Question

In this code:
http://dpaste.com/1026946/

How can I avoid mutating L2 simultaneously with L1? How to separate them?

Answer 1

You cannot. All variables in Python are passed by reference, instead of by value.

Answer 2

http://pastebin.com/Cz1ta0Wm

L2(list) changing because it contain 2 reference links to L1(list) not values
one refernce at [0] index another one at [1] index
to avoid mutating u should assign value of L1 to L2 at index's [0] and [1]
L2 = [L1[0], L1[0]]

Answer 3

http://dpaste.com/1027733/
http://henry.precheur.org/python/copy_list
http://effbot.org/zone/python-list.htm

Answer 4

http://www.greenteapress.com/thinkpython/thinkCSpy/html/chap08.html
http://effbot.org/pyfaq/how-do-i-copy-an-object-in-python.htm

Answer 5

http://python.net/~mwh/hacks/objectthink.html

Answer 6

use this instead
l1=[2]
l2=[l1,l1]
print 'l2=',l2
l2[0]=3
print 'l2=',l2