superstring.py

#!/usr/bin/python

from collections import OrderedDict

value,key="",""
s=OrderedDict({})

with open("rosalind_long.txt","rU") as f:
    for x in f:
        if x[0]!=">":
            value=value+x.strip()
        else:
            if key!="": s[key]=value
            key=x[1:].strip()
            value=""
    s[key]=value

strs=s.values()
while len(strs)>1:
    h=strs.pop()
    print len(h)
    k=h[0:400]
    for i,x in enumerate(strs):
        j=x.find(k)
        if j>=0:
            if len(h)+j>len(x):
                strs[i]=x[0:j]+h
            strs.insert(0,strs.pop(i))
            break
    else:
        strs.insert(0,h)

print strs[0]