The checkbox value printing twice when checkbox checked in in tree view

The checkbox value printing twice when checkbox checked in in tree view

I am new to pythin programming.I need to implement tree view with
checkbox. Below is the code for tree view with checkbox:
import Tix
class View(object):
def __init__(self, root):
self.root = root
self.makeCheckList()
def makeCheckList(self):
self.cl = Tix.CheckList(self.root, browsecmd=self.selectItem)
self.cl.pack()
self.cl.hlist.add("CL1", text="checklist1")
self.cl.hlist.add("CL1.Item1", text="subitem1")
self.cl.hlist.add("CL2", text="checklist2")
self.cl.hlist.add("CL2.Item1", text="subitem1")
self.cl.setstatus("CL2", "on")
self.cl.setstatus("CL2.Item1", "on")
self.cl.setstatus("CL1", "off")
self.cl.setstatus("CL1.Item1", "off")
self.cl.autosetmode()
def selectItem(self, item):
print item, self.cl.getstatus(item)
def main():
root = Tix.Tk()
view = View(root)
root.update()
root.mainloop()
if __name__ == '__main__':
main()
There is a problem if a checkbox is checked the value of checkbox gets
printed twice for single checkin.
Can anyone please help me to solve the issue such that the value has to be
printed once for single checki.