Python Elements of list without substrings of another list

Question

I'm not a programmer, but I have a great desire to learn python. So, I hope you indulge me. My Problem: I need two new lists derived from lists A and B:

1. list elements with substrings in B (found in stackoverflow) and,

2. list elements without substrings in B. By the way, each time a new A list is produced in my app, elements without "B list substrings" can change in A list. New list can't have elements changed upper or lower case because I'll use their names the way they are.

A = ['EEG FP1-LE', 'EEG FP2-LE', 'EEG F3-LE', 'EEG F4-LE', 'EEG PG1-LE','EEG PG2-LE', 'EEG EKG-LE', 'PHOTIC PH']

B = ['Fp1', 'F3', 'Fp2','F4']

from How to compare two lists to keep matching substrings?

with_substrings =[[a for a in A if b in a][0] if any(b in a for a in A) else b for b in B]

print(with_substrings)  

returns:
['Fp1', 'EEG F3-LE', 'Fp2', 'EEG F4-LE'] # and thats great! 

However, I dont understand why 'EEG FP1-LE' and 'EEG FP2-LE' become 'Fp1' and 'Fp2', while 'EEG F3-LE' and 'EEG F4-LE' are the same.

Secondly, I need another list with elements without substrings in "B".

without_substrings = code??

without_substrings = ['EEG PG1-LE','EEG PG2-LE', 'EEG EKG-LE', 'PHOTIC PH']

I really appreciate any help and suggestions of a good list comprehension tutorial.