Django Update 1.6 to 1.9 – 1.8 to 1.9

Upgrading DJango from 1.8 to 1.9 was relatively easier as the main pain of upgrading DRF was all dealt with when I was upgrading Django from 1.6 to 1.8, which has been discussed here. A lot of libraries has to be updated which I came to know as and when I tried running the application.

One of the main issues that I had while the whole upgrade was creating the migration from scratch. The project had South for managing the migration, but since Django has now its inbuilt support, I removed this South and all the existing migration files. There were some circular dependency issues when creating the new migration. You may get an error as below.

django.db.migrations.graph.CircularDependencyError: partner.0001_initial, address.0001_initial, users.0001_initial

The reason was with some of the foreign keys. Django internally creates a graph data structure to figure out this dependency. You can get rid of it by removing the foreign keys temporarily, running the migrations and then creating the keys again.

These following libraries had to go for an update, mentioned with the version that I am using with the Django version 1.9:

Django Reversion 1.10.0, Django tables 2 1.0.5, Django Mptt 0.8.0,  Django Celery 3.2.1, Django Extensions 1.7.3, Django Haystack 2.5.1, Django Redis Cache 1.7.1, Django Redis Session 0.5.6

There are setting changes around the library – Pipeline. You can find the changes to be done on the library’s documentation page. The new settings are as such:

"STATICFILES_FINDERS - 'pipeline.finders.PipelineFinder', 
 PIPELINE = {
    'PIPELINE_ENABLED': True,
    'JAVASCRIPT': {
        'stats': {
            'source_filenames': (
              'js/jquery.js',
              'js/d3.js',
              'js/collections/*.js',
              'js/application.js',
            ),
            'output_filename': 'js/stats.js',
        }
    }
}"

Other than this, there were some code changes which were introduced in Django 1.9, for which I had to change some import statements. Some frequent Django and other libraries’ issues:

Issue:

from django.db.models.loading import get_models
ImportError: No module named loading

Solution:

from django.apps import apps

Issue:

from django.utils.importlib import import_module
ImportError: No module named importlib

Solution:

from importlib import import_module

Issue:

class ProductAdmin(reversion.VersionAdmin):
AttributeError: 'module' object has no attribute 'VersionAdmin'

Solution:

from reversion.admin import VersionAdmin

Issue:

@reversion.register
NameError: name 'reversion' is not defined

Solution:

from reversion import revisions

Issue:

django.utils.log.NullHandler class not found

Solution:

Use logging.NullHandler

This is pretty much it. Django upgrade is more of a task which needs a lot of patience than other things. Happy upgrading.

Django Update 1.6 to 1.9 – 1.6 to 1.8 and DRF Upgrade

This is going to be a series of posts describing briefly about something which turned my life upside down for few weeks. I am still in the process, as of now. Django upgrade teaches you a lot of things and when you are updating from a very old version to relatively newer one, it kills you, literally. You are up for an extremely bumpy ride that you will remember for a very very long time.

The first and the most difficult part is to upgrade the Django Rest Framework. I did not think this one was going to be such a biggie. We were on DRF 2.3.13 and without thinking a lot I took it to 3.4.0 and that was the first mistake that I did. All the test cases failed miserably and I started fixing them one by one. Some of them seemed self-explanatory and there were some issues which even Google failed to help. I struggled with these errors and they wasted 2 days. When nothing moved, I decided to move it to 3.0.5 first and then taking it to the other versions.

LESSON LEARNT – When upgrading a library, take it to just one major version above it and we must read the changelog carefully.

Upgrading to DRF 3.0.5 was relatively easier. There were some serializer issues which were mostly straightforward. And there were few deprecations as well. Then I took it to 3.1.1 which did not throw any extra error. Then upgraded to 3.2.1 and then to 3.3.1 and finally to 3.4.5. Meanwhile, I had upgraded Django to 1.8 which I shall discuss in the next post.

Some of the errors which frequently showed up are as below.

NotImplementedError: `request.QUERY_PARAMS` has been deprecated in favor of `request.query_params` since version 3.0, 
and has been fully removed as of version 3.2.

For the above one change QUERY_PARAMS to query_params. Simple googling can help here.

NotImplementedError: Field.to_representation() must be implemented for field id. 
If you do not need to support write operations you probably want to subclass `ReadOnlyField` instead.

This is one of the basic changes that you have to do. This one is basically asking you to change to:

order_id = serializers.Field(source='pk') # older
order_id = serializers.ReadOnlyField(source='pk') # newer
AssertionError: It is redundant to specify `source='discount_amount'` on field 'Field' in serializer 'OrderListSerializer', 
because it is the same as the field name. Remove the `source` keyword argument.

This error comes when in any of the fields of the serializer, you have the field name same as the source name.

discount_amount = serializers.ReadOnlyField(source='discount_amount') # older
discounted_amount = serializers.ReadOnlyField(source='discount_amount') # newer

Also, please take those serializers very seriously which take a list to serialize. The parameter many=True solves so many issues around them.

Some of the other issue which appeared, and I am sorry to have forgotten how they were fixed, are as below. I am sure, if you are this far, you will find them very easy to fix.

AttributeError: Got AttributeError when attempting to get a value for field `product` on serializer `ProductListSerializer`.
The serializer field might be named incorrectly and not match any attribute or key on the `RelatedManager` instance. 
Original exception text was: 'RelatedManager' object has no attribute 'product'
AttributeError: 'RelatedManager' object has no attribute
AttributeError: 'QuerySet' object has no attribute 'user'

Other changes include:

  • The earlier implementation where you had to define one custom to_native method has been changed to to_representation
class FinalRecordField(serializers.WritableField):

    def to_native(self, value):
        return value

to

class FinalStockRecordField(serializers.Serializer):

    def to_representation(self, instance):
        return instance
  • The library djangorestframework-xml had to be included as the default XML renderer was not working. I used version 1.3.0.

This is what I mostly remember. Try to be patient with the update as it has to be a disturbing thing. I am happily on DRF version 3.4.5. Next article will be on Django upgrade from 1.6 to 1.8.