How can I get tab number of active tab in wxnotebo

I want to get the active tab index for the following code whenever tab is switched. Is there any built in function?

import wx

Creating notebooks:

class PageOne(wx.Panel):
def __init__(self, parent):
    wx.Panel.__init__(self, parent)
    t = wx.StaticText(self, -1, "Histogram Plot", (20,20))
    self.currentTab=1


class PageTwo(wx.Panel):
def __init__(self, parent):
    wx.Panel.__init__(self, parent)
    t = wx.StaticText(self, -1, "This is a PageTwo object", (40,40))
    self.currentTab=2


class PageThree(wx.Panel):
    def __init__(self, parent):
        wx.Panel.__init__(self, parent)
        t = wx.StaticText(self, -1, "This is a PageThree object", (60,60))
        self.currentTab=3


class MainFrame(wx.Frame):
    def __init__(self):
    wx.Frame.__init__(self, None, title="Plots")

    # Here we create a panel and a notebook on the panel
    p = wx.Panel(self)
    nb = wx.Notebook(p)

    # create the page windows as children of the notebook
    page1 = PageOne(nb)
    page2 = PageTwo(nb)
    page3 = PageThree(nb)

    # add the pages to the notebook with the label to show on the tab
    nb.AddPage(page1, "Plot 1")
    nb.AddPage(page2, "Plot 2")
    nb.AddPage(page3, "Plot 3")

    # finally, put the notebook in a sizer for the panel to manage
    # the layout
    sizer = wx.BoxSizer()
    sizer.Add(nb, 1, wx.EXPAND)
    p.SetSizer(sizer)

# bind event to notebook
    nb.Bind(wx.EVT_NOTEBOOK_PAGE_CHANGED, self.ChangingTest)

def ChangingTest(self, evt):
    print "It worked!"

Tried GetSelection() and printing currentTab but did not find any luck there. Thanks.

Looking at the wxPython demo, it appears that you want event.GetSelection() or possibly self.GetSelection where "self" refers to the Notebook. The event that the demo example is bound to is EVT_NOTEBOOK_PAGE_CHANGED.