程序代码：

d2e={1:"one",2:"two",3:"three",4:"four",5:"five",6:"six"}

print(d2e)

print(d2e[5])

e2d={}

for key,val in d2e.items():
    e2d[val]=key
print(e2d)

s=list(e2d.keys())
print(s)

s=''.join(s)
print(list(s))

m=set(tuple(list(s)))

print(m)