Question

I have implemented this algorithm:

def get_hot_pages(self, radius = 2):
    if self.page == None or self.max_pages == None: return []
    hot_pages = []
    for page in xrange(self.page - radius, self.page + radius + 1):
        if page < 0 or page >= self.max_pages : continue
        hot_pages.append(page)
    return hot_pages

But something tells me this can be implemented better. Is there a more pythonic way to do this?

Answer 1

The usual “trick” is to use max() and min() in order to set the minimum and maximum page numbers:

def get_hot_pages(self, radius = 2):
    if self.page is None or self.max_pages is None: return []
    return range(max(self.page-radius, 0), min(self.page+radius+1, self.max_pages))

The main advantages of this approach are:

• People who know this standard procedure understand immediately what the code does (only one line to read). There is no need to read a whole loop block (which contains a filter test) in order to understand that some pages can be out of bound.
• This is efficient: there is no test inside a loop that runs at every iteration and filters out incorrect page numbers. It is generally good to keep an eye on efficiency (even if it does not matter here, it may matter in other situations): it often happens that a solution be at the same time simple, legible and quite efficient (i.e., looking for efficiency can actually make the code more legible, because it forces one to isolate the essence of the problem at hand).