L = [1, 2]
L = L + [3] # concatenate: slower
print L
L.append(4) # faster, but in-place
print L
L = L + [5, 6] # concatenate: slower
print L
L.extend([7, 8]) # faster, but in-place
print L
L += [9, 10] # mapped to L.extend([9, 10])
print L