSeries 似乎没有像 deque 集合那样的 maxLen，所以我最终可能会加载大量数据（理想情况下希望运行超过三个 QLineSeries）

除此之外，如果收到有关如何优化此代码的任何见解，我将不胜感激。我是 Qt/Asyncio/Threading 的新手，非常想学习。

最佳

EDIT 图表现在无需重绘即可更新 让我知道是否有更好的方法或需要改进的代码，因为我是 Qt 的新手。

感谢下面的回答 (@domarm) 我更正了我更新图表的方式，下面的 link 让我意识到我需要在每次刷新时为轴设置一个最小最大值，以便数据在范围内。


import sys
from datetime import datetime
from random import randint
from typing import Union, Optional

from PyQt5.QtChart import (QChart, QChartView, QLineSeries, QDateTimeAxis, QValueAxis)
from PyQt5.QtCore import (Qt, QDateTime, QTimer, QPointF)
from PyQt5.QtGui import QFont
from PyQt5.QtWidgets import (QWidget, QGridLayout, QLabel, QApplication)


# https://doc.qt.io/qt-5/qtcharts-modeldata-example.html

class Window(QWidget):
    running = False

    def __init__(self, window_name: str = 'Chart',
                 chart_title: Optional[str] = None,
                 geometry_ratio: int = 2,
                 histo_tick_size: int = 200):
        QWidget.__init__(self)
        # GUI
        self.window_wideness: int = 300
        self.histo_tick_size: int = histo_tick_size
        self.setGeometry(200,
                         200,
                         int(self.window_wideness * geometry_ratio),
                         self.window_wideness
                         )
        self.window_name: str = window_name
        self.setWindowTitle(self.window_name)
        self.label_color: str = 'grey'
        self.text_color: str = 'white'
        # Layout
        layout = QGridLayout(self)

        # Gui components
        bold_font = QFont()
        bold_font.setBold(True)

        self.label_last_px = QLabel('-', self)
        self.label_last_px.setFont(bold_font)
        self.label_last_px.setStyleSheet("QLabel { color : blue; }")
        layout.addWidget(self.label_last_px)

        # change the color of the window
        self.setStyleSheet('background-color:black')
        # QChart
        self.chart = QChart()
        if chart_title:
            self.chart.setTitle(chart_title)
        # Series
        self.high_dataset = QLineSeries(self.chart)
        self.high_dataset.setName("High")

        self.low_dataset = QLineSeries(self.chart)
        self.low_dataset.setName("Low")

        self.mid_dataset = QLineSeries(self.chart)
        self.mid_dataset.setName("Mid")

        self.low_of_day: Union[float, None] = 5
        self.high_of_day: Union[float, None] = 15
        self.last_data_point: dict = {"last_date": None, "mid_px": None, "low_px": None, "high_px": None}

        # Y Axis
        self.time_axis_y = QValueAxis()
        self.time_axis_y.setLabelFormat("%.2f")
        self.time_axis_y.setTitleText("Price")

        # X Axis
        self.time_axis_x = QDateTimeAxis()
        self.time_axis_x.setTitleText("Datetime")

        # Events
        self.qt_timer = QTimer()

        self.chart.setTheme(QChart.ChartThemeDark)
        self.chart.addSeries(self.mid_dataset)
        self.chart.addSeries(self.low_dataset)
        self.chart.addSeries(self.high_dataset)
        # https://linuxtut.com/fr/35fb93c7ca35f9665d9f/

        self.chart.legend().setVisible(True)
        # self.chart.legend().setAlignment(Qt.AlignBottom)

        self.chartview = QChartView(self.chart)
        # self.chartview.chart().setAxisX(self.axisX, self.mid_dataset)

        # using -1 to span through all rows available in the window
        layout.addWidget(self.chartview, 2, 0, -1, 3)

        self.chartview.setChart(self.chart)

    def set_yaxis(self):
        # Y Axis Settings
        self.time_axis_y.setRange(int(self.low_of_day * .9), int(self.high_of_day * 1.1))

        self.chart.addAxis(self.time_axis_y, Qt.AlignLeft)

        self.mid_dataset.attachAxis(self.time_axis_y)
        self.high_dataset.attachAxis(self.time_axis_y)
        self.low_dataset.attachAxis(self.time_axis_y)

    def set_xaxis(self):
        # X Axis Settings
        self.chart.removeAxis(self.time_axis_x)
        # X Axis
        self.time_axis_x = QDateTimeAxis()
        self.time_axis_x.setFormat("hh:mm:ss")
        self.time_axis_x.setTitleText("Datetime")

        point_first: QPointF = self.mid_dataset.at(0)
        point_last: QPointF = self.mid_dataset.at(len(self.mid_dataset) - 1)

        # needs to be updated each time for chart to render
        # 
        self.time_axis_x.setMin(QDateTime().fromMSecsSinceEpoch(point_first.x()).addSecs(0))
        self.time_axis_x.setMax(QDateTime().fromMSecsSinceEpoch(point_last.x()).addSecs(0))

        self.chart.addAxis(self.time_axis_x, Qt.AlignBottom)

        self.mid_dataset.attachAxis(self.time_axis_x)
        self.high_dataset.attachAxis(self.time_axis_x)
        self.low_dataset.attachAxis(self.time_axis_x)

    def _update_label_last_px(self):
        last_point: QPointF = self.mid_dataset.at(self.mid_dataset.count() - 1)
        last_date: datetime = datetime.fromtimestamp(last_point.x() / 1000)
        last_price = last_point.y()
        self.label_last_px.setText(f"Date time: {last_date.strftime('%d-%m-%y %H:%M %S')}  "
                                   f"Price: {last_price:.2f}")

