How to Check if request.GET var is None?

Question

I'm getting into django and this is getting me a headache. I'm trying to get a simple GET variable. URL is site.com/search/?q=search-term

My view is:

def search(request):     if request.method == 'GET' and 'q' in request.GET:         q = request.GET.get('q', None)         if q is not None:             results = Task.objects.filter(                                    Q(title__contains=q)                                    |                                    Q(description__contains=q),                                    )             ...return...         else:             ...     else:         ... 

Search queries like mysite.com/search/? (without q) get through the first if correctly.

The problem is in queries like mysite.com/search/?q=. They don't get caught by if q is not None:

So, the short answer would be How can I check q == None? (I've already tried '', None, etc, to no avail.)

Answer 1

First, check if the request.GET dict contains a parameter named q. You're doing this properly already:

if request.method == 'GET' and 'q' in request.GET: 

Next, check if the value of q is either None or the empty string. To do that, you can write this:

q = request.GET['q'] if q is not None and q != '':     # Do processing here 

Notice that it is not necessary to write request.GET.get('q', None). We've already checked to make sure there is a 'q' key inside the request.GET dict, so we can grab the value directly. The only time you should use the get method is if you're not sure a dict has a certain key and want to avoid raising a KeyError exception.

However, there is an even better solution based on the following facts:

• The value None evaluates to False
• The empty string '' also evaluates to False
• Any non-empty string evaluates to True.

So now you can write:

q = request.GET['q'] if q:     # Do processing here 

See these other resources for more details:

• Python: Truth Value Testing
• Python: dict.get

Answer 2

Thanks for the clarification by @Ned. Found a complete explanation here.

Basically:

'==' can be thought of as "value equality", that is, if two things look the same, == should return a true value. (For those with a Java background, Python's == is actually doing something akin to an equals() method.)

'is' can be thought of as 'object identity', that is, if the two things actually are the same object.