I am trying to use lambda do to some sorting on a list. What I wanted to do is sort the coordinates based on their manhattan distance from an inital poisition. I know I have most of the syntax down but it seems like I am missing something small, Thanks!
while (len(queue) > 0):
queue.sort(queue, lambda x: util.manhattanDistance(curr,x))
It appears that you're trying to tell the sort() method to use your lambda function as the key for sorting. This is done with the keyword argument key:
queue.sort(queue, key = [your lambda function])
The rewritten line is:
queue.sort(queue, key = lambda x: util.manhattanDistance(curr,x))
EDIT: misunderstood the purpose of the original lambda function; thought it was intended as a comparison function, which doesn't make sense since distance functions can't be negative
lambda as a cmp function, and that's exactly why it's not working. (In Python 3, the code would actually work as written.)
2to3 won't fix this problem), it's also much easier to read. Nobody remembers what the order is. The only reason to ever use a cmp function without a keyword is if you need to be compatible with Python 2.3 or earlier.
x represents each element, and the function itself returns the value associated with that element for the purpose of sorting the list.
while len(queue) > 0:. But, since 0 is false and any other integer is not, this is identical towhile len(queue):. And, since an empty sequence is false and any other sequence is not, this is identical towhile queue:. And that's how you should write it—it's more idiomatic, easier to read, shorter, and possibly even more efficient.queueas the first argument toqueue.sort. Whatever typequeueis, that's not right. (Oh, and don't call a variablequeue; that's the name of a standard library module.)sortis not going to change the length of the object, so this is just going to loop forever, re-sorting an already-sorted list over and over.