Django 1.8 psycopg2 import error

Question

I have psycopg2 installed on my computer under C:\Python34\Lib\site-packages\psycopg2 If I use a postgresql database in a django project outside a virtual environment, I get no error.But, when I want to transfer the project to a virtual env so that I can deploy it on heroku. But when I try to migrate the database I get an error saying psycopg2 module is not present. I even tried to install it inside the virtual env using pip install psycopg2 and even that didn't work. Here is the full traceback.

(denv) C:\Users\Saket\denv\musicalguru>python manage.py migrate
  Traceback (most recent call last):
  File "C:\Users\Saket\denv\lib\site- packages\django\db\backends\postgresql_psycopg2\base.py", line 20, in <module>
  import psycopg2 as Database
  File "C:\Users\Saket\denv\lib\site-packages\psycopg2\__init__.py", line 50, in<module>from psycopg2._psycopg import BINARY, NUMBER, STRING, DATETIME, ROWID
  ImportError: DLL load failed: The specified module could not be found.

  During handling of the above exception, another exception occurred:

  Traceback (most recent call last):
  File "manage.py", line 10, in <module>
  execute_from_command_line(sys.argv)
  File  "C:\Users\Saket\denv\lib\sitepackages
  \django\core\management\__init__.py", line 338, in execute_from_command_line
  utility.execute()
  File "C:\Users\Saket\denv\lib\site-   packages\django\core\management\__init__.py", line 312, in execute
  django.setup()
  File "C:\Users\Saket\denv\lib\site-packages\django\__init__.py", line 18, in setup
  apps.populate(settings.INSTALLED_APPS)
  File "C:\Users\Saket\denv\lib\site-packages\django\apps\registry.py", line 108, in populate
  app_config.import_models(all_models)
  File "C:\Users\Saket\denv\lib\site-packages\django\apps\config.py", line 198,in import_models
  self.models_module = import_module(models_module_name)
   File "C:\Users\Saket\denv\lib\importlib\__init__.py", line 109, in  import_module
   return _bootstrap._gcd_import(name[level:], package, level)
   File "<frozen importlib._bootstrap>", line 2254, in _gcd_import
   File "<frozen importlib._bootstrap>", line 2237, in _find_and_load
    File "<frozen importlib._bootstrap>", line 2226, in  _find_and_load_unlocked
    File "<frozen importlib._bootstrap>", line 1200, in _load_unlocked
    File "<frozen importlib._bootstrap>", line 1129, in _exec
    File "<frozen importlib._bootstrap>", line 1471, in exec_module
    File "<frozen importlib._bootstrap>", line 321, in  _call_with_frames_removed
   File "C:\Users\Saket\denv\lib\site- packages\django\contrib\auth\models.py", line 41, in <module>
   class Permission(models.Model):
   File "C:\Users\Saket\denv\lib\site-packages\django\db\models\base.py", line 139, in __new__
    new_class.add_to_class('_meta', Options(meta, **kwargs))
   File "C:\Users\Saket\denv\lib\site-packages\django\db\models\base.py", line 324, in add_to_class
   value.contribute_to_class(cls, name)
   File "C:\Users\Saket\denv\lib\site-packages\django\db\models\options.py", line 250, in contribute_to_class
   self.db_table = truncate_name(self.db_table,  connection.ops.max_name_length())
   File "C:\Users\Saket\denv\lib\site-packages\django\db\__init__.py", line 36, in __getattr__
   return getattr(connections[DEFAULT_DB_ALIAS], item)
   File "C:\Users\Saket\denv\lib\site-packages\django\db\utils.py", line 240, in__getitem__
   backend = load_backend(db['ENGINE'])
   File "C:\Users\Saket\denv\lib\site-packages\django\db\utils.py", line 111, in
   load_backend
   return import_module('%s.base' % backend_name)
   File "C:\Users\Saket\denv\lib\importlib\__init__.py", line 109, in   import_module
   return _bootstrap._gcd_import(name[level:], package, level)
    File "<frozen importlib._bootstrap>", line 2254, in _gcd_import
     File "<frozen importlib._bootstrap>", line 2237, in _find_and_load
     File "<frozen importlib._bootstrap>", line 2226, in  _find_and_load_unlocked
    File "<frozen importlib._bootstrap>", line 1200, in _load_unlocked
    File "<frozen importlib._bootstrap>", line 1129, in _exec
    File "<frozen importlib._bootstrap>", line 1471, in exec_module
    File "<frozen importlib._bootstrap>", line 321, in  _call_with_frames_removed
    File   "C:\Users\Saket\denv\lib\sitepackages\django\db\backends\postgresql_psyc
    opg2\base.py", line 24, in <module>
    raise ImproperlyConfigured("Error loading psycopg2 module: %s" % e)
    django.core.exceptions.ImproperlyConfigured: Error loading psycopg2  module: DLL
    load failed: The specified module could not be found.

Answer 1

I used the instructions to install in virtual env from here

And then added PostgreSQL's 'bin' directory on the system path. That seemed to do the trick.

Answer 2

Intalling psycopg2 from source into virtualenv under windows is a pain.

Instead you can create the virtualenv that have access to system wide installed packages.

virtualenv --system-site-packages env_dir