Compare list element with multiple list elements

Question

I have two lists:

targets = [ [ [4.88], [2.76], [0.4] ], [ [2.6], [2.12], [7.4], [0.2] ] ]
multiples = [ [ [4.2, 3.6, 6.3], [3.5, 2.5], [7.3, 0.5] ], [ [3.6, 0.3], [5.2, 8.6, 3.7], [3.6, 0.4], [2.3, 6.4] ] ]

For every entry in the first list, there are multiple entries in the second one. Now I want to compare these numbers and count the accurences of the numbers that are lower than the traget number. I tried the following, but I don't know how I can compare one single value with multiples and how to refer simultaniously to them.

for element in targets:
    tmp = []
    for item in element:
        tmp2 = []
        if item > multiples

The output should be something like this:

[ [ [2], [1], [0] ], [ [1], [0], [2], [0] ] ]

Does somebody know a solution?

Answer 1

One solution using zip() and sum() :

targets = [ [ [4.88], [2.76], [0.4] ], [ [2.6], [2.12], [7.4], [0.2] ] ]
multiples = [ [ [4.2, 3.6, 6.3], [3.5, 2.5], [7.3, 0.5] ], [ [3.6, 0.3], [5.2, 8.6, 3.7], [3.6, 0.4], [2.3, 6.4] ] ]

out = []
for val1, val2 in zip(targets, multiples):
    out.append([[sum(i < j for i in vval2) for j in vval1] for (vval1, vval2) in zip(val1, val2)])

print(out)

Prints:

[[[2], [1], [0]], [[1], [0], [2], [0]]]

Answer 2

you wrote: 'For every entry in the first list' . So i think you have nested your lists to deep... i flattened your lists a bit and did:

targets_flat = [
    4.88, 2.76, 0.4,
    2.6, 2.12, 7.4, 0.2
]
multiples_flat = [
    [4.2, 3.6, 6.3], [3.5, 2.5], [7.3, 0.5],
    [3.6, 0.3], [5.2, 8.6, 3.7], [3.6, 0.4], [2.3, 6.4]
]

for ref, valuelist in zip(targets_flat, multiples_flat):
    lower = [v for v in valuelist if ref > v]
    print("reference: {} -> lower: {}".format(ref, lower))

If the deep nested lists are your intention so you must flatten the lists ( see here an example )

Answer 3

In [4]: [[[len([v for v in vals if v < tg[0]])] for vals, tg in zip(mult, tl)] for mult, tl in zip(multiples, targets)]
Out[4]: [[[2], [1], [0]], [[1], [0], [2], [0]]]

The zip built-in function is ideal to iterate over multiple lists. The proposed solution heavily relies on it zipping recursively your lists of lists. While it is a one-liner it is certainly not the most readable solution to your problem.

Note : The [] around len() is really just to match with the desired output. If you omit it you get:

In [5]: [[len([v for v in vals if v < tg[0]]) for vals, tg in zip(mult, tl)] for mult, tl in zip(multiples, targets)]
Out[5]: [[2, 1, 0], [1, 0, 2, 0]]