Python 中用return {dict}[list] 这样的格式用什么作用，有何意义？

Question

def free(x,y):
return x 10 + y

def poi(n):
return {"0":0,"1":1,"2":2,"3":3,"4":4,"5":5:"6":6,"7":7,"8":8,"9":9}[n] #这句是怎么使用的？

i = input(">>>")
sint = s.split(".")
if i.find(".") == -1:
print(reduce(free,map(poi,"%s" % i)))
else:
a = reduce(free,map(poi,sint[0]))
b = reduce(free,map(poi,sint[1]))*0.1**len(sint[1])
print(a+b)

Answer 1

return {"0":0,"1":1,"2":2,"3":3,"4":4,"5":5:"6":6,"7":7,"8":8,"9":9}[n]
当n等于0的时候，上面的代码相当于
return "0":0
以此类推。