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PyQtGraph – Creating Graph Item

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  • Last Updated : 31 Mar, 2022
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In this article we will see how we can create a 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.
 

We can create a graphic layout widget with the help of command given below 

# creating graphics layout widget
win = pg.GraphicsLayoutWidget()

In order to plot the video we have to do the following 

  • Import the pyqtgraph, pyqt5 and numpy module.
  • Create a main window class.
  • Create a graphic layout widget and add image view box to it.
  • Create a graph item and add it to the view box.
  • Set the positions of nodes and edges i.e connections and set symbols to them.
  • Create a grid layout and add the graphic layout window to it with other widgets and set the grid widget as central widget of main window.

Below is the implementation.

Python3




# importing Qt widgets
from PyQt5.QtWidgets import *
 
# importing system
import sys
 
# importing numpy as np
import numpy as np
 
# importing pyqtgraph as pg
import pyqtgraph as pg
from PyQt5.QtGui import *
from PyQt5.QtCore import *
import pyqtgraph.ptime as ptime
 
 
# Image View class
class 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', '+']
 
        # Define the line style for each connection (this is optional)
        lines = np.array([
            (255, 0, 0, 255, 1),
            (255, 0, 255, 255, 2),
            (255, 0, 255, 255, 3),
            (255, 255, 0, 255, 2),
            (255, 0, 0, 255, 1),
            (255, 255, 255, 255, 4),
        ], dtype=[('red', np.ubyte), ('green', np.ubyte), ('blue', np.ubyte), ('alpha', np.ubyte), ('width', float)])
 
        # Update the graph
        graph_item.setData(pos=pos, adj=adj, pen=lines,
                           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)
 
 
# create pyqt5 app
App = QApplication(sys.argv)
 
# create the instance of our Window
window = Window()
 
# start the app
sys.exit(App.exec())

Output : 
 

 


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