Essential SQLAlchemy: Chapter 7 (P.II)
This commit is contained in:
Pavel Vavilin
@@ -3853,7 +3853,7 @@ Table(
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* Chapter 7: Working with Data via SQLAlchemy ORM
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** SQLAlchemy v1
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:PROPERTIES:
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:header-args:python: :session *ch7-v1* :tangle ch7-v1.py :cache no
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:header-args:python: :session *ch7-v1* :tangle ch7-v1.py :cache yes
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:END:
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#+BEGIN_SRC python :shebang "#!/usr/bin/env python3" :results none
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@@ -3991,5 +3991,298 @@ Table(
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)
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]
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#+end_example
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**** Controlling the Columns in the Query
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#+BEGIN_SRC python :results table
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session.query(Cookie.cookie_name, Cookie.quantity).first()
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#+END_SRC
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#+RESULTS:
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| chocolate chip | 12 |
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**** Ordering
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#+BEGIN_SRC python :results table
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results = [('quantity', 'cookie_name')]
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for cookie in session.query(Cookie).order_by(Cookie.quantity):
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results.append((cookie.quantity, cookie.cookie_name))
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results
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#+END_SRC
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#+RESULTS[f815708c1194af5a00412df8cece6ec9db3af9ad]:
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| quantity | cookie_name |
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| 1 | dark chocolate chip |
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| 1 | molasses |
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| 12 | chocolate chip |
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| 24 | peanut butter |
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| 100 | oatmeal raisin |
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#+BEGIN_SRC python :results value table
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import pandas as pd
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from sqlalchemy import desc
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results = {'quantity': [], 'cookie_name': []}
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for cookie in session.query(Cookie).order_by(desc(Cookie.quantity)):
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results['quantity'].append(cookie.quantity)
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results['cookie_name'].append(cookie.cookie_name)
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df = pd.DataFrame(results)
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# Преобразуем DataFrame в список списков для Org Babel
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# 1. Заголовки: берем названия колонок и добавляем пустую ячейку для индекса
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headers = [''] + df.columns.tolist()
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# 2. Данные: объединяем индекс и значения строк
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rows = [[idx] + row.tolist() for idx, row in df.iterrows()]
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# 3. Собираем всё вместе: заголовки + разделитель (None) + строки
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summary = [headers] + [None] + rows
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summary
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#+END_SRC
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#+RESULTS[be902b1b955e9eadcdc6ba6670ac21a903f3f662]:
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| | quantity | cookie_name |
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|---+----------+---------------------|
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| 0 | 100 | oatmeal raisin |
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| 1 | 24 | peanut butter |
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| 2 | 12 | chocolate chip |
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| 3 | 1 | dark chocolate chip |
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| 4 | 1 | molasses |
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**** Limiting
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#+BEGIN_SRC python :results table
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query = session.query(Cookie).order_by(Cookie.quantity)[:2]
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# query = session.query(Cookie).order_by(Cookie.quantity).limit(2)
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[(result.cookie_name,) for result in query]
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#+END_SRC
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#+RESULTS[8c45f7d97da1645225462855a200559d1feaec44]:
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| dark chocolate chip |
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| molasses |
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**** Functions and Labels
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#+BEGIN_SRC python :results value
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from sqlalchemy import func
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inv_count = session.query(func.sum(Cookie.quantity)).scalar()
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inv_count
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#+END_SRC
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#+RESULTS[f1b621d0ce17b8f55883a46a7777bbeb162e412c]:
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: 138
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#+BEGIN_SRC python :results raw
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rec_count = session.query(func.count(Cookie.cookie_name)).first()
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rec_count
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#+END_SRC
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#+RESULTS[10949d37140b7bcb96a26788a765d195b86950c7]:
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(5,)
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#+BEGIN_SRC python :results table
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rec_count = session.query(
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func.count(Cookie.cookie_name).label("inventory_count")
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).first()
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(list(rec_count._mapping.keys()), (rec_count.inventory_count, ))
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#+END_SRC
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#+RESULTS[bc76d2b5448873014373602ade270610b301b86a]:
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| inventory_count |
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| 5 |
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**** Filtering
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#+BEGIN_SRC python :results value
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record = session.query(Cookie).filter(Cookie.cookie_name == "chocolate chip").first()
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record
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#+END_SRC
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#+RESULTS[00fbaff9a1d4dcb32caf86614258e147478b1a39]:
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: Cookie(
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: cookie_id="1",
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: cookie_name="chocolate chip",
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: cookie_recipe_url="http://some.aweso.me/cookie/recipe.html",
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: cookie_sku="CC01",
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: quantity="12",
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: unit_cost="0.50",
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: )
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#+BEGIN_SRC python :results value
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record = session.query(Cookie).filter_by(cookie_name="chocolate chip").first()
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record
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#+END_SRC
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#+RESULTS[c00b3f6260c658d7a3e6fe76c8cb1fa00d9dd58a]:
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: Cookie(
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: cookie_id="1",
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: cookie_name="chocolate chip",
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: cookie_recipe_url="http://some.aweso.me/cookie/recipe.html",
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: cookie_sku="CC01",
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: quantity="12",
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: unit_cost="0.50",
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: )
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#+BEGIN_SRC python :results table
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query = session.query(Cookie).filter(Cookie.cookie_name.like("chocolate chip"))
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[record.cookie_name for record in query]
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#+END_SRC
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#+RESULTS[498d5d0b02d3bea28799083caf1de588eccebac1]:
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| chocolate chip |
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**** Operators
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#+BEGIN_SRC python :results table
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results = session.query(Cookie.cookie_name, "SKU-" + Cookie.cookie_sku).all()
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[row for row in results]
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#+END_SRC
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#+RESULTS[18ddc67a0b92126197fac22eea073f2e86cf5388]:
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| chocolate chip | SKU-CC01 |
