Merge pull request #10666 from scls19fr/issue_10654

read_sql/to_sql can accept database URI as con parameter

Author: jorisvandenbossche

doc/source/whatsnew/v0.17.0.txt

@@ -60,6 +60,8 @@ Releasing of the GIL could benefit an application that uses threads for user int
 Other enhancements
 ^^^^^^^^^^^^^^^^^^
 
+- `read_sql` and `to_sql` can accept database URI as con parameter (:issue:`10214`)
+
 - Enable `read_hdf` to be used without specifying a key when the HDF file contains a single dataset (:issue:`10443`)
 
 - ``DatetimeIndex`` can be instantiated using strings contains ``NaT`` (:issue:`7599`)

pandas/io/sql.py

@@ -289,7 +289,7 @@ def read_sql_table(table_name, con, schema=None, index_col=None,
     ----------
     table_name : string
         Name of SQL table in database
-    con : SQLAlchemy connectable
+    con : SQLAlchemy connectable (or database string URI)
         Sqlite DBAPI connection mode not supported
     schema : string, default None
         Name of SQL schema in database to query (if database flavor
@@ -328,6 +328,8 @@ def read_sql_table(table_name, con, schema=None, index_col=None,
     read_sql
 
     """
+    
+    con = _engine_builder(con)
     if not _is_sqlalchemy_connectable(con):
         raise NotImplementedError("read_sql_table only supported for "
                                   "SQLAlchemy connectable.")
@@ -362,7 +364,8 @@ def read_sql_query(sql, con, index_col=None, coerce_float=True, params=None,
     ----------
     sql : string
         SQL query to be executed
-    con : SQLAlchemy connectable(engine/connection) or sqlite3 DBAPI2 connection
+    con : SQLAlchemy connectable(engine/connection) or database string URI 
+        or sqlite3 DBAPI2 connection
         Using SQLAlchemy makes it possible to use any DB supported by that
         library.
         If a DBAPI2 object, only sqlite3 is supported.
@@ -420,7 +423,8 @@ def read_sql(sql, con, index_col=None, coerce_float=True, params=None,
     ----------
     sql : string
         SQL query to be executed or database table name.
-    con : SQLAlchemy connectable(engine/connection) or DBAPI2 connection (fallback mode)
+    con : SQLAlchemy connectable(engine/connection) or database string URI
+        or DBAPI2 connection (fallback mode)
         Using SQLAlchemy makes it possible to use any DB supported by that
         library.
         If a DBAPI2 object, only sqlite3 is supported.
@@ -504,7 +508,8 @@ def to_sql(frame, name, con, flavor='sqlite', schema=None, if_exists='fail',
     frame : DataFrame
     name : string
         Name of SQL table
-    con : SQLAlchemy connectable(engine/connection) or sqlite3 DBAPI2 connection
+    con : SQLAlchemy connectable(engine/connection) or database string URI
+        or sqlite3 DBAPI2 connection
         Using SQLAlchemy makes it possible to use any DB supported by that
         library.
         If a DBAPI2 object, only sqlite3 is supported.
@@ -584,6 +589,22 @@ def has_table(table_name, con, flavor='sqlite', schema=None):
                   "MySQL will be further supported with SQLAlchemy connectables.")
 
 
+def _engine_builder(con):
+    """
+    Returns a SQLAlchemy engine from a URI (if con is a string)
+    else it just return con without modifying it
+    """
+    if isinstance(con, string_types):
+        try:
+            import sqlalchemy
+            con = sqlalchemy.create_engine(con)
+            return con
+
+        except ImportError:
+            _SQLALCHEMY_INSTALLED = False
+
+    return con
+
 def pandasSQL_builder(con, flavor=None, schema=None, meta=None,
                       is_cursor=False):
     """
@@ -592,6 +613,7 @@ def pandasSQL_builder(con, flavor=None, schema=None, meta=None,
     """
     # When support for DBAPI connections is removed,
     # is_cursor should not be necessary.
+    con = _engine_builder(con)
     if _is_sqlalchemy_connectable(con):
         return SQLDatabase(con, schema=schema, meta=meta)
     else:

pandas/io/tests/test_sql.py

@@ -918,6 +918,23 @@ def test_sqlalchemy_type_mapping(self):
         table = sql.SQLTable("test_type", db, frame=df)
         self.assertTrue(isinstance(table.table.c['time'].type, sqltypes.DateTime))
 
+    def test_to_sql_read_sql_with_database_uri(self):
+
+        # Test read_sql and .to_sql method with a database URI (GH10654)
+        test_frame1 = self.test_frame1
+        #db_uri = 'sqlite:///:memory:' # raises sqlalchemy.exc.OperationalError: (sqlite3.OperationalError) near "iris": syntax error [SQL: 'iris']
+        with tm.ensure_clean() as name:
+            db_uri = 'sqlite:///' + name
+            table = 'iris'
+            test_frame1.to_sql(table, db_uri, if_exists='replace', index=False)
+            test_frame2 = sql.read_sql(table, db_uri)
+            test_frame3 = sql.read_sql_table(table, db_uri)
+            query = 'SELECT * FROM iris'
+            test_frame4 = sql.read_sql_query(query, db_uri)
+        tm.assert_frame_equal(test_frame1, test_frame2)
+        tm.assert_frame_equal(test_frame1, test_frame3)
+        tm.assert_frame_equal(test_frame1, test_frame4)
+
 
 class _EngineToConnMixin(object):
     """