Match all strings from list A to every strings from list B

Question

I am looking for help in writing a script (preferably python), to compare two lists. The task:

I have list of filenames in file a.txt: Example:

ABC
BCD
DEF
EDC

and a strings list in list b.txt:

A
B
C
D
E
F
G

what I want script to do is "compare" those two lists and output result to file result.txt, where I can have every string from list a next to all matches of list b.txt so, for example, result.txt would look like for the above lists:

ABC|A,B,C
BCD|B,C,D
DEF|D,E,F
EDC|E,D,C

I might add, both lists are quite big, list a has 60k rows, list b few k.

Would appreciate the help a lot! thanks

Answer 1

1. Build lists A_list , B_list from datafiles

2. Write the result file looping over the filenames ( a ) provided by first list ( A_list )

   • build the matches list of the elements ( b ) of the second list ( B_list ) that are in the a element
   • optionally skip the end of the loop if you do not want a result when there is no match
   • write the result line for filename joining the matches

with open("a.txt", 'r') as f:
    A_list = f.read().splitlines()
with open("b.txt", 'r') as f:
    B_list = f.read().splitlines()
    
with open('result.txt', 'w') as f:
    for a in A_list:
        matches = [b for b in B_list if b in a]
        if not matches: continue  # optional
        f.write(f"{a}|{','.join(matches)}\n")