python-3.x - 为什么 Matplotlib.rcParams.update 样式不更新 facecolor PyQt5？

Question

我正在使用 matplotlib 样式，当在组合框中选择样式时，我尝试动态更改样式。我使用的是 Matplotlib 2.2.3、Python 3.6.6、PyQt5、Windows 10。但是当我选择 dark_background 样式时，图形 facecolor 和轴 facecolor 不会改变。这里有一个动画: 这是代码:

使用 pyuic5 生成的文件 IHMDrawDates.py:

from PyQt5 import QtCore, QtGui, QtWidgets

class Ui_MplMainWindow(object):
    def setupUi(self, MplMainWindow):
        MplMainWindow.setObjectName("MplMainWindow")
        MplMainWindow.resize(628, 416)
        self.centralwidget = QtWidgets.QWidget(MplMainWindow)
        self.centralwidget.setObjectName("centralwidget")
        self.gridLayout_2 = QtWidgets.QGridLayout(self.centralwidget)
        self.gridLayout_2.setObjectName("gridLayout_2")
        self.mpl = MplWidgetTest(self.centralwidget)
        sizePolicy = QtWidgets.QSizePolicy(QtWidgets.QSizePolicy.Expanding, QtWidgets.QSizePolicy.Expanding)
        sizePolicy.setHorizontalStretch(0)
        sizePolicy.setVerticalStretch(0)
        sizePolicy.setHeightForWidth(self.mpl.sizePolicy().hasHeightForWidth())
        self.mpl.setSizePolicy(sizePolicy)
        self.mpl.setObjectName("mpl")
        self.gridLayout_2.addWidget(self.mpl, 0, 0, 1, 1)
        self.groupBox = QtWidgets.QGroupBox(self.centralwidget)
        self.groupBox.setMaximumSize(QtCore.QSize(95, 16777215))
        self.groupBox.setObjectName("groupBox")
        self.gridLayout = QtWidgets.QGridLayout(self.groupBox)
        self.gridLayout.setObjectName("gridLayout")
        self.buttonDrawDate = QtWidgets.QPushButton(self.groupBox)
        self.buttonDrawDate.setMaximumSize(QtCore.QSize(75, 16777215))
        self.buttonDrawDate.setObjectName("buttonDrawDate")
        self.gridLayout.addWidget(self.buttonDrawDate, 1, 0, 1, 1)
        self.buttonErase = QtWidgets.QPushButton(self.groupBox)
        self.buttonErase.setMaximumSize(QtCore.QSize(75, 16777215))
        self.buttonErase.setObjectName("buttonErase")
        self.gridLayout.addWidget(self.buttonErase, 2, 0, 1, 1)
        spacerItem = QtWidgets.QSpacerItem(20, 40, QtWidgets.QSizePolicy.Minimum, QtWidgets.QSizePolicy.Expanding)
        self.gridLayout.addItem(spacerItem, 3, 0, 1, 1)
        self.comboTema = QtWidgets.QComboBox(self.groupBox)
        self.comboTema.setObjectName("comboTema")
        self.gridLayout.addWidget(self.comboTema, 0, 0, 1, 1)
        self.gridLayout_2.addWidget(self.groupBox, 0, 1, 1, 1)
        MplMainWindow.setCentralWidget(self.centralwidget)
        self.menubar = QtWidgets.QMenuBar(MplMainWindow)
        self.menubar.setGeometry(QtCore.QRect(0, 0, 628, 21))
        self.menubar.setObjectName("menubar")
        MplMainWindow.setMenuBar(self.menubar)
        self.statusbar = QtWidgets.QStatusBar(MplMainWindow)
        self.statusbar.setObjectName("statusbar")
        MplMainWindow.setStatusBar(self.statusbar)

        self.retranslateUi(MplMainWindow)
        QtCore.QMetaObject.connectSlotsByName(MplMainWindow)

    def retranslateUi(self, MplMainWindow):
        _translate = QtCore.QCoreApplication.translate
        MplMainWindow.setWindowTitle(_translate("MplMainWindow", "MainWindow"))
        self.groupBox.setTitle(_translate("MplMainWindow", "GroupBox"))
        self.buttonDrawDate.setText(_translate("MplMainWindow", "Draw"))
        self.buttonErase.setText(_translate("MplMainWindow", "Erase"))

from mplwidgettest import MplWidgetTest

mplwidgettest.py 文件，其中包含用于更新 matplotlib 样式的“setTema”方法。当我打印变量 rcParams 时，它包含 axes.facecolor: black 但它不适用

from PyQt5.QtWidgets import QSizePolicy, QWidget, QVBoxLayout
from matplotlib.figure import Figure
from matplotlib.backends.backend_qt5agg import (
    FigureCanvasQTAgg as FigureCanvas,
    NavigationToolbar2QT as NavigationToolbar)
import matplotlib as mplib


