sqlalchemy.engine create_engine Example Code

create_engine is a callable within the sqlalchemy.engine module of the SQLAlchemy project.

Connection, Engine, default, and url are several other callables with code examples from the same sqlalchemy.engine package.

Example 1 from PyHive

PyHive (PyPI package information) is a set of DB-API and SQLAlchemy interfaces that make it easier to use Presto and Apache Hive with Python. Dropbox's engineering team created this code library, open sourced it and put it out under the Apache 2.0 license.

PyHive / pyhive / tests / test_sqlalchemy_hive.py

# test_sqlalchemy_hive.py
from __future__ import absolute_import
from __future__ import unicode_literals
from builtins import str
from pyhive.sqlalchemy_hive import HiveDate
from pyhive.sqlalchemy_hive import HiveDecimal
from pyhive.sqlalchemy_hive import HiveTimestamp
from pyhive.tests.sqlalchemy_test_case import SqlAlchemyTestCase
from pyhive.tests.sqlalchemy_test_case import with_engine_connection
from sqlalchemy import types
from sqlalchemy.engine import create_engine
from sqlalchemy.schema import Column
from sqlalchemy.schema import MetaData
from sqlalchemy.schema import Table
import contextlib
import datetime
import decimal
import sqlalchemy.types
import unittest

_ONE_ROW_COMPLEX_CONTENTS = [
    True,
    127,
    32767,
    2147483647,
    9223372036854775807,
    0.5,
    0.25,
    'a string',
    datetime.datetime(1970, 1, 1),
    b'123',
    '[1,2]',
    '{1:2,3:4}',
    '{"a":1,"b":2}',
    '{0:1}',
    decimal.Decimal('0.1'),
]




class TestSqlAlchemyHive(unittest.TestCase, SqlAlchemyTestCase):
    def create_engine(self):
        return create_engine('hive://localhost:10000/default')

    @with_engine_connection
    def test_dotted_column_names(self, engine, connection):
        row = connection.execute('SELECT * FROM one_row').fetchone()
        assert row.keys() == ['number_of_rows']
        assert 'number_of_rows' in row
        assert row.number_of_rows == 1
        assert row['number_of_rows'] == 1
        assert getattr(row, 'one_row.number_of_rows') == 1
        assert row['one_row.number_of_rows'] == 1

    @with_engine_connection
    def test_dotted_column_names_raw(self, engine, connection):
        row = connection.execution_options(hive_raw_colnames=True) \
            .execute('SELECT * FROM one_row').fetchone()
        assert row.keys() == ['one_row.number_of_rows']
        assert 'number_of_rows' not in row
        assert getattr(row, 'one_row.number_of_rows') == 1
        assert row['one_row.number_of_rows'] == 1

    @with_engine_connection
    def test_reflect_select(self, engine, connection):
        one_row_complex = Table('one_row_complex', MetaData(bind=engine), autoload=True)
        self.assertEqual(len(one_row_complex.c), 15)


## ... source file abbreviated to get to create_engine examples ...


        self.assertIsInstance(one_row_complex.c.double.type, types.Float)
        self.assertIsInstance(one_row_complex.c.string.type, types.String)
        self.assertIsInstance(one_row_complex.c.timestamp.type, HiveTimestamp)
        self.assertIsInstance(one_row_complex.c.binary.type, types.String)
        self.assertIsInstance(one_row_complex.c.array.type, types.String)
        self.assertIsInstance(one_row_complex.c.map.type, types.String)
        self.assertIsInstance(one_row_complex.c.struct.type, types.String)
        self.assertIsInstance(one_row_complex.c.union.type, types.String)
        self.assertIsInstance(one_row_complex.c.decimal.type, HiveDecimal)

    @with_engine_connection
    def test_type_map(self, engine, connection):
        row = connection.execute('SELECT * FROM one_row_complex').fetchone()
        self.assertListEqual(list(row), _ONE_ROW_COMPLEX_CONTENTS)

    @with_engine_connection
    def test_reserved_words(self, engine, connection):
        fake_table = Table('select', MetaData(bind=engine), Column('map', sqlalchemy.types.String))
        query = str(fake_table.select(fake_table.c.map == 'a'))
        self.assertIn('`select`', query)
        self.assertIn('`map`', query)
        self.assertNotIn('"select"', query)
        self.assertNotIn('"map"', query)

    def test_switch_database(self):
        engine = create_engine('hive://localhost:10000/pyhive_test_database')
        try:
            with contextlib.closing(engine.connect()) as connection:
                self.assertIn(
                    ('dummy_table',),
                    connection.execute('SHOW TABLES').fetchall()
                )
                connection.execute('USE default')
                self.assertIn(
                    ('one_row',),
                    connection.execute('SHOW TABLES').fetchall()
                )
        finally:
            engine.dispose()

