Find the longest palindrome substring of a piece of DNA I have to make a function that prints the longest palindrome substring of a piece of DNA. I already wrote a function that checks whether a piece of DNA is a palindrome itself. See the function below.

def make_complement_strand(DNA):
    complement=[]
    rules_for_complement={"A":"T","T":"A","C":"G","G":"C"}
    for letter in DNA:
        complement.append(rules_for_complement[letter])
    return(complement)

def is_this_a_palindrome(DNA): 
        if DNA!=(make_complement_strand(DNA)[::-1]):     
            print("false")                  
            return False
        else:                             
            print("true")
            return True

is_this_a_palindrome("GGGCCC") 


But now: how to make a function printing the longest palindrome substring of a DNA string?

The meaning of palindrome in the context of genetics is slightly different from the definition used for words and sentences. Since a double helix is formed by two paired strands of nucleotides that run in opposite directions in the 5’- to-3’ sense, and the nucleotides always pair in the same way (Adenine (A) with Thymine (T) for DNA, with Uracil (U) for RNA; Cytosine (C) with Guanine (G)), a (single-stranded) nucleotide sequence is said to be a palindrome if it is equal to its reverse complement. For example, the DNA sequence ACCTAGGT is palindromic because its nucleotide-by-nucleotide complement is TGGATCCA, and reversing the order of the nucleotides in the complement gives the original sequence.
Longest palindromic substring is a computer science problem.

One common solution is Manacher's algorithm.