flatten.py

input = [[1,2,[3]],4, [5], [[[[6],7], 8]]]

def flatten(input, flattened):
    for e in input:
        if type(e) == list:
            flatten(e, flattened)
        else:
            flattened.append(e)
    return flattened


print("input: " + str(input))
output = flatten(input, [])
print("output: " + str(output))
fail = False
for e in output:
    if type(e) == list:
        print("fail: array not flattened")
        fail = True
        break

if fail:
    print("Testing failed")
else:
    print("All tests passed")