I've noticed when experimenting with lists that p= p+i is different then p += i For example:

test = [0, 1, 2, 3,] p = test test1 = [8] p = p + test1 print test 

In the above code test prints out to the original value of [0, 1, 2, 3,]

But if I switch p = p + test1 with p += test1 As in the following

test = [0, 1, 2, 3,] p = test test1 = [8] p += test1 print test 

test now equals [0, 1, 2, 3, 8]

What is the reason for the different value?