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 object
Syntax : imv.setPen(lines)
Argument : It takes numpy array as argument
Return : It returns None
Below is the implementation
# 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' , '+' ]
# 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 app App = QApplication(sys.argv)
# create the instance of our Window window = Window()
# start the app sys.exit(App. exec ())
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Output :