PyQtGraph – X Change Signal for Bar Graph - GeeksforGeeks

29 Nov, 2021
In this article we will see how we can get the x-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. X change signal is emitted when the X 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 xChanged.connect method with the bar graph objectSyntax : bargraph.xChanged.connect(method)Argument : It takes method as argumentReturn : 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 X value (from origin)        self.setX(200)   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")         # 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 x  is changed        bargraph.xChanged.connect(lambda: do_action())         # do action method called by bar graph        def do_action():             # setting text to the label            label.setText("X 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 : 
sweetyty
Python-gui
Python-PyQt
Python-PyQtGraph
Python
Writing code in comment?
Please use ide.geeksforgeeks.org,
generate link and share the link here.
Comments
Old Comments
Python Dictionary
How to Install PIP on Windows ?
Read a file line by line in Python
Enumerate() in Python
Iterate over a list in Python
Different ways to create Pandas Dataframe
Python program to convert a list to string
Create a Pandas DataFrame from Lists
Python String | replace()
Reading and Writing to text files in Python