How to break a compounded list

I have the following code I am trying to understand as I am new to Python. I understand that the code computes the powerset but the line subsetlist = [ subset + [item] for subset in result] is a little hard to understand. How can I break this compounded line to simple for loop for understanding.

def powerset(x):
    result = [[]]
    for item in x:
        subsetlist = [ subset + [item] for subset in result]
        result.extend(subsetlist)
    return result

This is what I have tried to make it simpler but it does not seem to work. My IDLE just gets stuck and does not print anything.

def powerset(x):
    result = [[]]
    for item in x:
        for subset in result:
            result.append(item)
    print(result)

You were very close. Just move the empty list creation inside the second loop.