如何在pyqtgraph中正确添加日期轴

Question

代码：

        self.graph = pg.PlotWidget(self)
        self.graph.setBackground("w")
        self.graph.showGrid(x=True, y=True)
        pen = pg.mkPen(color=(90, 169, 240),  width=5)
        self.graph.setYRange(0, 1000)
        self.plot = self.graph.plot(
            [],
            [],
            pen=pen,
            symbol='o',
            symbolSize=4,
            symbolBrush="b",
        )
        
        self.widgets.append(self.graph)
        
        
    def optimize_view(self):
        self.graph.setGeometry(6, 0, self.width(), self.height() - 50)
        
    def setup_graph(self, sym):
        if sym != 'USDT':
            try:
                data = self.get_price_history(self.parent().valute, self.time_frame)
            except:
                self.plot.setData([], [])
        else:
            pass
        new_date = datetime.now() - timedelta(len(data) - 1)
        
        res = pd.date_range(min(new_date, datetime.now()),max(new_date, datetime.now())).tolist()
        res = [datetime.timestamp(i) for i in res]
        axis_res = pd.date_range(min(new_date, datetime.now()),max(new_date, datetime.now())).strftime('%d.%m.%Y').tolist()
        self.graph.setYRange(min(data), max(data))
        self.graph.setXRange(min(res), max(res))
        print(len(res), len(data))
        
        date_axis = pg.graphicsItems.DateAxisItem.DateAxisItem(orientation = 'bottom')
        self.graph.setAxisItems(axisItems = {'bottom': date_axis})
        
        self.plot.setData(res, data)
        
    def get_price_history(self, symbol, timeframe):
        exchange = ccxt.binance()
        
        data = exchange.fetch_ohlcv(f'{symbol}/USDT', timeframe)
        
        prices = [candle[3] for candle in data]
        
        return prices

我的底部轴带有日期增量值。我需要将其替换为格式为“%d.%m.%Y”的字符串日期。我应该怎么办？我不明白文本轴是如何工作的。 self.graph 底轴必须仅包含 str-dates。

get_price_history

返回浮点值列表。

Answer 1

虽然代码存在一些缺陷，但任务很明确：使用 pyqtgraph 交互式绘制通过 ccxt 在线获取的加密货币数据。

对于主要问题，传递数字时间戳，例如

1717977600

翻译为

Monday, 10 June 2024 00:00:00

并使用 DateAxisItem

 将轴注释为日期

。

绘图是交互式的，因此，

格式取决于缩放以优化视觉体验。这意味着，放大更多以查看天数，缩小缩放以查看月份。我建议初学者继续使用它，并尝试自定义作为第二步，请参阅文档。

下面，我附上了一个固定的代码片段，其中包含一个完全工作的应用程序和一个屏幕截图

# file name: bitcoin_plot.py 
# run: python bitcoin_plot.py
import sys
from datetime import datetime, timedelta
import ccxt
import pandas as pd
import pyqtgraph as pg
from PyQt5 import QtWidgets

class BTCUSDTPlotter(QtWidgets.QWidget):
    def __init__(self, parent=None):
        super().__init__(parent)
        layout = QtWidgets.QVBoxLayout(self)
        self.graph = pg.PlotWidget()
        self.graph.showGrid(x=True, y=True)
        layout.addWidget(self.graph)

    def fetch_and_plot(self):
        # fetch BTC/USDT data from Binance
        exchange = ccxt.binance({'enableRateLimit': True})
        symbol = 'BTC/USDT'
        timeframe = '1d'
        ohlcv_data = exchange.fetch_ohlcv(symbol, timeframe)
        
        # process 
        timestamps = [x[0] / 1000 for x in ohlcv_data]  # convert to seconds
        dates = [datetime.fromtimestamp(ts) for ts in timestamps] # use numeric timestamps
        close_prices = [x[4] for x in ohlcv_data]  # https://github.com/ccxt/ccxt/blob/b6ea6bd9b88525c6110ba8f658c727b0ed6bcf62/examples/py/binance-fetch-ohlcv.py#L38

        # plot
        self.graph.plot(timestamps, close_prices, pen=pg.mkPen(color=(0, 120, 200), width=2))
        date_axis = pg.graphicsItems.DateAxisItem.DateAxisItem(orientation='bottom')
        self.graph.setAxisItems({'bottom': date_axis})


def main():
    app = QtWidgets.QApplication(sys.argv)
    window = QtWidgets.QMainWindow()
    plotter = BTCUSDTPlotter()
    plotter.fetch_and_plot()
    window.setCentralWidget(plotter)
    window.show()
    sys.exit(app.exec_())
    

if __name__ == "__main__":
    main()