# Change 1
#A = list [9, 2, 7, 5, 4,100,50,32,33]
A = [9, 2, 7, 5, 4,100,50,32,33]
def quick_sort (A):
    n = len (A)
    if n<= 1:
        return A
    pivot = A [0]
    right = []
    left = []
    for i in range (1, n):
        if A [i]<= pivot:
            left.append (A [i])
        else:
            right.append (A [i])
    R = quick_sort (right)
    L = quick_sort (left)
    #Change 2
    #return L + pivot + R
    return L + [pivot] + R
print (quick_sort (A)) # =>[2, 4, 5, 7, 9, 32, 33, 50, 100]

The changes are as commented.
I think that an error message was displayed when you executed the original code, so check the contents of the error message against the changes.