In this article we will see how we can create a parent change event with the bar graph in 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.) and second is to provide tools to aid in rapid application development (for example, property trees such as used in Qt Designer).A bar chart or bar graph is a chart or graph that presents categorical data with rectangular bars with heights or lengths proportional to the values that they represent. The bars can be plotted vertically or horizontally. A vertical bar chart is sometimes called a column chart. This event get triggered when the parent of the bar graph is changed. Every time when bar graph is putted inside some other widget or frame it parent get changed, Main window is the top parent of the bar graph.
We can create a plot window and bar graph with the help of commands given below
# creating a pyqtgraph plot window window = pg.plot() # creating a bar graph of green color bargraph = pg.BarGraphItem(x=x, height=y1, width=0.6, brush='g')
In order to do this we have modify the bar graph class, below is the class which can be used
# Bar Graph class class BarGraphItem(pg.BarGraphItem): # constructor which inherit original # BarGraphItem def __init__(self, *args, **kwargs): pg.BarGraphItem.__init__(self, *args, **kwargs) # creating parent changed event def parentChanged(self): # print the message print("Parent Changed")
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 parent changed event
def parentChanged( self ):
# print the message
print ( "Parent Changed" )
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 plot window
plot = pg.plot()
# create list for y-axis
y1 = [ 5 , 5 , 7 , 10 , 3 , 8 , 9 , 1 , 6 , 2 ]
# create horizontal list i.e x-axis
x = [ 1 , 2 , 3 , 4 , 5 , 6 , 7 , 8 , 9 , 10 ]
# create pyqt5graph bar graph item
# with width = 0.6
# with bar colors = green
bargraph = BarGraphItem(x = x, height = y1, width = 0.6 , brush = 'g' )
# bargraph.viewRangeChanged.connect(lambda: print("sss"))
# add item to plot window
# adding bargraph item to the plot window
plot.addItem(bargraph)
# Creating a grid layout
layout = QGridLayout()
# setting this layout to the widget
widget.setLayout(layout)
# plot window goes on right side, spanning 3 rows
layout.addWidget(plot, 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 ())
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Output :
Parent Changed Parent Changed