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INTRODUCTION TOSQLALCHEMY ORM
Created by / Jason A Myers @jasonamyers
WARNING!
SQLALCHEMY
Core - Schema centric
ORM - User Model
INSTALLINGpip install sqlalchemy
CONNECTING AND ESTABLISHING ASESSION
CONNECTING
from sqlalchemy import create_engine
engine = create_engine('sqlite:///:memory:')
ESTABLISHING A SESSIONfrom sqlalchemy.orm import sessionmaker
Session = sessionmaker(bind=engine)
session = Session()
DEFINING MODELS
MODEL BASE
Declarative Base
from sqlalchemy.ext.declarative import declarative_base
Base = declarative_base()
COOKIE MODEL
from sqlalchemy import Column, Integer, Numeric, String
class Cookie(Base): __tablename__ = 'cookies'
cookie_id = Column(Integer, primary_key=True) cookie_name = Column(String(50), index=True) cookie_recipe_url = Column(String(255)) cookie_sku = Column(String(55)) quantity = Column(Integer()) unit_cost = Column(Numeric(12, 2))
PERSISTING OUR TABLE
Base.metadata.create_all(engine)
INSERTING DATA
ADDING A COOKIE
cc_cookie = Cookie(cookie_name='chocolate chip', cookie_recipe_url='http://some.aweso.me/cookie/recipe.html', cookie_sku='CC01', quantity=12, unit_cost=0.50)
ADDING TO SESSION
session.add(cc_cookie)session.commit()
ACCESSING ATTRIBUTESprint(cc_cookie.cookie_id)
1
BULK INSERTSc1 = Cookie(cookie_name='peanut butter', cookie_recipe_url='http://some.aweso.me/cookie/peanut.html', cookie_sku='PB01', quantity=24, unit_cost=0.25)c2 = Cookie(cookie_name='oatmeal raisin', cookie_recipe_url='http://some.okay.me/cookie/raisin.html', cookie_sku='EWW01', quantity=100, unit_cost=1.00)session.bulk_save_objects([c1,c2])session.commit()
BULK INSERT DIFFERENCESc1.cookie_id
QUERIES
ALL THE COOKIES!cookies = session.query(Cookie).all()print(cookies)
[Cookie(cookie_name='chocolate chip', cookie_recipe_url='http://some.aweso.me/cookie/recipe.html', cookie_sku='CC01', quantity=12, unit_cost=0.50), Cookie(cookie_name='peanut butter', cookie_recipe_url='http://some.aweso.me/cookie/peanut.html', cookie_sku='PB01', quantity=24, unit_cost=0.25), Cookie(cookie_name='oatmeal raisin', cookie_recipe_url='http://some.okay.me/cookie/raisin.html', cookie_sku='EWW01', quantity=100, unit_cost=1.00)]
ALL THE COOKIES! - ITERATORfor cookie in session.query(Cookie): print(cookie)
Cookie(cookie_name='chocolate chip', cookie_recipe_url='http://some.aweso.me/cookie/recipe.html', cookie_sku='CC01', quantity=12, unit_cost=0.50)Cookie(cookie_name='peanut butter', cookie_recipe_url='http://some.aweso.me/cookie/peanut.html', cookie_sku='PB01', quantity=24, unit_cost=0.25)Cookie(cookie_name='oatmeal raisin', cookie_recipe_url='http://some.okay.me/cookie/raisin.html', cookie_sku='EWW01', quantity=100, unit_cost=1.00)
PARTICULAR ATTRIBUTESprint(session.query(Cookie.cookie_name, Cookie.quantity).first())
('chocolate chip', 12)
ORDER BY
for cookie in session.query(Cookie).order_by(Cookie.quantity): print('{:3} - {}'.format(cookie.quantity, cookie.cookie_name))
12 - chocolate chip 24 - peanut butter 100 - oatmeal raisin
DECENDINGfrom sqlalchemy import descfor cookie in session.query(Cookie).order_by(desc(Cookie.quantity)): print('{:3} - {}'.format(cookie.quantity, cookie.cookie_name))
LIMITINGquery = session.query(Cookie).order_by(Cookie.quantity).limit(2)print([result.cookie_name for result in query])
['chocolate chip', 'peanut butter']
DATABASE FUNCTIONS
from sqlalchemy import func
inv_count = session.query(func.sum(Cookie.quantity)).scalar()print(inv_count)
136
DATABASE FUNCTIONS COUNT
rec_count = session.query(func.count(Cookie.cookie_name)).first()print(rec_count)
(3, 0)
LABELINGrec_count = session.query(func.count(Cookie.cookie_name) \ .label('inventory_count')).first()print(rec_count.keys())print(rec_count.inventory_count)
['inventory_count']5
FILTER_BYrecord = session.query(Cookie). \ filter_by(cookie_name='chocolate chip').first()print(record)
Cookie(cookie_name='chocolate chip', cookie_recipe_url='http://some.aweso.me/cookie/recipe.html', cookie_sku='CC01', quantity=12, unit_cost=0.50)
FILTERrecord = session.query(Cookie). \ filter(Cookie.cookie_name == 'chocolate chip').first()print(record)
CLAUSEELEMENTSquery = session.query(Cookie).filter( Cookie.cookie_name.like('%chocolate%'))for record in query: print(record.cookie_name)
chocolate chip
CLAUSEELEMENT METHODS
