testing for empty/null string in django
if your d is either None or "" then simply check -
if d: #do somethingelse: #do something else
Some empty fields return empty strings while others return None. A nullable boolean field however, will return False when it has been set. This will not pass the test in Srikar's answer. A more robust solution is this:
if d in [None, '']: # This field is empty.
myString is not a string -- it's a models.CharField. Show us your actual view where you're trying to do this.
If you've already got an instance of your model, you should just be able to do
if model_instance.myString:to test if it's not blank.