寻找一段DNA的最长回文子串

Question

我必须做一个函数，它可以打印出DNA片段中最长的回文子串。我已经写了一个函数来检查一段DNA本身是否是回文。请参见下面的函数

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

is_this_a_palindrome("GGGCCC") 

但是现在：如何使函数打印DNA字符串的最长回文子字符串

回文在遗传学背景下的含义与单词和句子的定义略有不同。由于双螺旋是由5'-3'方向相反的两条成对核苷酸链组成的，并且核苷酸总是以相同的方式配对（腺嘌呤（a）和胸腺嘧啶（T）用于DNA，尿嘧啶（U）用于RNA；胞嘧啶（C）和鸟嘌呤（G）），a（单链）核苷酸序列若等于其反向补体，则称为回文序列。例如，DNA序列ACCTAGGT是回文的，因为它的核苷酸补体是TGGATCCA，而颠倒补体中核苷酸的顺序会得到原始序列

Answer 1

在这里，这应该是获得最长回文子字符串的合适起点

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


def longest_palindrome_ss(org_dna, palindrone_func):
    '''
    Naive implementation-

    We start with 2 pointers.
    i starts at start of current subsqeunce and j starts from i+1 to end
    increment i with every loop

    Uses palindrome function provided by user

    Further improvements- 
    1. Start with longest sequence instead of starting with smallest. i.e. start with i=0 and j=final_i and decrement.
    '''
    longest_palin=""
    i=j=0
    last_i=len(org_dna)
    while i < last_i:
        j=i+1
        while j < last_i:
            current_subsequence = org_dna[i:j+1]
            if palindrone_func(current_subsequence):
                if len(current_subsequence)>len(longest_palin):
                    longest_palin=current_subsequence
            j+=1
        i+=1
    print(org_dna, longest_palin)
    return longest_palin


longest_palindrome_ss("GGGCCC", is_this_a_palindrome)
longest_palindrome_ss("GAGCTT", is_this_a_palindrome)
longest_palindrome_ss("GGAATTCGA", is_this_a_palindrome)

以下是一些处决-

mahorir@mahorir-Vostro-3446:~/Desktop$ python3 dna_paln.py 
GGGCCC GGGCCC
GAGCTT AGCT
GGAATTCGA GAATTC