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Asked: 2026-06-18T04:46:30+00:00

I’m making a simple app on GAE that allows a user to enter a

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I’m making a simple app on GAE that allows a user to enter a url to an image and a name. The app then uploads this image to the Datastore along with its name.

After the upload the page self redirects and then should send the image back to the client and display it on their machine.

The app runs, but no image is shown. The log message I get is:

AttributeError: ‘NoneType’ object has no attribute ‘image’

The python:

import jinja2   # html template libary
import os

jinja_environment = jinja2.Environment(loader=jinja2.FileSystemLoader(os.path.dirname(__file__)))

import urllib   
import urllib2 
import webapp2

from google.appengine.ext import db
from google.appengine.api import urlfetch


class Default_tiles(db.Model):
  name = db.StringProperty()
  image = db.BlobProperty(default=None)


class MainPage(webapp2.RequestHandler):
  def get(self):

    # this just prints out the url which the user enters into input
    image_name = self.request.get('image_name') 

    template_values = {
        'image_name': image_name,
    }

    template = jinja_environment.get_template('index.html')
    self.response.out.write(template.render(template_values))



class Upload(webapp2.RequestHandler):
  def post(self):

    # get information from form post upload
    image_url = self.request.get('image_url') 
    image_name = self.request.get('image_name')

    # create database entry for uploaded image 
    default_tile = Default_tiles()
    default_tile.name = image_name
    default_tile.image = db.Blob(urlfetch.Fetch(image_url).content)
    default_tile.put()

    self.redirect('/')


class Get_default_tile(webapp2.RequestHandler):
  def get(self):
    name = self.request.get('image_name')
    default_tile = self.get_default_tile(name)

    self.response.headers['Content-Type'] = "image/png"
    self.response.out.write(default_tile.image)

  def get_default_tile(self, name):
    result = db.GqlQuery("SELECT * FROM Default_tiles WHERE name = :1 LIMIT 1", name).fetch(1)
    if (len(result) > 0):
      return result[0]
    else:
      return None


app = webapp2.WSGIApplication([('/', MainPage),
                               ('/upload', Upload),
                               ('/default_tile_img', Get_default_tile)],
                              debug=True)

The HTML:

<html>
    <head>
        <link type="text/css" rel="stylesheet" href="/stylesheets/main.css" />
    </head>

    <body>
        <form action="/upload" method="post">
            <div>
                <p>Name: </p>
                <input name="image_name">
            </div>
            <div>
                <p>URL: </p>
                <input name="image_url">
            </div>
            <div><input type="submit" value="Upload Image"></div>
        </form>
        <img src="default_tile_img?{{ image_name }}">

    </body>

</html>

Thanks for your help.

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1 Answer

  1. Editorial Team

    First of all, you need to send the GET parameter back to your MainPage handler. This should work if you put it in your Upload Handler, on the redirect line:

    self.redirect('/?image_name=%s' % image_name)

    That will ensure that MainPage knows what image we just uploaded.

    The second problem was just your <img> tag in your template. It should be this:

    <img src="default_tile_img?image_name={{image_name}}">

    I’ve tested it on my end after making these changes, and it works.

    Everything was fine it seems, except your GET parameters. Just remember that when you pass a GET request, you need to specify it’s name and value, so that the your app can get it correctly from the headers. As an example, if you wanted the header to specify what an image_name is, you would pass this URL:

    http://domain.com/?image_name=name

    Instead of:

    http://domain.com/?name

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