```
class Solution(object):
def findRepeatedDnaSequences(self, s):
return [k for k,v in collections.Counter(s[i:i+10] for i in range(len(s))).iteritems() if v>1]
```

Or if you want to do a little less work:

```
class Solution(object):
def findRepeatedDnaSequences(self, s):
return [k for k,v in collections.Counter(s[i:i+10] for i in range(len(s)-9)).iteritems() if v>1]
```