d={'a-b':[1,2,3],'c-d':[4,5,6]}

{'a': [1, 2, 3], 'b': [1, 2, 3], 'c': [4, 5, 6], 'd': [4, 5, 6]}

d={'a-b':[1,2,3],'c-d':[4,5,6]}
newd={}
for k,v in d.items():
    newd[k.split('-')[0]]=v
    newd[k.split('-')[1]]=v
print(newd)
#{'a': [1, 2, 3], 'b': [1, 2, 3], 'c': [4, 5, 6], 'd': [4, 5, 6]}

for k,v in d.items():
    x, y = k.split("-")
    newd[x]=v
    newd[y]=v