class MplCanvas(FigureCanvas):
    """Class to represent the FigureCanvas widget"""
    def __init__(self):
        # setup Matplotlib Figure and Axis
        mplib.rcParams.update(mplib.rcParamsDefault)
        mplib.style.use('bmh')
        self.fig = Figure()
        self.ax = self.fig.add_subplot(111)
        # initialization of the canvas
        FigureCanvas.__init__(self, self.fig)
        # we define the widget as expandable
        FigureCanvas.setSizePolicy(self,
                                   QSizePolicy.Expanding,
                                   QSizePolicy.Expanding)
        # notify the system of updated policy
        FigureCanvas.updateGeometry(self)

    def setTema(self, tema='classic'):
        print(tema)
        mplib.style.use(tema)
        print(mplib.rcParams)
        mplib.rcParams.update(mplib.rcParams)


class MplWidgetTest(QWidget):
    """Widget defined in Qt Designer"""
    def __init__(self, parent=None):
        # initialization of Qt MainWindow widget
        QWidget.__init__(self, parent)
        # set the canvas to the Matplotlib widget
        self.canvas = MplCanvas()
        # create a NavigatioToolbar
        self.ntb = NavigationToolbar(self.canvas, self)
        # create a vertical box layout
        self.vbl = QVBoxLayout()
        # add mpl widget to vertical box
        self.vbl.addWidget(self.canvas)
        # add NavigationToolBar to vertical box
        self.vbl.addWidget(self.ntb)
        # set the layout to th vertical box
        self.setLayout(self.vbl)

调用前两个文件的 mainMplWidget.py 文件，包含改变 matplotlib 样式的方法 'cambiarTema'

import sys
from IHMDrawDates import Ui_MplMainWindow
from PyQt5.QtWidgets import QMainWindow, QApplication
from PyQt5.QtGui import QCursor
import numpy as np


class DesignerMainWindow(QMainWindow, Ui_MplMainWindow):

    def __init__(self, parent=None):
        super(DesignerMainWindow, self).__init__(parent)
        self.setupUi(self)
        self.posX = []
        self.posY = []
        temas = ['bmh', 'classic', 'grayscale', 'seaborn-bright',
                 'ggplot', 'dark_background']
        self.comboTema.addItems(temas)
        # connect the signals with the slots
        self.buttonDrawDate.clicked.connect(self.drawDate)
        self.buttonErase.clicked.connect(self.eraseDate)
        self.comboTema.currentIndexChanged.connect(self.cambiarTema)

    def cambiarTema(self):
        tema = self.comboTema.currentText()
        self.mpl.canvas.setTema(str(tema))
        self.mpl.canvas.ax.clear()
        self.mpl.canvas.draw()
        self.mpl.canvas.flush_events()

    def drawDate(self):
        x = np.arange(0, 100, 0.1)
        y = np.sin(x)
        self.mpl.canvas.ax.plot(x, y)
        self.mpl.canvas.ax.relim()
        self.mpl.canvas.ax.autoscale(True)
        self.mpl.ntb.update()
        self.mpl.ntb.push_current()
        self.mpl.canvas.draw()

    def eraseDate(self):
        self.mpl.canvas.ax.clear()
        self.mpl.ntb.update()
        self.mpl.ntb.push_current()
        self.mpl.canvas.draw()

if __name__ == '__main__':
    app = 0
    app = QApplication(sys.argv)
    dmw = DesignerMainWindow()
    # show it
    dmw.show()
    sys.exit(app.exec_())

Answer 1

下面解释为什么设置新的样式不会更新已有的图形。

matplotlib.rcParams本质上是一个字典，它存储了在 matplotlib 中创建对象时要使用的某些默认参数。rcParams.update 会更新这个字典； update是 python dict 对象的一个​​方法。 matplotlib.style.use是更新 rcParams 的快捷方式，它将从文件或字典中加载相应的参数。

然后在创建新对象时使用这些参数。以简化的方式，这看起来像

def create_object(arg1, parameter1=None):
    if not parameter1:
        # use the default from the rcParams
        parameter1 = rcParams["parameter1"]
    obj = MatplotlibObject(arg1, parameter1=parameter1)
    return obj

创建对象时会用到这个函数。但是，一旦创建了这样的对象，当 rcParams 中的某些内容发生更改时，它不会再次运行。

obj = create_object(1)
rcParams.update({"parameter1" : "New Value"})
# at this point, obj would not know about the new parameter1 value

如前所述，有两种选择。

• 手动更改参数。您可以在创建对象后手动更改参数。

  obj = create_object(1)
  obj.set_parameter1("New Value")
  

• 重新创建对象。您可以删除现有对象，更新 rcParams 并重新创建对象，以便它使用新值。

  obj = create_object(1)
  del obj
  rcParams.update({"parameter1" : "New Value"})
  obj = create_object(1)