ndb and blobstore

[Pau]

Hi,

I have this model:

class Product(ndb.Model):

    title = ndb.StringProperty()

    description = ndb.TextProperty()

    img = ndb.BlobKeyProperty(indexed=False)

I need a html form that reads the values ​​of fields (title and description) and read the image (from a file field), and keeps the values ​​NDB object, the image in the Blobstore and updates the field BlobKeyProperty correctly.

As I work with wtforms, I tried to do it with a form like the following:

class ProductForm(Form):

    title = fields.TextField('Title', [validators.Required(), validators.Length(min=4, max=25)])

    description = fields.TextAreaField('Description')

    img = fields.FileField('img')

The form shows the file field correctly but in the POST, it does not work because I don't know how to read the file, save the file to Blobstore and update the BlobKeyProperty.

My handler is this:

class ProductHandler(BaseHandler):

    def new(self):

        if self.request.POST:

            data = ProductForm(self.request.POST)

            if data.validate():

                model = Product()

                data.populate_obj(model)

                model.put()

                self.add_message("Product add!", 'success')

                return self.redirect_to("product-list")

            else:

                self.add_message("Product not add!", 'error')

        params = {

            'form': ProductForm(),

            "kind": "product",

        }

        return self.render_template('admin/new.html', **params)

Error is Expected str, got u'image.jpg'

If someone can help me, I would appreciate it!

[Guido van Rossum]

You might get a quicker answer on StackOverflow.

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[Pau]

Thanks Guido.

I also posted the question on StackOverflow. See if there lucky.

Pau

2013/12/19 Guido van Rossum <gu...@python.org>

[Pau]

The only solution I found is to use a deprecated low-level API described in https://developers.google.com/appengine/docs/python/blobstore/#Python_Writing_files_to_the_Blobstore

I make a wtform validator for the FileField.

I changed:

img = fields.FileField('img')

To:

img = fields.FileField('img', [create_upload_file])

And I write this validator:

def create_upload_file(form, field):
    file_name = files.blobstore.create(mime_type=field.data.type, _blobinfo_uploaded_filename=field.data.filename)
    with files.open(file_name, 'a') as f:
        f.write(field.data.file.read())
    files.finalize(file_name)
    blob_key = files.blobstore.get_blob_key(file_name)
    field.data = blob_key

The validator create the blob in blobstore, and then it change the field data from FieldStorage to blob_key.

I don't think that is the best solution but it works for now.

[Patrick Costello]

If you want to avoid using the deprecated low-level API, you should upload the files to Google Cloud Storage instead: https://developers.google.com/appengine/docs/python/googlecloudstorageclient/. You can still serve them using blobstore: https://developers.google.com/appengine/docs/python/blobstore/#Python_Using_the_Blobstore_API_with_Google_Cloud_Storage.

Here you can see someone who did the same thing: http://stackoverflow.com/questions/20139095/moving-blobstore-to-gcs-google-app-engine-python

[Pau]

For now, I prefer to use the BlobStore because there are 5GB of free storage. and I have enough.

I guess in the future I will have to migrate to GCS, as you suggest me. But I see that it is a simple process.

Thanks for your reply and the links!

Pau

[Jakob Holmelund]

Def go with gcs. Totally fixed uploading on appengine and if you are under 5gb it will be dirt cheap anyways

[Pau]

Thanks Jakob for your advices!

2013/12/21 Jakob Holmelund <jakobho...@gmail.com>