Remove items from a nested list based on comparing values obtained from another nested list

Question

I have two nested lists in the form:

---

a = [[1,2,3,4,5],[3,4,5,6,7,8,9],[5],[1,2,3,6,7,8,9]]
b = [[1,4],[6,9]]

I want a function that will take these two lists, use the values in each sublist of list b and use that to delete values in list a so that the output looks like this :

[[5],[5],[5],[]]

i.e. function should iterate all values in list a and remove values such that 1 <= value <= 4 and 6 <= value <= 9

At present I have this :

def remove_unnecessary_peaks(peaks_total,peaks_to_be_excluded):
    redacted_peak_list = peaks_total.copy()
    i=0
    for  item in peaks_total:
        for value_set in peaks_to_be_excluded:
            for peak in item:
                #print (value_set[0],peak,value_set[1])
                if value_set[0]<=peak<=value_set[1]:
                    redacted_peak_list[i].remove(peak)
        i=i+1          

    return (redacted_peak_list)                

a = [[1,2,3,4,5],[3,4,5,6,7,8,9],[5],[1,2,3,6,7,8,9]]
b = [[1,4],[6,9]]

print(remove_unnecessary_peaks(a,b))

I have made a copy of the data by doing redacted_peak_list = peaks_total.copy() so that I don't modify the peaks_total variable as it will screw up the indexing. In Spyder's debug mode I see that the variable peak is not being indexed properly, I see it skipping numbers from sublist a.

My output is [[2, 4, 5], [4, 5, 7, 9], [5], [2, 7, 9]] whereas I want [[5],[5],[5],[]]

Answer 1

You can use a list comprehension like this:

[[i for i in s if not any(l <= i <= h for l, h in b)] for s in a]

This returns:

[[5], [5], [5], []]