inspect.stack() and frame

Thu Mar 11 18:05:00 EST 2010

Given this code :
# Experience with frame
import sys
import inspect
def foo():
 stack = inspect.stack()
 print "foo frame : " + str(hex(id(sys._getframe())))
def foo2():
 inspect.stack()
 print "foo2 frame : " + str(hex(id(sys._getframe())))
def bar():
 print "bar frame : " + str(hex(id(sys._getframe())))
foo()
foo()
foo2()
foo2()
bar()
bar()
Output example :
foo frame : 0x84d2c0
foo frame : 0x844bf0
foo2 frame : 0x898c90
foo2 frame : 0x898c90
bar frame : 0x898f70
bar frame : 0x898f70
Why are the ids (address) of the frame for each foo call not the same?
Or why the call to "stack = inspect.stack()" change the address of the
frame?