Question

I have a function that gets an image from a form, and put’s it into the database along with the username. So, here is my database:

class Imagedb(db.Model):
    name = db.StringProperty(required = True)
    image = db.BlobProperty()

And here is the code that writes to the database:

class Change_Profile_Image(MainHandler):
    def get(self):
        if self.user:
            self.render('change_profile_image.html', username = self.user.name, firstname=self.user.first_name)
        else:
            self.render('change_profile_image.html')

    def post(self):
        imagedb = Imagedb(name = self.user.name)
        imageupl = self.request.get("img")
        imagedb.image = db.Blob(imageupl)
        imagedb.put()
        self.redirect('/profile')

Any who, it works awesome. Except for one thing. What i’m trying to accomplish is only storing ONE profile picture. What ends up happening is this:

Say I am the user admin. Ill upload a display pic, that pic shows in the profile. Ill upload another one, that one shows. Cool, except for the fact that I have 2 objects in my database that have the name = admin attribute. I would like to edit this…

    def post(self):
        imagedb = Imagedb(name = self.user.name)
        imageupl = self.request.get("img")
        imagedb.image = db.Blob(imageupl)
        imagedb.put()
        self.redirect('/profile')

so that I can post images to the database, but if one exists, it is overwritten. Could anyone help me with this please? I’m relatively new to python and app engine.

If something is unclear, please let me know.

Answer 1

You want to set the key of the Imagedb entity to “name”. Essentially, you don’t need the name field, but you’ll instantiate it like

imagedb = Imagedb(key_name = self.user.name)

The key is a required field on all entities. By using your user name as the key it means every time you refere to a given key, it’s the same entity.