Question

I am wondering, is there a way that i can store start and end values on my main method. I try doing this but it give me error:

def searchM():

    fileAddress = '/database/pro/data/'+ID+'.txt'
    with open(fileAddress,'rb') as f:
        root = etree.parse(f)
        for lcn in root.xpath("/protein/match[@dbname='M']/lcn")
            start = int(lcn.get("start"))#if it is PFAM then look for start value
            end = int(lcn.get("end"))#if it is PFAM then also look for end value
    return "%s, %s" % (start, end,)

values = searchM()

(start, end,) = values

The error message is UnboundLocalError: local variable ‘start’ referenced before assignment

Answer 1

The error you’re encountering is due to the start and end variables. Try initializing them first so that they exist in the even that a value is not set.

In addition, you are trying to create and return a string, which is then unpacked into two different variables.

Try the following:

def searchM():
    fileAddress = '/database/pro/data/%s.txt' % ID
    start = None
    end = None
    with open(fileAddress,'rb') as f:
        root = etree.parse(f)
        for lcn in root.xpath("/protein/match[@dbname='M']/lcn"):
            start = int(lcn.get("start")) #if it is PFAM then look for start value
            end = int(lcn.get("end")) #if it is PFAM then also look for end value
    return start, end

(start, end) = searchM()