Django/Python - Try/except problem

Question

Hello, i have code like this:

try:
            var = request.POST['var']                                        
except NameError:                
            var = ''

Why always code after "except" is executing? Even if request.POST['var'] exist.

Answer 1

How do you know it is executing? Perhaps request.POST['var'] is also '' so you couldn't tell the difference.

Also, the only way that

var = request.POST['var'] 

could raise a NameError is if request doesn't exist.

If request.POST doesn't exist, means POST doesn't exist as an attribute of request thus raising AttributeError instead, and if request.POST['var'] doesn't exist, means 'var' is not a key of request.POST thus raising KeyError instead.

---

EDIT:

My guess is that you're not sending a POST. But can't know for sure.

Answer 2

A better way to do what you seem to be trying to do might be

var = request.POST.get('var', 'some default value')

where the second argument to the POST dict's get method is the value to return if the key ('var' in this case) doesn't exist. Translating your example exactly would result in:

var = request.POST.get('var', '')

That way, no try...except block or conditional statements are needed.

Answer 3

Eliminate the guesswork and replace NameError with something like KeyboardInterrupt, look at the traceback and you'll know exactly what the problem is.

Answer 4

what's the result of the following in your case?

except NameError, e:
    print e

Answer 5

try

try:
            if request.method == 'POST':
               var = request.POST['var']                                        
except NameError:                
               var = ''