Connecting to an Oracle database using SQLAlchemy

You don't need to import cx_Oracle anymore. The newer version of the sqlalchemy module calls the function cx_Oracle.makedsn(). Have a look:

from sqlalchemy.engine import create_engine

DIALECT = 'oracle'
SQL_DRIVER = 'cx_oracle'
USERNAME = 'your_username' #enter your username
PASSWORD = 'your_password' #enter your password
HOST = 'subdomain.domain.tld' #enter the oracle db host url
PORT = 1521 # enter the oracle port number
SERVICE = 'your_oracle_service_name' # enter the oracle db service name
ENGINE_PATH_WIN_AUTH = DIALECT + '+' + SQL_DRIVER + '://' + USERNAME + ':' + PASSWORD +'@' + HOST + ':' + str(PORT) + '/?service_name=' + SERVICE

engine = create_engine(ENGINE_PATH_WIN_AUTH)


#test query
import pandas as pd
test_df = pd.read_sql_query('SELECT * FROM global_name', engine)

from sqlalchemy import create_engine
import cx_Oracle

host=hostname
port=port
sid='sid'
user='username'
password='password'
sid = cx_Oracle.makedsn(host, port, sid=sid)

cstr = 'oracle://{user}:{password}@{sid}'.format(
    user=user,
    password=password,
    sid=sid
)

engine =  create_engine(
    cstr,
    convert_unicode=False,
    pool_recycle=10,
    pool_size=50,
    echo=True
)

result = engine.execute('select * from TABLE')

for row in result:
    print row

This worked for me. A connection object can also be created like

conn = engine.connect()
conn.close()

which will enable to close the connection. This works even if you have a tunnel to your remote DB from your local port.

Assuming you have the Oracle client on your machine with a valid tnsnames.ora file, this works for me:

from sqlalchemy import create_engine
import pandas as pd 
engine = create_engine('oracle://myusername:mypassword@SID')
con = engine.connect()
outpt = con.execute("SELECT * FROM YOUR_TABLE")
df = pd.DataFrame(outpt.fetchall())
df.columns = outpt.keys()
print(df.head())
con.close() 

"... if you already have a connection string that works with cx_Oracle":

import pandas as pd
from sqlalchemy import create_engine
import cx_Oracle

conn_factory = lambda: conn_factory = lambda: cx_Oracle.connect(user=dbuser, password=dbpass, dsn=dsn)

engine = create_engine(
    "oracle://", 
    creator=conn_factory
)

data = pd.read_sql("SELECT 1 FROM DUAL", engine)

https://gist.github.com/DGrady/7fb5c2214f247dcff2cb5dd99e231483?permalink_comment_id=4035380#gistcomment-4035380

This works for me, when there is no tnsnames.ora file.

user = 'system'
pwd = 'oracle'
dsn = cx_Oracle.makedsn(
    '192.168.1.105', 49161,
    # service_name='your_service_name_if_any'
)
ora_engine = create_engine(f'oracle+cx_oracle://{user}:{pwd}@{dsn}', echo=True)
ora_engine.connect()

Using oracledb I first generate the DSN via the ConnectParams method. then I use that as the host with SQLAlchemy

import oracledb
import pandas as pd
from pandas import DataFrame
from sqlalchemy import create_engine, text
from sqlalchemy.engine import URL


def __get_dataframe(sql: str) -> DataFrame:
    cp = oracledb.ConnectParams(
        host="Server",
        port=1521,
        service_name="SID")

    connection_url = URL.create(
        "oracle+oracledb",
        host=cp.get_connect_string(),
        username="username",
        password="password",
    )
    with create_engine(connection_url).connect() as connection:
        data_frame = connection.execute(text(sql)).fetchall()

    return pd.DataFrame(data_frame)


results = __get_dataframe("SELECT 1 FROM DUAL")

Here's a slighty polished version of @mkarun2's answer.

Prerequisites:

• Install packages:

  sudo apt install libaio1

• Download Oracle InstantClient library

• Make a symlink:

  ln -s libclntsh.so.21.1 libclntsh.so

• Run the app like this:

  export LD_LIBRARY_PATH=oracle-instantclient/instantclient_21_1 python main.py

Heres main.py:

import cx_Oracle
import sqlalchemy as sa


# Use your config
username = 'username'
password = 'security'
hostname = 'localhost'
service_name = 'Xal' or None
port = '1521'


# Tell cx_Oracle where to find the libraries. Optional.
cx_Oracle.init_oracle_client(lib_dir='oracle-instantclient/instantclient_21_1')


# Connection string
oracle_connection_string_fmt = (
    'oracle+cx_oracle://{username}:{password}@' +
    cx_Oracle.makedsn('{hostname}', '{port}', service_name='{service_name}')
)
url = oracle_connection_string_fmt.format(
    username=username, password=password, 
    hostname=hostname, port=port, 
    service_name=service_name,
)

# Create SqlAlchemy Engine
engine: sa.engine.Engine = sa.create_engine(url, echo=True)

Here's how to make your first query:

res: sa.engine.cursor.LegacyCursorResult = engine.execute("SELECT * FROM tablename")
for row in res:
    print(row)

notice that the query does not have ; at the end ;) Oracle does not like semicolons.