Add more examples on how to initialize database with postgresql fixtu…

…re - refs #316

README.rst

@@ -105,6 +105,31 @@ If you want the database fixture to be automatically populated with your schema:
 
     The database will still be dropped each time.
 
+If you've got other programmatic ways to populate the database, you would need an additional fixture, that will take care of that:
+
+.. code-block:: python
+
+    @pytest.fixture(scope='function')
+    def db_session(postgresql):
+        """Session for SQLAlchemy."""
+        from pyramid_fullauth.models import Base  # pylint:disable=import-outside-toplevel
+
+        # NOTE: this fstring assumes that psycopg2 >= 2.8 is used. Not sure about it's support in psycopg2cffi (PyPy)
+        connection = f'postgresql+psycopg2://{postgres.info.user}:@{postgres.info.host}:{postgres.info.port}/{postgres.info.dbname}'
+
+        engine = create_engine(connection, echo=False, poolclass=NullPool)
+        pyramid_basemodel.Session = scoped_session(sessionmaker(extension=ZopeTransactionExtension()))
+        pyramid_basemodel.bind_engine(
+            engine, pyramid_basemodel.Session, should_create=True, should_drop=True)
+
+        yield pyramid_basemodel.Session
+
+        transaction.commit()
+        Base.metadata.drop_all(engine)
+
+See the original code at `pyramid_fullauth <https://github.com/fizyk/pyramid_fullauth/blob/2950e7f4a397b313aaf306d6d1a763ab7d8abf2b/tests/conftest.py#L35>`_.
+Depending on your needs, that in between code can fire alembic migrations in case of sqlalchemy stack or any other code
+
 
 
 Connecting to already existing postgresql database

src/pytest_postgresql/compat.py

@@ -0,0 +1,19 @@
+from typing import Any
+from platform import python_implementation
+
+try:
+    import psycopg2
+except ImportError:
+    psycopg2 = False
+
+if not psycopg2:
+    # if there's no postgres, just go with the flow.
+    # pylint:disable=invalid-name
+    cursor = Any
+    connection = Any
+elif python_implementation() == "PyPy":
+    from psycopg2cffi._impl.cursor import Cursor as cursor
+    from psycopg2cffi._impl.connection import Connection as connection
+else:
+    from psycopg2._psycopg import cursor
+    from psycopg2._psycopg import connection

src/pytest_postgresql/factories.py

@@ -25,8 +25,9 @@
 
 import pytest
 
+from pytest_postgresql.compat import psycopg2, connection
 from pytest_postgresql.executor_noop import NoopExecutor
-from pytest_postgresql.janitor import DatabaseJanitor, psycopg2
+from pytest_postgresql.janitor import DatabaseJanitor
 from pytest_postgresql.executor import PostgreSQLExecutor
 from pytest_postgresql.port import get_port
 
@@ -242,7 +243,7 @@ def postgresql_factory(request):
                 pg_user, pg_host, pg_port, pg_db, proc_fixture.version,
                 pg_password
         ):
-            connection = psycopg2.connect(
+            db_connection: connection = psycopg2.connect(
                 dbname=pg_db,
                 user=pg_user,
                 password=pg_password,
@@ -253,10 +254,11 @@ def postgresql_factory(request):
             if pg_load:
                 for filename in pg_load:
                     with open(filename, 'r') as _fd:
-                        with connection.cursor() as cur:
+                        with db_connection.cursor() as cur:
                             cur.execute(_fd.read())
-            yield connection
-            connection.close()
+            yield db_connection
+            db_connection.close()
+            db_connection.info
 
     return postgresql_factory
 

src/pytest_postgresql/janitor.py

@@ -1,21 +1,14 @@
 """Database Janitor."""
 from contextlib import contextmanager
 from types import TracebackType
-from typing import TypeVar, Union, Optional, Type, Any
+from typing import TypeVar, Union, Optional, Type
 
 from pkg_resources import parse_version
+
+from pytest_postgresql.compat import psycopg2, cursor
+
 Version = type(parse_version('1'))  # pylint:disable=invalid-name
 
-try:
-    import psycopg2
-    try:
-        from psycopg2._psycopg import cursor
-    except ImportError:
-        from psycopg2cffi._impl.cursor import Cursor as cursor
-except ImportError:
-    psycopg2 = False
-    # if there's no postgres, just go with the flow.
-    cursor = Any  # pylint:disable=invalid-name
 
 DatabaseJanitorType = TypeVar("DatabaseJanitorType", bound="DatabaseJanitor")