Deleting specific lists in python

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January 10th, 2013, 05:02 PM

Sam Hunter

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Deleting specific lists in python

Hi everyone

superlist=[[0,8],[1],[2],[3,6],[4],[5],[6,3,6],[7],[8,0,8],[9]]

I am trying to create a function on a list of lists that will do the following:

1) Deletes a repeat list( i.e. deletes a list that contains a number that has already been used in another list) from left to right so in the superlist (see above) it will identify that the first list contains a '0' and an '8' so any further list containing any of those two elements will be deleted. Therefore the penultimate list will be deleted.

So for the example above, if the function were called reduce() then, reduce(superlist) = [[0,8],[1],[2],[3,6],[4],[5],[7],[9]]

Thank you

January 10th, 2013, 08:57 PM

Nyktos

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This shouldn't be too hard to write, but your specification is a little vague as of now and needs to be clarified. In particular, the following questions came up for me when trying to implement this:

1. If one of the lists is deleted, should the numbers in that list still be added to the set of numbers seen? (For instance, given the list [[1], [1, 2], [2]], should the third entry be deleted?)

2. Is this meant to mutate the list in place, or create a new list?

I would also suggest against naming your function reduce, as there is a built-in function by that name in Python 2 (moved to the functools module in Python 3) that does something completely different.

January 11th, 2013, 06:10 AM

Sam Hunter

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Quote:

Originally Posted by Nyktos

Thanks.To answer the second question - i want to mutate it. To answer your first question, with the type of lists I will be working on it doesnt matter, because the repeated lists have all the numbers repeated.

An example of a list I will be working with:

[[1,2,3],[4],[2,2,3,1],[4], [5,8,9],[8,9,5,5,9]]

after the function is applied it will turn into:

[[1,2,3],[4],[5,8,9]]

Hope thats made it clearer.

Sam

January 11th, 2013, 03:04 PM

Nyktos

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Code:

def delete_duplicates(list_of_lists):
    numbers_seen = set()
    for idx, L in enumerate(list_of_lists):
        if any(item in numbers_seen for item in L):
            del list_of_lists[idx]
        else:
            numbers_seen.update(L)

Code:

>>> L = [[0, 8], [1], [2], [3, 6], [4], [5], [6, 3, 6], [7], [8, 0, 8], [9]]
>>> delete_duplicates(L)
>>> L
[[0, 8], [1], [2], [3, 6], [4], [5], [7], [9]]

January 12th, 2013, 10:38 AM

Sam Hunter

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Quote:

Originally Posted by Nyktos

Code:

def delete_duplicates(list_of_lists):
    numbers_seen = set()
    for idx, L in enumerate(list_of_lists):
        if any(item in numbers_seen for item in L):
            del list_of_lists[idx]
        else:
            numbers_seen.update(L)

Code:

>>> L = [[0, 8], [1], [2], [3, 6], [4], [5], [6, 3, 6], [7], [8, 0, 8], [9]]
>>> delete_duplicates(L)
>>> L
[[0, 8], [1], [2], [3, 6], [4], [5], [7], [9]]

Thanks a lot Nyktos

Deleting specific lists in python

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