Python: AttributeError: 'bool' object has no attribute 'get'

I got this problem that both of my checkboxes when clicked the program runs correctly passing through the isRunnable method and printing the value shown on below code. But when I set both values with:

self.cbDEAvar = True

this attribute error appears. Sometimes the get() method works, sometimes it does not...

Here is the main part

Declaration

self.cbDEAvar = BooleanVar(value=False)
self.cbREAvar = BooleanVar(value=False)

When i get the error (not by clicking the check boxes, but by setting its value):

def isRunnable(self):
    aux = (self.cbDEAvar.get()) + (self.cbREAvar.get())
    print aux