between(cleft, cright) - Find where the column is between
cleft and cright
distinct() - Find only unique values for column
in_([list]) - Find where the column is in the list
is_(None) - Find where the column is None (commonly
used for Null checks with None)
contains('string') - Find where the column has 'string' in it
(Case-sensitive)
endswith('string') - Find where the column ends with
'string' (Case-sensitive)
startswith('string') - Find where the column begins with
'string' (Case-sensitive)
ilike('string') - Find where the column is like 'string' (NOT
Case-sensitive)
OPERATORS
from sqlalchemy import castquery = session.query(Cookie.cookie_name, cast((Cookie.quantity * Cookie.unit_cost), Numeric(12,2)).label('inv_cost'))for result in query: print('{} - {}'.format(result.cookie_name, result.inv_cost))
chocolate chip - 6.00peanut butter - 6.00oatmeal raisin - 100.00
CONJUNCTIONS
from sqlalchemy import and_, or_, not_query = session.query(Cookie).filter( or_( Cookie.quantity.between(10, 50), Cookie.cookie_name.contains('chip') ))for result in query: print(result.cookie_name)
chocolate chippeanut butter
UPDATING COOKIES
UPDATING COOKIES
query = session.query(Cookie)cc_cookie = query.filter(Cookie.cookie_name == "chocolate chip").first()
cc_cookie.quantity = cc_cookie.quantity + 120
session.commit()print(cc_cookie.quantity)
132
DELETING COOKIES
DELETING COOKIES
query = session.query(Cookie)query = query.filter(Cookie.cookie_name == "peanut butter")
dcc_cookie = query.one()session.delete(dcc_cookie)session.commit()
dcc_cookie = query.first()print(dcc_cookie)
None
OKAY TIME FOR A BREATHER
RELATIONSHIPS
IMPORTS
from datetime import datetimefrom sqlalchemy import DateTime, ForeignKey, Booleanfrom sqlalchemy.orm import relationship, backref
USER MODEL
class User(Base): __tablename__ = 'users'
user_id = Column(Integer(), primary_key=True) username = Column(String(15), nullable=False, unique=True) email_address = Column(String(255), nullable=False) phone = Column(String(20), nullable=False) password = Column(String(25), nullable=False) created_on = Column(DateTime(), default=datetime.now) updated_on = Column(DateTime(), default=datetime.now, onupdate=datetime.now)
ORDER MODEL
class Order(Base):
__tablename__ = 'orders'
order_id = Column(Integer(), primary_key=True)
user_id = Column(Integer(), ForeignKey('users.user_id'))
shipped = Column(Boolean(), default=False)
user = relationship("User", backref=backref('orders', order_by=order_id))
LINEITEM MODEL
class LineItem(Base):
__tablename__ = 'line_items'
line_item_id = Column(Integer(), primary_key=True)
order_id = Column(Integer(), ForeignKey('orders.order_id'))
cookie_id = Column(Integer(), ForeignKey('cookies.cookie_id'))
quantity = Column(Integer())
extended_cost = Column(Numeric(12, 2))
order = relationship("Order", backref=backref('line_items', order_by=line_item_id))
cookie = relationship("Cookie", uselist=False)
PERSIST THEM
Base.metadata.create_all(engine)
DEFINING A USERcookiemon = User(username='cookiemon', email_address='[email protected]', phone='111-111-1111', password='password')
session.add(cookiemon)
session.commit()
SETTING UP AN ORDER
o1 = Order()
o1.user = cookiemon
session.add(o1)
PREPARING LINE ITEMScc = session.query(Cookie).filter(Cookie.cookie_name == "chocolate chip").one()line1 = LineItem(cookie=cc, quantity=2, extended_cost=1.00)
pb = session.query(Cookie).filter(Cookie.cookie_name == "oatmeal raisin").one()line2 = LineItem(quantity=12, extended_cost=3.00)line2.cookie = pb
ASSOCIATE ORDER AND LINE ITEMS
o1.line_items.append(line1)o1.line_items.append(line2)
session.commit()
USING RELATIONSHIPS IN QUERIESquery = session.query(Order.order_id, User.username, User.phone,
Cookie.cookie_name, LineItem.quantity,
LineItem.extended_cost)
query = query.join(User).join(LineItem).join(Cookie)
results = query.filter(User.username == 'cookiemon').all()
print(results)
[(1, 'cookiemon', '111-111-1111', 'chocolate chip', 2, Decimal('1.00')),
(1, 'cookiemon', '111-111-1111', 'oatmeal raisin', 12, Decimal('3.00'
ANOTHER EXAMPLEquery = session.query(User.username, func.count(Order.order_id))
query = query.outerjoin(Order).group_by(User.username)
for row in query:
print(row)
('cookiemon', 1)
WHAT OTHER THINGS ARE OUTTHERE?
AutomapGeospatial Queries
QUESTIONS
Jason Myers / @jasonamyers / Essential SQLAlchemy
