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Python Python Collections (Retired) Tuples Combo

R W
R W
19,894 Points
Posted by R W
R W
19,894 Points

Having trouble utilizing 'Enumerate' in Python Collections challenge 'Combo'

I am trying to complete the 'Combo' challenge but when I run my code, it prints out everything three times and, despite working on it all day, I cannot for the life of me figure out how to make it not do that. I suspect that it prints each thing three times due to the use of two for-loops but this is my best attempt so far; nothing else has gotten me this close.

I would prefer to avoid using methods like 'zip' for now and stick with what has been taught in the course.

Any help would be greatly appreciated!!

zippy.py 
# combo(['swallow', 'snake', 'parrot'], 'abc')
# Output:
# [('swallow', 'a'), ('snake', 'b'), ('parrot', 'c')]
# If you use list.append(), you'll want to pass it a tuple of new values.
# Using enumerate() here can save you a variable or two.
def combo(it1, it2):
    enum_list = list()
    for num, item in enumerate(it1):
        for j1, j2 in enumerate(it2):
            enum_list.append((item, j2))
    return enum_list

3 Answers

Seth Kroger
Seth Kroger
56,413 Points
Seth Kroger
Seth Kroger
56,413 Points

Because the for loops are nested inside each other it will take the first item of the first list and combine it with every item of the second, then take the second item and combine it with every item of the second list, and so on. So you only want to have one for loop and find the corresponding item in the second list to combine the two. My quick and dirty solution:

def combo(iter1, iter2):
  result = []
  iter2_as_list = list(enumerate(iter2))
  for i, item1 in enumerate(iter1):
    j, item2 = iter2_as_list[i]
    result.append((item1, item2))
  return result
Rodrigue Loredon
Rodrigue Loredon
1,338 Points
Rodrigue Loredon
Rodrigue Loredon
1,338 Points

Thanks R W, Dan and Seth. Thanks to your insights I was able to achieve the challenge with my code written as follows:

iter1 = ['swallow', 'snake', 'parrot']
iter2 = 'abc'

def combo(iter1,iter2):

  final_list = []

  iter2_as_list = list(iter2)

  for i, item1 in enumerate(iter1):

    item2 = iter2_as_list[i]

    final_list.append((item1,item2))

  return final_list
Dan Johnson
Dan Johnson
40,533 Points
Dan Johnson
Dan Johnson
40,533 Points

Since we're associating elements from each iterable by their index, you can get away with just using enumerate once. 

def combo(iter1, iter2):
  zipped = []

  # The challenge states that the iterables will be
  # of the same length so we don't have to worry about
  # validation.

  # for the index and value in the enumerated iterable
    # Append a new tuple with the first value being the pulled in
    # from the for loop, and the other by using the index
    # to access the value in the second iterable

  return zipped

When you call enumerate, each tuple is in the form (index, value_at_index) where index starts at 0 by default.

You could implement a similar solution using range.