In this article we will see how we can get the y-change signal for 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. Y change signal is emitted when the Y value of the bar graph is changed by default it is 0.
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 use yChanged.connect method with the bar graph object
Syntax : bargraph.yChanged.connect(method)
Argument : It takes method as argument
Return : It returns None
Below is the implementation
Python3
# importing Qt widgetsfrom PyQt5.QtWidgets import * import sys# importing pyqtgraph as pgimport pyqtgraph as pgfrom PyQt5.QtGui import *# Bar Graph classclass 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 Y value (from origin) self.setY(1000)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("Geeksforneveropen") # 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') # 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) # adding label in the layout layout.addWidget(label, 1, 0) # 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) # signal emitted when y is changed bargraph.yChanged.connect(lambda: do_action()) # do action method called by bar graph def do_action(): # setting text to the label label.setText("y value of bar graph is Changed")# create pyqt5 appApp = QApplication(sys.argv)# create the instance of our Windowwindow = Window()# start the appsys.exit(App.exec()) |
Output :
