PyQtGraph – Setting Pen of Graph Item

08 Dec, 2021
In this article we will see how we can set the pen of the graph item in PyQTGraph. 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 Graph is a non-linear data structure consisting of nodes and edges. The nodes are sometimes also referred to as vertices and the edges are lines or arcs that connect any two nodes in the graph. Graph consists of a finite set of vertices(or nodes) and set of Edges which connect a pair of nodes. Pen is used to draw the line of graph i.e joining edges, by setting pen we can set the color, size and opacity of each line.
We can create a graphic layout widget and graphic item with the help of command given below 
# creating graphics layout widget
win = pg.GraphicsLayoutWidget()

# creating a graph item
graph_item = pg.GraphItem()
In order to do this we use setPenmethod with the graph item objectSyntax : imv.setPen(lines)Argument : It takes numpy array as argumentReturn : It returns None 
Below is the implementation 
Python3
# importing Qt widgetsfrom PyQt5.QtWidgets import * # importing systemimport sys # importing numpy as npimport numpy as np # importing pyqtgraph as pgimport pyqtgraph as pgfrom PyQt5.QtGui import *from PyQt5.QtCore import *import pyqtgraph.ptime as ptime  # Image View classclass ImageView(pg.ImageView):     # constructor which inherit original    # ImageView    def __init__(self, *args, **kwargs):        pg.ImageView.__init__(self, *args, **kwargs) class Window(QMainWindow):     def __init__(self):        super().__init__()         # setting title        self.setWindowTitle("PyQtGraph")         # setting geometry        self.setGeometry(100, 100, 600, 500)          # icon        icon = QIcon("skin.png")         # setting icon to the window        self.setWindowIcon(icon)         # calling method        self.UiComponents()         # showing all the widgets        self.show()     # method for components    def UiComponents(self):         # creating a widget object        widget = QWidget()         # creating a label        label = QLabel("Geeksforgeeks Graph Item")         # setting minimum width        label.setMinimumWidth(130)         # making label do word wrap        label.setWordWrap(True)         # setting configuration options        pg.setConfigOptions(antialias=True)         # creating graphics layout widget        win = pg.GraphicsLayoutWidget()         # adding view box to the graphic layout widget        view = win.addViewBox()         # lock the aspect ratio        view.setAspectLocked()         # creating a graph item        graph_item = pg.GraphItem()         # adding graph item to the view box        view.addItem(graph_item)         # Define positions of nodes        pos = np.array([            [0, 0],            [10, 0],            [0, 10],            [10, 10],            [5, 5],            [15, 5]        ])         # Define the set of connections in the graph        adj = np.array([            [0, 1],            [1, 3],            [3, 2],            [2, 0],            [1, 5],            [3, 5],        ])         # Define the symbol to use for each node (this is optional)        symbols = ['o', 'x', 'o', 'o', 't', '+']         # setting data to the graph item        graph_item.setData(pos=pos, adj=adj, size=1, symbol=symbols, pxMode=False)         # Creating a grid layout        layout = QGridLayout()         # minimum width value of the label        label.setMinimumWidth(130)         # setting this layout to the widget        widget.setLayout(layout)         # adding label in the layout        layout.addWidget(label, 1, 0)         # plot window goes on right side, spanning 3 rows        layout.addWidget(win, 0, 1, 3, 1)         # setting this widget as central widget of the main window        self.setCentralWidget(widget)          # Define the line style for each connection (this is optional)        lines_pen = np.array([            (255, 0, 150, 255, 10),            (255, 0, 255, 255, 2),            (255, 0, 255, 255, 3),            (255, 255, 0, 255, 2),            (255, 0, 50, 255, 1),            (255, 255, 255, 255, 4),        ], dtype=[('red', np.ubyte), ('green', np.ubyte), ('blue', np.ubyte), ('alpha', np.ubyte), ('width', float)])         # setting pen to the graph item        graph_item.setPen(lines_pen) # create pyqt5 appApp = QApplication(sys.argv) # create the instance of our Windowwindow = Window() # start the appsys.exit(App.exec())
Output : 
 
sagartomar9927
surinderdawra388
Python-gui
Python-PyQtGraph
Python
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