Upgrade to Flask 0.10 Error in serializing models to JSON

Question

Here is the error I continue to get after upgrading my Flask app to version 0.10:

AttributeError: 'Flask' object has no attribute 'json_encoder'

I realize in the release note it mentions many upgrades to the JSON serialization but it doesn't say anything about it breaking current implementations. Does anyone know of a fix for this?

UPDATE:

Here's the full stacktrace --

    Traceback (most recent call last):
  File "/Users/un/sites/env/visual_mg/lib/python2.7/site-packages/flask/app.py", line 1701, in __call__
    return self.wsgi_app(environ, start_response)
  File "/Users/un/sites/env/visual_mg/lib/python2.7/site-packages/flask/app.py", line 1689, in wsgi_app
    response = self.make_response(self.handle_exception(e))
  File "/Users/un/sites/env/visual_mg/lib/python2.7/site-packages/flask/app.py", line 1687, in wsgi_app
    response = self.full_dispatch_request()
  File "/Users/un/sites/env/visual_mg/lib/python2.7/site-packages/flask/app.py", line 1360, in full_dispatch_request
    rv = self.handle_user_exception(e)
  File "/Users/un/sites/env/visual_mg/lib/python2.7/site-packages/flask/app.py", line 1358, in full_dispatch_request
    rv = self.dispatch_request()
  File "/Users/un/sites/env/visual_mg/lib/python2.7/site-packages/flask/app.py", line 1344, in dispatch_request
    return self.view_functions[rule.endpoint](**req.view_args)
  File "/Users/un/Sites/visual_mg/visual/attrs/views.py", line 165, in attrs_hs
    return get_attrs(Attr, Attr_id, Attr_weight_tbl, Attr_weight_col, Attr_weight_mergeid, Attr_id_lens)
  File "/Users/un/Sites/visual_mg/visual/attrs/views.py", line 129, in get_attrs
    return jsonify(ret)
  File "/Users/un/sites/env/visual_mg/lib/python2.7/site-packages/flask/helpers.py", line 198, in jsonify
    indent=None if request.is_xhr else 2), mimetype='application/json')
  File "/Users/un/sites/env/visual_mg/lib/python2.7/site-packages/flask/json.py", line 124, in dumps
    _dump_arg_defaults(kwargs)
  File "/Users/un/sites/env/visual_mg/lib/python2.7/site-packages/flask/json.py", line 97, in _dump_arg_defaults
    kwargs.setdefault('cls', current_app.json_encoder)
  File "/Users/un/sites/env/visual_mg/lib/python2.7/site-packages/werkzeug/local.py", line 336, in __getattr__
    return getattr(self._get_current_object(), name)
AttributeError: 'Flask' object has no attribute 'json_encoder'

UPDATE #2:

Here's a copy of all python libs --

Babel==0.9.6
Flask==0.10.1
Flask-Babel==0.8
Flask-Login==0.1.3
Flask-OAuth==0.12
Flask-SQLAlchemy==0.16
Flask-Script==0.5.3
Flask-WTF==0.8.3
Flask-WhooshAlchemy==0.55a
Jinja2==2.7
MarkupSafe==0.18
MySQL-python==1.2.3
SQLAlchemy==0.8.1
WTForms==1.0.4
Werkzeug==0.9.1
Whoosh==2.4.1
blinker==1.2
distribute==0.6.26
hiredis==0.1.1
httplib2==0.8
ipython==0.13.2
itsdangerous==0.21
matplotlib==1.2.1
numpy==1.7.1
oauth2==1.5.211
pandas==0.11.0
patsy==0.1.0
python-dateutil==2.1
pytz==2013b
readline==6.2.4.1
redis==2.7.6
scikits.statsmodels==0.3.1
scipy==0.12.0
six==1.3.0
speaklater==1.3
virtualenv==1.7.2
virtualenv-clone==0.2.4
virtualenvwrapper==3.5
wsgiref==0.1.2

Answer 1

This was the fix for me:

sudo apt-get install python-simplejson