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Finding and grouping identical values ​​(float vectors) in nested lists

I have a list containing vectors (float x, y, z values) and I am trying to concatenate the same values ​​together.

Here's a working example in one list:

from collections import defaultdict

example_list = [1,5,1,4,2,5,5,4,5,7,2,1,7,9] 

d = defaultdict(list)

for item in example_list:
     d[item].append(item)

groupedlist = sorted(d[x] for x in d)

# Returns [[1, 1, 1], [2, 2], [4, 4], [5, 5, 5, 5], [7, 7], [9]]

I am trying to achieve the same result for nested lists of 3D vectors (X, Y, Z) ...

example_vectorlist = [[1,2,4], [1,2,3], [3,4,3], [1,3,2], [5,6,7], [3,4,3], [5,6,7]]

# Desired output = [[1,2,4],[[1,2,3],[1,2,3]],[1,3,2],[[3,4,3], [3,4,3]],[[5,6,7], [5,6,7]]
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3 answers


Just put the keys for defaultdict

in tuples:

from collections import defaultdict

example_list = [[1,2,4], [1,2,3], [3,4,3], [1,3,2], [5,7,1], [3,4,3], [5,6,1]]

d = defaultdict(list)

for item in example_list:
    d[tuple(item)].append(item)

groupedlist = sorted(d[x] for x in d)


The problem with using only the original "vectors" as keys to d

is that lists are not hashable; whereby their tuples address this.

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Without use defaultdict

:



example_vectorlist = [[1,2,4], [1,2,3], [3,4,3], [1,3,2], [5,7,1],[3,4,3], [5,6,1]]
d = {}
for el in example_vectorlist:
    try:
        d[tuple(el)].append(el)
    except KeyError:
        d[tuple(el)] = [el]
print d.values()
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Your desired output does not reflect what you have in the input, if you want to group the common sublists you can use itertools.groupby

assuming you want to sort the output with a dict and then sorting makes less sense than just creating groups from the sorted list using groupby:

from itertools import groupby

print([list(v) for _,v in groupby(sorted(example_vectorlist))])

Whichever source list for you outputs the same:

example_list = [1,5,1,4,2,5,5,4,5,7,2,1,7,9]
print([list(v) for _,v in groupby(sorted(example_list))])
[[1, 1, 1], [2, 2], [4, 4], [5, 5, 5, 5], [7, 7], [9]]
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