'''data1.py

   Jed Yang, 2016-11-12

   Getting unique elements of a list.
'''

# Our own destructive function!
def removeDuplicates(array):
   '''Remove duplicated items in a list.'''
   for item in array:
      # count how many times the item occurs in array
      tally = array.count(item)
      if tally > 1:
         # remove the first occurrence of item in array
         array.remove(item)
   # return None to remind users of the destructive nature
   return None

digits = [3, 1, 4, 1, 5, 9, 2, 6, 5, 3, 5, 8, 9, 7, 9]
print('input:', digits)
result = removeDuplicates(digits)
print('input:', digits)
print('result:', result)
print()

print('======\n')

################################################################################

def getUniqueElements(array):
   '''Takes a *sorted* list as input.
      Returns a new list containing the unique elements of the input.
   '''
# As you read the code below, think about why I require array to be sorted.
   unique = []
   last = None
   for item in array:
      # What is going on here?
      if item == last:
         continue
      last = item
      unique.append(item)
   return unique

def test(array):
   print('input:', array)
   result = getUniqueElements(array)
   print('input:', array)
   print('result:', result)
   print()

test([1, 1, 1, 3, 3, 4, 4, 6, 6, 6])
test([1, 8, 1, 8, 1, 8])
test([4, 4, 4, 'apple', 'apple', 7, 7, 'apple', 4, 4, 4, 4, 4])

# Can you make sense of all the behaviour?  Explain ASAP (as simply as
# possible) what getUniqueElements() does when a list is not sorted.