a={1,3,4,5,1}
print(type(a))
print(len(a))             #set ignore the empty set
d28dac82f5b62cda04acd97fd4d717753b251ffb
<mask token>

<mask token>
print(type(a))
print(len(a))

a = {1, 3, 4, 5, 1}
print(type(a))
print(len(a))

a={1,3,4,5,1}
print(type(a))
print(len(a))             #set ignore the empty set