Parameters passing in Python

[kk]

When I learnt Java, I was told that for its primitive types, parameter 
passing is done by value. For objects, by reference.
I started to learn Python months ago, but I still can't figure out the 
parameter passing style of Python. List, Dict, Object...
When I search in mailing list, I found that someone raised the same 
question and someone responded Python uses 'pass by object'.
Would anyone explain a bit more in detail?
Thank you in advance.