# Creation
set1 = set()              #  empty set (do not use {}, it's a dict !)
set2 = {3, 5, 2, 1};      # {1,2,3,5}

for i in set2:
   print(i)

# Insert
set2.add(3)
set2.add(4)

print(set2)

# remove
try:
  set2.remove(0)
except KeyError:
  print("0 not in set2")

set2.remove(4)

print(set2)

# test

if 0 in set2:
   print("0 is in set2")
else:
   print("0 is NOT in set2")

if 3 in set2:
   print("3 is in set2")
else:
   print("3 is NOT in set2")

# Advanced set operations

set1 = {5,6,7}

# Union
out = set1.union(set2)

print(out)

# Intersection
out = set1.intersection(set2)

print(out)

# Difference (set2 - set1)
out = set2.difference(set1)

print(out)