when start python manage.py shell gives following error

deepak@deepak-Inspiron-1545:~/django/mysite$ python manage.py shell
Traceback (most recent call last):
File "manage.py", line 14, in <module>
execute_manager(settings)
File "/usr/local/lib/python2.7/dist-packages/django/core/management/__init__.py", line 438, in execute_manager
utility.execute()
File "/usr/local/lib/python2.7/dist-packages/django/core/management/__init__.py", line 379, in execute
self.fetch_command(subcommand).run_from_argv(self.argv)
File "/usr/local/lib/python2.7/dist-packages/django/core/management/base.py", line 191, in run_from_argv
self.execute(*args, **options.__dict__)
File "/usr/local/lib/python2.7/dist-packages/django/core/management/base.py", line 220, in execute
output = self.handle(*args, **options)
File "/usr/local/lib/python2.7/dist-packages/django/core/management/base.py", line 351, in handle
return self.handle_noargs(**options)
File "/usr/local/lib/python2.7/dist-packages/django/core/management/commands/shell.py", line 46, in handle_noargs
from django.db.models.loading import get_models
File "/usr/local/lib/python2.7/dist-packages/django/db/__init__.py", line 78, in <module>
connection = connectionsDEFAULT DB ALIAS
File "/usr/local/lib/python2.7/dist-packages/django/db/utils.py", line 93, in __getitem__
backend = load_backend(db['ENGINE'])
File "/usr/local/lib/python2.7/dist-packages/django/db/utils.py", line 33, in load_backend
return import_module('.base', backend_name)
File "/usr/local/lib/python2.7/dist-packages/django/utils/importlib.py", line 35, in import_module
__import__(name)
File "/usr/local/lib/python2.7/dist-packages/django/db/backends/postgresql_psycopg2/base.py", line 24, in <module>
raise ImproperlyConfigured("Error loading psycopg2 module: %s" % e)
django.core.exceptions.ImproperlyConfigured: Error loading psycopg2 module: No module named psycopg2