Reverse complement 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.