Vfrdtyky

Need a little help for a project.

I have two lists each containing 4 or more specific weeks -
True_SH:

[Timestamp('2012-01-08 00:00:00'), Timestamp('2012-04-22 00:00:00'), Timestamp('2012-08-19 00:00:00'), Timestamp('2012-10-07 00:00:00')

True_SL:

[Timestamp('2011-11-20 00:00:00'), Timestamp('2012-03-25 00:00:00'), Timestamp('2012-05-13 00:00:00'), Timestamp('2012-09-02 00:00:00')

They alternate and it is not possible to have two SL or SH one after the other, in this example:

SL->SH->SL->SH->SL->SH->SL->SH

How to output the distance in weeks between the dates in a third list BUT with the following rule - the distance from SL to SH produces the positive number and the distance from SH to SL outputs the negative number of weeks? The number should include the start and end week in the count.

In this example distance from first two:
(1st)SL('2011-11-20 00:00:00') to (2nd) SH('2012-01-08 00:00:00') outputs positive 7, -> distance from 2nd(SH) to (3rd) SL('2012-03-25 00:00:00') outputs NEGATIVE -10 , then from 3rd(SL) to 4th(SH) outputs a positive number again and then from SH to SL negative and so on.

I need this list to further analyze if there are repeating sequences.

Really hope anyone can help me as I am struggling to find a way to do that.

Thanks!

My approach is to merge the two arrays, sort the merged array, then iterate over the merged array to calculate the number of weeks between neighbouring dates. You can then test the larger of the two neighbouring dates to see which of the original lists it came from, and return a negative value if it came from the true_sl list.

Note that my choice to sort the merged lists assumes that the dates in the true_sh and true_sl lists will always interleave.

Here's the code:

from datetime import datetime





true_sh = [datetime(2012, 1, 8), datetime(2012, 4, 22), datetime(2012, 8, 19), datetime(2012, 10, 7)]

true_sl = [datetime(2011, 11, 20), datetime(2012, 3, 25), datetime(2012, 5, 13), datetime(2012, 9, 2)]



out_array = true_sh

out_array.extend(true_sl)

out_array.sort()



for i, elem in enumerate(out_array):

    if i == 0:

        continue



    num_days = elem - out_array[i - 1]

    num_weeks = num_days.days // 7

    if elem in true_sl:

        num_weeks = -num_weeks



    print(num_weeks)

And here's the output:

7

-11

4

-3

14

-2

5

Note also that you gave the expected 2nd output as -10, but there are 77 days between 8th Jan 2012 and 25th Mar 2012, so I believe that the output here of -11 is correct. Can you confirm, please?