Paranormal activity in Python: Why don't these two codes give the same result?

Question

I'm getting totally mad.

Code 1:

an = []
anadir3 = [1,2,1,2,1,2]
for i in range(3):
an += [anadir3]
for i in range(3):
an[i][2*i+1]+=1
print(an)

-------------------------------
Code 2:

an = []
an = [[1,2,1,2,1,2],[1,2,1,2,1,2],[1,2,1,2,1,2]]
for i in range(3):
an[i][2*i+1]+=1
print(an)

Answer 1

When you add anadir3 to an in your first code, you not only assign the contents of anadir3 to an. You assign anadir itself to an. Hence, by altering an, you directly alter anadir3.

In this case, an contains three copies of anadir3, and altering any copy of the three will directly alter the other remaining copies.

Answer 2

A simpler answer:

https://stackoverflow.com/questions/8744113/JUMP_LINK__&&__python__&&__JUMP_LINK-list-by-value-not-by-reference

Answer 3

Yep, python

Answer 4

How can I assign just the content, preserving its value?

Answer 5

question is this python?

Answer 6

sorry then i cant help you