# Exercise 13:
# Write a function that takes a list and returns a new list that contains 
# all the elements of the first list minus duplicates.

# this one uses a for loop
def dedupe_v1(x):
  y = []
  for i in x:
    if i not in y:
      y.append(i)
  return y

#this one uses sets
def dedupe_v2(x):
    return list(set(x))

a = [1,2,3,4,3,2,1]
print a
print dedupe_v1(a)
print dedupe_v2(a)