Python | Zip different sized list

• Last Updated : 13 Mar, 2023

In Python, zipping is a utility where we pair one list with the other. Usually, this task is successful only in the cases when the sizes of both the lists to be zipped are of the same size. But sometimes we require that different sized lists also to be zipped. Let’s discuss certain ways in which this problem can be solved if it occurs.

Method #1 : Using enumerate() + loop This is the way in which we use the brute force method to achieve this particular task. In this process, we loop both the list and when one becomes larger than other we cycle the elements to begin them from the beginning.

Python3

 `# Python3 code to demonstrate``# zipping of two different size list``# using enumerate() + loop` `# initializing lists``test_list1 ``=` `[``7``, ``8``, ``4``, ``5``, ``9``, ``10``]``test_list2 ``=` `[``1``, ``5``, ``6``]` `# printing original lists``print` `("The original ``list` `1` `is` `: " ``+` `str``(test_list1))``print` `("The original ``list` `2` `is` `: " ``+` `str``(test_list2))` `# using enumerate() + loop``# zipping of two different size list``res ``=` `[]``for` `i, j ``in` `enumerate``(test_list1):``    ``res.append((j, test_list2[i ``%` `len``(test_list2)]))` `# printing result``print` `("The zipped ``list` `is` `: " ``+`  `str``(res))`

Output:

```The original list 1 is : [7, 8, 4, 5, 9, 10]
The original list 2 is : [1, 5, 6]
The zipped list is : [(7, 1), (8, 5), (4, 6), (5, 1), (9, 5), (10, 6)]```

Method #2 : Using itertools.cycle() This is yet another way to perform this particular task, in this we cycle the smaller list so that it can begin zipping from beginning in case the smaller list gets exhausted using a zip function.

Python3

 `# Python3 code to demonstrate``# zipping of two different size list``# using itertools.cycle()``from` `itertools ``import` `cycle` `# initializing lists``test_list1 ``=` `[``7``, ``8``, ``4``, ``5``, ``9``, ``10``]``test_list2 ``=` `[``1``, ``5``, ``6``]` `# printing original lists``print` `("The original ``list` `1` `is` `: " ``+` `str``(test_list1))``print` `("The original ``list` `2` `is` `: " ``+` `str``(test_list2))` `# using itertools.cycle()``# zipping of two different size list``res ``=` `list``(``zip``(test_list1, cycle(test_list2))``            ``if` `len``(test_list1) > ``len``(test_list2)``            ``else` `zip``(cycle(test_list1), test_list2))` `# printing result``print` `("The zipped ``list` `is` `: " ``+`  `str``(res))`

Output:

```The original list 1 is : [7, 8, 4, 5, 9, 10]
The original list 2 is : [1, 5, 6]
The zipped list is : [(7, 1), (8, 5), (4, 6), (5, 1), (9, 5), (10, 6)]```

Approach

uses a while loop to iterate through both lists and create a zipped list of tuples. The algorithm first initializes two variables i and j to 0, representing the indices of the two lists. Then, an empty list is created to store the resulting tuples. The while loop checks whether i is less than the length of list1. If it is, it creates a tuple by taking the i-th element of list1 and the j-th element of list2 and appends it to the zipped list. Both i and j are incremented by 1. If i is greater than or equal to the length of list1, the loop is broken. If j is greater than or equal to the length of list2, it is reset to 0 to start again from the beginning of the shorter list. Finally, the resulting list of tuples is printed.

Algorithm

1. Initialize two variables, i and j, to 0.
2. Create an empty list to store the zipped tuples.
3. Use a while loop to iterate through the two lists.
4. If i is less than the length of list1, append a tuple of list1[i] and list2[j] to the zipped list and increment i and j.
5. If i is greater than or equal to the length of list1, break out of the loop.
6. If j is greater than or equal to the length of list2, set j to 0.

Python3

 `list1 ``=` `[``7``, ``8``, ``4``, ``5``, ``9``, ``10``]``list2 ``=` `[``1``, ``5``, ``6``]` `i ``=` `0``j ``=` `0``zipped_list ``=` `[]` `while` `True``:``    ``if` `i < ``len``(list1):``        ``zipped_list.append((list1[i], list2[j]))``        ``i ``+``=` `1``        ``j ``+``=` `1``    ``else``:``        ``break``    ``if` `j >``=` `len``(list2):``        ``j ``=` `0` `print``(``"The zipped list is:"``, zipped_list)`

Output

`The zipped list is: [(7, 1), (8, 5), (4, 6), (5, 1), (9, 5), (10, 6)]`

Time complexity: O(n), where n is the length of the longer list.
Auxiliary Space: O(n), where n is the length of the longer list.

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