    @with_engine_connection
    def test_lots_of_types(self, engine, connection):
        types = [
            'INT', 'CHAR', 'VARCHAR', 'NCHAR', 'TEXT', 'Text', 'FLOAT',
            'NUMERIC', 'DECIMAL', 'TIMESTAMP', 'DATETIME', 'CLOB', 'BLOB',
            'BOOLEAN', 'SMALLINT', 'DATE', 'TIME',
            'String', 'Integer', 'SmallInteger',
            'Numeric', 'Float', 'DateTime', 'Date', 'Time', 'LargeBinary',
            'Boolean', 'Unicode', 'UnicodeText',
        ]


## ... source file continues with no further create_engine examples...

Example 2 from sqlacodegen

sqlacodegen (PyPI package information) is a tool for reading from an existing relational database to generate code to create SQLAlchemy models based on that database. The project is primarily written and maintained by Alex Grönholm (agronholm) and it is open sourced under the MIT license.

sqlacodegen / sqlacodegen / main.py

# main.py
from __future__ import unicode_literals, division, print_function, absolute_import

import argparse
import io
import sys

import pkg_resources
from sqlalchemy.engine import create_engine
from sqlalchemy.schema import MetaData

from sqlacodegen.codegen import CodeGenerator


def main():
    parser = argparse.ArgumentParser(
        description='Generates SQLAlchemy model code from an existing database.')
    parser.add_argument('url', nargs='?', help='SQLAlchemy url to the database')
    parser.add_argument('--version', action='store_true', help="print the version number and exit")
    parser.add_argument('--schema', help='load tables from an alternate schema')
    parser.add_argument('--tables', help='tables to process (comma-separated, default: all)')
    parser.add_argument('--noviews', action='store_true', help="ignore views")
    parser.add_argument('--noindexes', action='store_true', help='ignore indexes')
    parser.add_argument('--noconstraints', action='store_true', help='ignore constraints')
    parser.add_argument('--nojoined', action='store_true',
                        help="don't autodetect joined table inheritance")
    parser.add_argument('--noinflect', action='store_true',
                        help="don't try to convert tables names to singular form")
    parser.add_argument('--noclasses', action='store_true',
                        help="don't generate classes, only tables")
    parser.add_argument('--nocomments', action='store_true', help="don't render column comments")
    parser.add_argument('--outfile', help='file to write output to (default: stdout)')
    args = parser.parse_args()

    if args.version:
        version = pkg_resources.get_distribution('sqlacodegen').parsed_version
        print(version.public)
        return
    if not args.url:
        print('You must supply a url\n', file=sys.stderr)
        parser.print_help()
        return

    engine = create_engine(args.url)
    metadata = MetaData(engine)
    tables = args.tables.split(',') if args.tables else None
    metadata.reflect(engine, args.schema, not args.noviews, tables)

    outfile = io.open(args.outfile, 'w', encoding='utf-8') if args.outfile else sys.stdout
    generator = CodeGenerator(metadata, args.noindexes, args.noconstraints, args.nojoined,
                              args.noinflect, args.noclasses, nocomments=args.nocomments)
    generator.render(outfile)



## ... source file continues with no further create_engine examples...

Example 3 from sqlalchemy-clickhouse

sqlalchemy-clickhouse is a SQLAlchemy Dialect for communicating with the open source ClickHouse database management system. ClickHouse is column-oriented and therefore better for some use cases and worse for others compared to a traditional relational database.

The code for this project is open sourced under the MIT license while ClickHouse is provided as open source under the Apache License 2.0.

sqlalchemy-clickhouse / example.py

# example.py

import connector
cursor = connector.connect('default').cursor()
cursor.execute('SELECT * FROM test LIMIT 10')
print(cursor.fetchone())

from sqlalchemy.dialects import registry
registry.register("clickhouse", "base", "dialect")

from sqlalchemy import *
from sqlalchemy.engine import create_engine
from sqlalchemy.schema import *

engine = create_engine('clickhouse://default:@localhost:8123/default')
logs = Table('test', MetaData(bind=engine), autoload=True)
print(select([func.count('*')], from_obj=logs).scalar())



## ... source file continues with no further create_engine examples...

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