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| dark chocolate chip | SKU-CC02 |
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| molasses | SKU-MOL01 |
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| peanut butter | SKU-PB01 |
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| oatmeal raisin | SKU-EWW01 |
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#+BEGIN_SRC python :results table
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from sqlalchemy import cast
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query = session.query(
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Cookie.cookie_name,
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cast((Cookie.quantity * Cookie.unit_cost), Numeric(12, 2)).label("inv_cost"),
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)
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[(result.cookie_name, repr(result.inv_cost)) for result in query]
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#+END_SRC
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#+RESULTS[2ce8116fbd2ec77937a191730c2536005f9ac130]:
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| chocolate chip | Decimal('6.00') |
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| dark chocolate chip | Decimal('0.75') |
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| molasses | Decimal('0.80') |
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| peanut butter | Decimal('6.00') |
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| oatmeal raisin | Decimal('100.00') |
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**** Conjunctions
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#+BEGIN_SRC python :table
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query = session.query(Cookie).filter(Cookie.quantity > 23, Cookie.unit_cost < 0.40)
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[(result.cookie_name,) for result in query]
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#+END_SRC
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#+RESULTS[419334c901cd5a42e1b7bf59d3ba8a8b421cca81]:
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| peanut butter |
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#+BEGIN_SRC python :table
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from sqlalchemy import and_, or_, not_
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query = session.query(Cookie).filter(
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or_(Cookie.quantity.between(10, 50), Cookie.cookie_name.contains("chip"))
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)
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[(result.cookie_name,) for result in query]
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#+END_SRC
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#+RESULTS[f1cb32abbfcf01a6b29078b44c8cddf396180df9]:
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| chocolate chip |
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| dark chocolate chip |
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| peanut butter |
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*** Updating Data
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#+BEGIN_SRC python :results value
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query = session.query(Cookie)
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cc_cookie = query.filter(Cookie.cookie_name == "chocolate chip").first()
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cc_cookie.quantity = cc_cookie.quantity + 120
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session.commit()
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cc_cookie.quantity
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#+END_SRC
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#+RESULTS[457d95f641df08c05b2a22152eb07da84eb2d44e]:
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: 132
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#+BEGIN_SRC python :results value
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query = session.query(Cookie)
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query = query.filter(Cookie.cookie_name == "chocolate chip")
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query.update({Cookie.quantity: Cookie.quantity - 20})
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cc_cookie = query.first()
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cc_cookie.quantity
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#+END_SRC
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#+RESULTS[746058c87e4012a5ce9ced0b2378ce48f9991d8c]:
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: 112
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*** Deleting Data
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#+BEGIN_SRC python :results value
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query = session.query(Cookie)
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query = query.filter(Cookie.cookie_name == "dark chocolate chip")
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# Гарантируем, что такая запись только одна,
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# и только она одна будет удалена
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dcc_cookie = query.one()
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session.delete(dcc_cookie)
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session.commit()
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dcc_cookie = query.first()
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# Здесь должен быть None
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assert dcc_cookie is None
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#+END_SRC
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#+RESULTS[61c6636ec27b672253b640a4609f3a229eec09c6]:
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: None
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#+BEGIN_SRC python :results value
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query = session.query(Cookie)
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query = query.filter(Cookie.cookie_name == "molasses")
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query.delete()
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# Убедимся, что больше такой записи нет
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mol_cookie = query.first()
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# Вернёт None
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assert mol_cookie is None
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#+END_SRC
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#+RESULTS[c28ab2893e1da785db9221a9f016ecaea39a7e91]:
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: None
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*** Relations
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#+BEGIN_SRC python :results none
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cookiemon = User(
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username="cookiemon",
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email_address="mon@cookie.com",
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phone="111-111-1111",
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password="password",
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)
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cakeeater = User(
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username="cakeeater",
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email_address="cakeeater@cake.com",
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phone="222-222-2222",
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password="password",
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)
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pieperson = User(
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username="pieperson",
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email_address="person@pie.com",
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phone="333-333-3333",
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password="password",
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)
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session.add(cookiemon)
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session.add(cakeeater)
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session.add(pieperson)
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session.commit()
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#+END_SRC
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#+BEGIN_SRC python :results none
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o1 = Order()
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o1.user = cookiemon
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session.add(o1)
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cc = session.query(Cookie).filter(Cookie.cookie_name == "chocolate chip").one()
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line1 = LineItem(cookie=cc, quantity=2, extended_cost=1.00)
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pb = session.query(Cookie).filter(Cookie.cookie_name == "peanut butter").one()
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line2 = LineItem(quantity=12, extended_cost=3.00)
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line2.cookie = pb
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line2.order = o1
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o1.line_items.append(line1)
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o1.line_items.append(line2)
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session.commit()
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#+END_SRC
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#+BEGIN_SRC python :results none
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o2 = Order()
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o2.user = cakeeater
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cc = session.query(Cookie).filter(Cookie.cookie_name == "chocolate chip").one()
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line1 = LineItem(cookie=cc, quantity=24, extended_cost=12.00)
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oat = session.query(Cookie).filter(Cookie.cookie_name == "oatmeal raisin").one()
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line2 = LineItem(cookie=oat, quantity=6, extended_cost=6.00)
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o2.line_items.append(line1)
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o2.line_items.append(line2)
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session.add(o2)
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session.commit()
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#+END_SRC
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