反向补体DNA

Question

I have this equation for reverse complementing DNA in python:

def complement(s): 
    basecomplement = {'A': 'T', 'C': 'G', 'G': 'C', 'T': 'A'} 
    letters = list(s) 
    letters = [basecomplement[base] for base in letters] 
    return ''.join(letters)
def revcom(s):
    complement(s[::-1])
print("ACGTAAA")
print(complement("ACGTAAA"[::-1]))
print(revcom("ACGTAAA"))

however the lines:

print(complement("ACGTAAA"[::-1]))
print(revcom("ACGTAAA"))

do not equal one another. only the top line gives an answer. the bottom just prints "NONE"

any help why this is?

Answer 1

You forgot the return statement in revcom . Try this:

def revcom(s):
    return complement(s[::-1])

If you don't explicitly return a value from a function in Python, then the function returns None .

Answer 2

A pretty one liner to reverse complement a DNA sequence:

revcompl = lambda x: ''.join([{'A':'T','C':'G','G':'C','T':'A'}[B] for B in x][::-1])
print revcompl("AGTCAGCAT")

Answer 3

Python3, including whole IUPAC alphabet for nucleotides:

def revcomp(seq):
    return seq.translate(str.maketrans('ACGTacgtRYMKrymkVBHDvbhd', 'TGCAtgcaYRKMyrkmBVDHbvdh'))[::-1]

In Python2:

from string import maketrans

def revcomp(seq):
    return seq.translate(maketrans('ACGTacgtRYMKrymkVBHDvbhd', 'TGCAtgcaYRKMyrkmBVDHbvdh'))[::-1]

Answer 4

您需要从revcom() return结果。

Answer 5

`a = "AAAACCCGGT"
a= a[::-1]
print("reverse: "+a)
a = a.replace('A','a')
a = a.replace('T','A')
a = a.replace('a','T')
a = a.replace('C','c')
a = a.replace('G','C')
a = a.replace('c','G')
print("complement : "+a)`