def invert(dic):
rd = {}
for k,v in dic.items():
if v in rd:
raise KeyError
rd[v] = k
return rd
print(invert({"a":"z","b":"y","c":"x"}))
print(invert({"a":"z","b":"y","c":"z"}))
def favorite_color(dic):
rd = {}
for k,v in dic.items():
rd[v] = rd.get(v,0) + 1
m = max(rd.items(),key=lambda x: x[1])[0]
return m
print(favorite_color({"Marc":"yellow", "Ezri":"blue", "Kris":"blue"}))
def count(li):
rd = {}
for v in li:
if v in rd:
rd[v] += 1
else:
rd[v] = 1
return rd
print(count(['a','b','a','b']))
或者
def count(li):
rd = {}
for v in li:
rd[v] = rd.get(v,0) + 1
return rd
print(count(['a','b','a','b']))
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