scared about refrences...

[SpreadTooThin]

I'm really worried that python may is doing some things I wasn't
expecting... but lets see...

if I pass a list to a function def fn(myList):

and in that function I modify an element in the list, then does the
callers list get modied as well.

def fn(list):
   list[1] = 0

myList = [1, 2, 3]
print myList
fn(myList)
print myList

>>> [1,2,3]
>>> [1,0,3]

How can I avoid this?  In this case this is a really simplified example
but the effects are the same...
How do I specify or create deep copies of objects that may contain
other objects that may contain other
object that may contain other objects....