riceissa

# Fencepost loop using dictionaries.
def inters_dict(lst):
    dct = {ch: True for ch in lst[0]}
    for s in lst[1:]:
        dct = {ch: True for ch in s if ch in dct}
    return dct.keys()

# I suspect Pythonistas would find the use of (ch, True) as key-value
# pairs to be jarring, so here it is using sets---essentially, the
# "True" part is implied by virtue of being in the set.