Swapping elements in a list in Python

I am trying to swap the elements of list A i.e. (i,j) turns to (j,-i). But there is an error.

A=[(0,0),(0,1),(1,0),(1,1)]

for i in range(0,len(A)-1):
    for j in range(0,len(A)-1):
        A[i][j]=A[j][-i]

The error is

in <module>
    A[i][j]=A[j][-i]

TypeError: 'tuple' object does not support item assignment

The expected output is

[(0,0),(1,0),(0,-1),(-1,-1)]

>Solution :

What you have is a list of tuples, and tuples are immutable. What you’re doing would not be described so much as "swapping elements in a list" as swapping the elements of a tuple (and negating the second one).

If you have

a = (1, 1)

then you could perform this operation like:

b = (a[1], -a[0])

Performing that over a list of items a separate level of abstraction that can be handled in many different ways. For example using a list comprehension:

A = [(0, 0), (0, 1), (1, 0), (1, 1)]
B = [(a[1], -a[0]) for a in A]

or more simply using tuple unpacking:

B = [(j, -i) for i, j in A]