Swapping Two Elements Between Two Lists In Python

I'm trying to swap elements between two lists, and python doesn't seem to let that happen. def swap(A,B,i,j): TEMP_B = B[j] B[j] = A[i] A[i] = TEMP_B return A,B X

Solution 1:

You can use .copy() if working on NumPy arrays:

def swap(A,B,i,j):
    TEMP_B = B[j].copy()
    B[j] = A[i]
    A[i] = TEMP_B
    return A,B

Should work on 1d or 2d arrays.

A = np.arange(5)
B = np.arange(5, 10)
swap(A, B, 1, 1)
# (array([0, 6, 2, 3, 4]), #  array([5, 1, 7, 8, 9]))

Solution 2:

This does not come from your swap function that works with regular arrays It has to do with the fact that you are using numpy.array.

Here is a similar question I found.

You need to do TEMP_B = np.copy(B[j]) since Numpy copies data lazily.

Solution 3:

l1 = [1, 2, 3]
l2 = ['a', 'b', 'c']

print(l1, l2)
l1[1], l2[2] = l2[2], l1[1]
print(l1, l2)

in essence:

list1[i], list2[j] = list2[j], list1[i]a, b = b, a