I am not sure why this behavior is this way.
at beginning of script, i want to create a bunch of empty lists and
use each one for its own purpose.
however, updating one list seems to update the others.
>>> a = b = c = []
>>> a.append('1')
>>> a.append('1')
>>> a.append('1')
>>> c
['1', '1', '1']
>>> a
['1', '1', '1']
>>> b
['1', '1', '1']