How can I pass arguments to Tkinter button's callback command?

I got 2 buttons, respectively named 'ButtonA', 'ButtonB'. I want the program to print 'hello, ButtonA' and 'hello, ButtonB' if any button is clicked. My code is as follows:

def sayHi(name):
    print 'hello,', name

root = Tk()
btna = Button(root, text = 'ButtonA', command = lambda: text)
btna.pack()

When I click ButtonA, error occurs, text not defined.

I understand this error, but how can I pass ButtonA's text to lambda?