    def start_app(self):
        """Start Thread generator"""
        # This method is supposed to stream data but not the issue, problem is that chart is not updating
        self.qt_timer.timeout.connect(self.update, )
        time_to_wait: int = 250  # milliseconds
        self.qt_timer.start(time_to_wait)

    def update(self):
        """ Update chart and Label with the latest data in Series"""
        print("updating chart")
        self._update_label_last_px()
        # date_px = QDateTime()
        # self.last_data_point['last_date'] = date_px.currentDateTime().toMSecsSinceEpoch()

        date_px = datetime.now().timestamp() * 1000
        self.last_data_point['last_date'] = date_px
        # Make up a price
        self.last_data_point['mid_px'] = randint(int((self.low_of_day + 2) * 100),
                                                 int((self.high_of_day - 2) * 100)) / 100
        self.last_data_point['low_date'] = self.low_of_day
        self.last_data_point['high_date'] = self.high_of_day
        print(self.last_data_point)

        # Feed datasets and simulate deque
        # https://www.qtcentre.org/threads/67774-Dynamically-updating-QChart
        if self.mid_dataset.count() > self.histo_tick_size:
            self.mid_dataset.remove(0)
            self.low_dataset.remove(0)
            self.high_dataset.remove(0)

        self.mid_dataset.append(self.last_data_point['last_date'], self.last_data_point['mid_px'])
        self.low_dataset.append(self.last_data_point['last_date'], self.last_data_point['low_date'])
        self.high_dataset.append(self.last_data_point['last_date'], self.last_data_point['high_date'])
        self.set_xaxis()
        self.set_yaxis()


if __name__ == '__main__':
    app = QApplication(sys.argv)
    window = Window()
    window.show()
    window.start_app()

    sys.exit(app.exec())

Answer 1

您可以使用 pglive 包来绘制来自实时流的数据。它基于 pyqtgraph，可以轻松处理 ~100Hz 的数据速率。
它使用 DataConnector，将数据存储在 deque 中，并使用 pyqt 信号更新绘图 thread-safe。如果您的输入数据以高速率更新，您还可以设置以赫兹为单位的更新速率。

还有一些额外的功能可用，例如引导线或十字准线，这使得在鼠标光标下显示精确值变得容易。

这是一个示例代码，基于您的输入：

import sys
import time
from random import randint
from threading import Thread
from time import sleep
from typing import Union

from PyQt5.QtWidgets import QWidget, QApplication, QGridLayout
from pglive.kwargs import Axis
from pglive.sources.data_connector import DataConnector
from pglive.sources.live_axis import LiveAxis
from pglive.sources.live_plot import LiveLinePlot
from pglive.sources.live_plot_widget import LivePlotWidget


class Window(QWidget):
    running = False

    def __init__(self, parent=None):
        super().__init__(parent)
        layout = QGridLayout(self)
        self.low_of_day: Union[float, None] = 5
        self.high_of_day: Union[float, None] = 15

        # Create one curve pre dataset
        high_plot = LiveLinePlot(pen="blue")
        low_plot = LiveLinePlot(pen="orange")
        mid_plot = LiveLinePlot(pen="green")

        # Data connectors for each plot with dequeue of 600 points
        self.high_connector = DataConnector(high_plot, max_points=600)
        self.low_connector = DataConnector(low_plot, max_points=600)
        self.mid_connector = DataConnector(mid_plot, max_points=600)

        # Setup bottom axis with TIME tick format
        # You can use Axis.DATETIME to show date as well
        bottom_axis = LiveAxis("bottom", **{Axis.TICK_FORMAT: Axis.TIME})

        # Create plot itself
        self.chart_view = LivePlotWidget(title="Line Plot - Time series @ 2Hz", axisItems={'bottom': bottom_axis})
        # Show grid
        self.chart_view.showGrid(x=True, y=True, alpha=0.3)
        # Set labels
        self.chart_view.setLabel('bottom', 'Datetime', units="s")
        self.chart_view.setLabel('left', 'Price')
        # Add all three curves
        self.chart_view.addItem(mid_plot)
        self.chart_view.addItem(low_plot)
        self.chart_view.addItem(high_plot)

        # using -1 to span through all rows available in the window
        layout.addWidget(self.chart_view, 2, 0, -1, 3)

    def update(self):
        """Generate data at 2Hz"""
        while self.running:
            timestamp = time.time()

            mid_px = randint(int((self.low_of_day + 2) * 100), int((self.high_of_day - 2) * 100)) / 100

            self.mid_connector.cb_append_data_point(mid_px, timestamp)
            self.low_connector.cb_append_data_point(self.low_of_day, timestamp)
            self.high_connector.cb_append_data_point(self.high_of_day, timestamp)

            print(f"epoch: {timestamp}, mid: {mid_px:.2f}")
            sleep(0.5)

    def start_app(self):
        """Start Thread generator"""
        self.running = True
        Thread(target=self.update).start()


if __name__ == '__main__':
    app = QApplication(sys.argv)
    window = Window()
    window.show()
    window.start_app()
    app.exec()
    window.running = False

这是它在运动中的样子：

pyqtgraph 的小缺点是对绘图外观的自定义有点笨拙。但这是因为 pqytgraph 是为速度而构建的。 pglive 还解决了您缺少时间和日期时间格式的问题。

肯定有其他好的软件包处理这个问题，但如果您的目标是获得良好的性能，这可能是一个不错的选择。

在 Python 上使用 PyQtChart 或 pyqtgraph 和 PyQt5 绘制流数据图表的最佳方式？

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