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PyQtGraph – Setting Shadow Pen of Line in Line Graph
  • Last Updated : 25 Sep, 2020

In this article we will see how we can set shadow pen of the line in line graph of the PyQtGraph module. PyQtGraph is a graphics and user interface library for Python that provides functionality commonly required in designing and science applications. Its primary goals are to provide fast, interactive graphics for displaying data (plots, video, etc.) A line chart or line plot or line graph or curve chart is a type of chart which displays information as a series of data points called ‘markers’ connected by straight line segments. It is a basic type of chart common in many fields. Line graph is created with the help of plot class in PyQtGraph. Shadow Pen is basically used to draw lines between points (this is for enhancing contrast or emphacizing data).

We can create a plot window and create lines on it with the help of commands given below

# creating a pyqtgraph plot window
plt = pg.plot()

# ploting line in green color
# with dot symbol as x, not a mandatory field
line = plt.plot(x, y, pen='g', symbol='x', symbolPen='g', symbolBrush=0.2, name='green')

In order to do this we use setShadowPen method with the line object

Syntax : line.setShadowPen(QColor(168, 34, 3))

Argument : It takes QColor/QBrush/QPen object as argument

Return : It returns None

Below is the implementation

# importing Qt widgets
from PyQt5.QtWidgets import * import sys
# importing pyqtgraph as pg
import pyqtgraph as pg
from PyQt5.QtGui import *
# Bar Graph class
class BarGraphItem(pg.BarGraphItem):
    # constructor which inherit original
    # BarGraphItem
    def __init__(self, *args, **kwargs):
        pg.BarGraphItem.__init__(self, *args, **kwargs)
    # creating a mouse double click event
    def mouseDoubleClickEvent(self, e):
        # setting scale
class Window(QMainWindow):
    def __init__(self):
        # setting title
        # setting geometry
        self.setGeometry(100, 100, 600, 500)
        # icon
        icon = QIcon("skin.png")
        # setting icon to the window
        # calling method
        # showing all the widgets
    # method for components
    def UiComponents(self):
        # creating a widget object
        widget = QWidget()
        # creating a new label
        label = QLabel("GeeksforGeeks Line Plot")
        # making it multiline
        # y values to plot by line 1
        y = [2, 8, 6, 8, 6, 11, 14, 13, 18, 19]
        # y values to plot by line 2
        y2 = [3, 1, 5, 8, 9, 11, 16, 17, 14, 16]
        x = range(0, 10)
        # create plot window object
        plt = pg.plot()
        # showing x and y grids
        plt.showGrid(x = True, y = True)
        # adding legend
        # set properties of the label for y axis
        plt.setLabel('left', 'Vertical Values', units ='y')
        # set properties of the label for x axis
        plt.setLabel('bottom', 'Horizontal Vlaues', units ='s')
        # setting horizontal range
        plt.setXRange(0, 10)
        # setting vertical range
        plt.setYRange(0, 20)
        # ploting line in green color
        # with dot symbol as x, not a mandatory field
        line1 = plt.plot(x, y, pen ='g', symbol ='x', symbolPen ='g', symbolBrush = 0.2, name ='green')
        # ploting line2 with blue color
        # with dot symbol as o
        line2 = plt.plot(x, y2, pen ='b', symbol ='o', symbolPen ='b', symbolBrush = 0.2, name ='blue')
        # setting shadow pen of the line 1
        line1.setShadowPen(QColor(18, 134, 3))
        # label minimum width
        # Creating a grid layout
        layout = QGridLayout()
        # setting this layout to the widget
        # adding label to the layout
        layout.addWidget(label, 1, 0)
        # plot window goes on right side, spanning 3 rows
        layout.addWidget(plt, 0, 1, 3, 1)
        # setting this widget as central widget of the main widow
# create pyqt5 app
App = QApplication(sys.argv)
# create the instance of our Window
window = Window()
# start the app

Output :

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