Question

I am implementing a one off data importer where I need to search for existing slugs. The slugs are in an array. What is the accepted best practices way of converting an array to an OR query?

I came up with the following, which works, but feels like way too much code to accomplish something this simple.

# slug might be an array or just a string
# ex:
slug = [ "snakes", "snake-s" ] # in the real world this is generated from directory structure on disk

# build the query
query = MyModel.objects
if hasattr(slug, "__iter__"):
    q = Q()
    for s in slug:
        q = q.__or__(Q(slug=s))
    query = query.filter(q)
else:
    query = query.filter(slug=slug)

Answer 1

slug = ["snakes", "snake-s" ] # in the real world this is generated from directory structure on disk

# build the query
query = MyModel.objects
if hasattr(slug, "__iter__"):
    q_list = []
    for s in slug:
        q_list.append(Q(slug=s))
    query = query.filter(reduce(operator.or_, q_list))
else:
    query = query.filter(slug=slug)

• q_list = [] create a list of Q clauses
• reduce(operator.or_, q_list) implode the list with or operators

read this: http://www.michelepasin.org/techblog/2010/07/20/the-power-of-djangos-q-objects/

@MostafaR – sure we could crush my entire codeblock down to one line if we wanted (see below). Its not very readable anymore at that level though. saying code isn’t “Pythonic” just because it hadn’t become reduced and obsfucated is silly. Readable code is king IMHO. Its also important to keep in mind the purpose of my answer was to show the reduce by an operator technique. The rest of my answer was fluff to show that technique in context to the original question.

result = MyModel.objects.filter(reduce(operator.or_, [Q(slug=s) for s in slug])) if hasattr(slug, "__iter__") else MyModel.objects.filter(slug=slug)