unusual django admin behavior when storing string values

Question

Using django trunk r13359 and django piston, I created a small restful service that stores string values.

This is the model I am using to store strings:

class DataStore(models.Model):
    data =  models.CharField(max_length=200)
    url = models.URLField(default = '', verify_exists=False, blank = True)

I used curl to post following data:

curl -d "data=somedata" http://localhost:8000/api/datastorage/

This is the code that handles storage as part of the django-piston handler

store = DataStore()
store.url = request.POST.get('url',""),
store.data = request.POST['data'],
store.save()
return {'data':store}

When I post the data with curl I get the following response body, which is expected:

{
    "result": {
        "url": [
            ""
        ], 
        "data": [
            "somedata"
        ], 
        "id": 1
    }
}

Whats not expected however is when I look at the stored instance from django admin, the value stored in the data field looks something like this:

(u'somedata',)

and the following is stored in the url:

('',)

Whats even more interesting is when I query the service with curl to see what is stored, I get the following:

{
    "result": {
        "url": [
            "('',)"
        ], 
        "data": [
            "(u'somedata',)"
        ], 
        "id": 1
    }
}

I'm stumped .. any ideas what could be going on?

Answer 1

Actually your response is also not what should be expected, note the [] around your strings, those shouldn't be there.

Your error is adding the comma after these two lines:

store.url = request.POST.get('url',""),
store.data = request.POST['data'],

Python will interprete you want to store a tuple in url and data, and django will convert those tuples to strings implicitly, resulting in the behaviour you see. Just remove the two commas and you'll be fine.