fu.py

s = [0, 1]

for a in s:
    for b in s:
        for c in s:
            for d in s:
                if sum([a, b, c, d]) == 3 and \
                        (a == 0 or b == 0) and \
                        (b == 0 or a == 0) and \
                        (c == 0 or a == c) and \
                        (d == 0 or c == 1):
                    print a, b, c, d