Python Unbound Method TypeError

The method get_pos is supposed to grab what the user inputs in the entry. When get_pos is executed, it returns with:

TypeError: unbound method get_pos() must be called with app instance as first argument (got nothing instead)

Code:

class app(object):
    def __init__(self,root):
        self.functionframe=FunctionFrame(root, self)
            self.functionframe.pack(side=BOTTOM)
    def get_pos(self):
        self.functionframe.input(self)
class FunctionFrame(Frame):
    def __init__(self,master,parent):
        Frame.__init__(self,master,bg="grey90")
        self.entry = Entry(self,width=15)
        self.entry.pack
    def input(self):
        self.input = self.entry.get()
        return self.input