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Active-Alchemy

Version 1.x.x*

Active-Alchemy is wrapper around SQLAlchemy that makes it simple to use your models in an active record like manner, while it still uses the SQLAlchemy db.session underneath.

Active-Alchemy was created as solution to use my flask's application's model without the need to use Flask-SQLAlchemy outside of Flask projects.

What you may like about Active-Alchemy:

Quick Overview:

Create the model

from active_alchemy import ActiveAlchemy

db = ActiveAlchemy('sqlite://')

class User(db.Model):
	name = db.Column(db.String(25))
	location = db.Column(db.String(50), default="USA")
	last_access = db.Column(db.Datetime)

Retrieve all records

for user in User.query():
    print(user.name)

Create new record

user = User.create(name="Mardix", location="Moon")

# or

user = User(name="Mardix", location="Moon").save()

Get a record by primary key (id)

user = User.get(1234)

Update record from primary key

user = User.get(1234)
if user:
	user.update(location="Neptune")

Update record from query iteration

for user in User.query():
	user.update(last_access=db.utcnow());

Soft Delete a record

user = User.get(1234)
if user:
	user.delete()

Query Records

users = User.query(User.location.distinct())

for user in users:
    ...

Query with filter

all = User.query().filter(User.location == "USA")

for user in users:
    ...

How to use

Install

pip install active_alchemy

Create a connection

The ActiveAlchemy class is used to instantiate a SQLAlchemy connection to a database.

from active_alchemy import ActiveAlchemy

db = ActiveAlchemy(dialect+driver://username:password@host:port/database)

Databases Drivers & DB Connection examples

Active-Alchemy comes with a PyMySQL and PG8000 as drivers for MySQL and PostgreSQL respectively, because they are in pure Python. But you can use other drivers for better performance. SQLite is already built in Python.

SQLite:

from active_alchemy import ActiveAlchemy

db = ActiveAlchemy("sqlite://") # in memory

# or 

db = ActiveAlchemy("sqlite:///foo.db") # DB file

PostgreSql:

from active_alchemy import ActiveAlchemy

db = ActiveAlchemy("postgresql+pg8000://user:password@host:port/dbname")

PyMySQL:

from active_alchemy import ActiveAlchemy

db = ActiveAlchemy("mysql+pymysql://user:password@host:port/dbname")

Active-Alchemy also provides access to all the SQLAlchemy functions from the sqlalchemy and sqlalchemy.orm modules. So you can declare models like the following examples:

Create a Model

To start, create a model class and extends it with db.Model

# mymodel.py

from active_alchemy import ActiveAlchemy

db = ActiveAlchemy("sqlite://")

class MyModel(db.Model):
	name = db.Column(db.String(25))
	is_live = db.Column(db.Boolean, default=False)
	
# Put at the end of the model module to auto create all models
db.create_all()

Models: db.Model

db.Model extends your model with helpers that turn your model into an active record like model. But underneath, it still uses the db.session

db.Model also adds a few preset columns on the table:

id: The primary key

created_at: Datetime. It contains the creation date of the record

updated_at: Datetime. It is updated whenever the record is updated.

deleted_at: Datetime. Contains the datetime the record was soft-deleted.

is_deleted: Boolean. A flag to set if record is soft-deleted or not

-- About Soft Delete --

By definition, soft-delete marks a record as deleted so it doesn't get queried, but it still exists in the database. To actually delete the record itself, a hard delete must apply.

By default, when a record is deleted, Active-Alchemy actually sets is_deleted to True and excludes it from being queried, and deleted_at is also set. But this happens only when using the method db.Model.delete().

When a record is soft-deleted, you can also undelete a record by doing: db.Model.delete(False)

Now, to completely delete off the table, db.Model.delete(hard_delete=True)

-- Querying with db.Model.query() --

Due to the fact that Active-Alchemy has soft-delete, to query a model without the soft-deleted records, you must query your model by using the all(*args, **kwargs) which returns a db.session.query object for you to apply filter on etc.

-- db.BaseModel --

By default db.Model adds several preset columns on the table, if you don't want to have them in your model, you can use instead db.BaseModel, which still give you access to the methods to query your model.

BaseModel by default assumes that your primary key is id, but it

class MyExistingModel(db.BaseModel):
    __tablename__ = "my_old_table"
    __primary_key__  = "my_pk_id"
    
    my_pk_id = db.Column(db.Integer, primary_key=True)
    name = db.Column(db.String)
    ...

db.Model Methods Description

query(*args, **kwargs)

To start querying the DB and returns a db.session.query object to filter or apply more conditions.

for user in User.query():
	print(user.login)

By default query() will show only all non-soft-delete records. To display both deleted and non deleted items, add the arg: include_deleted=True

for user in User.query(include_deleted=True):
	print(user.login)

To select columns...

for user in User.query(User.name.distinct(), User.location):
	print(user.login)

To use with filter...

all = User
        .query(User.name.distinct, User.location)
        .order_by(User.updated_at.desc())
        .filter(User.location == "Charlotte")

get(id)

Get one record by id. By default it will query only a record that is not soft-deleted

id = 1234
user = User.get(id)
print(user.id)
print(user.login)

To query a record that has been soft deleted, just set the argument include_deleted=True

id = 234
user = User.get(id, include_deleted=True)

create(**kwargs)

To create/insert new record. Same as init, but just a shortcut to it.

record = User.create(login='abc', passw_hash='hash', profile_id=123)
print (record.login) # -> abc

or you can use the init with save()

record = User(login='abc', passw_hash='hash', profile_id=123).save()
print (record.login) # -> abc

or

record = User(login='abc', passw_hash='hash', profile_id=123)
record.save()
print (record.login) # -> abc

update(**kwargs)

Update an existing record

record = User.get(124)
record.update(login='new_login')
print (record.login) # -> new_login

delete()

To soft delete a record. is_deleted will be set to True and deleted_at datetime will be set

record = User.get(124)
record.delete()
print (record.is_deleted) # -> True

To soft UNdelete a record. is_deleted will be set to False and deleted_at datetime will be None

record = User.get(124)
record.delete(delete=False)
print (record.is_deleted) # -> False

To HARD delete a record. The record will be deleted completely

record = User.get(124)
record.delete(hard_delete=True)

save()

A shortcut to session.add + session.commit()

record = User.get(124)
record.login = "Another one"
record.save()

Method Chaining

For convenience, some method chaining are available

user = User(name="Mardix", location="Charlotte").save()

User.get(12345).update(location="Atlanta")

User.get(345).delete().delete(False).update(location="St. Louis")

Aggegated selects

class Product(db.Model):
	name = db.Column(db.String(250))
	price = db.Column(db.Numeric)
	
price_label = db.func.sum(Product.price).label('price')
results = Product.query(price_label)

With Web Application

In a web application you need to call db.session.remove() after each response, and db.session.rollback() if an error occurs. However, if you are using Flask or other framework that uses the after_request and on_exception decorators, these bindings it is done automatically.

For example using Flask, you can do:

app = Flask(__name__)

db = ActiveAlchemy('sqlite://', app=app)

or

db = ActiveAlchemy()

app = Flask(__name__)

db.init_app(app)

More examples

Many databases, one web app

app = Flask(__name__)
db1 = ActiveAlchemy(URI1, app)
db2 = ActiveAlchemy(URI2, app)

Many web apps, one database

db = ActiveAlchemy(URI1)

app1 = Flask(__name__)
app2 = Flask(__name__)
db.init_app(app1)
db.init_app(app2)

Pagination

All the results can be easily paginated

users = User.paginate(page=2, per_page=20)
print(list(users))  # [User(21), User(22), User(23), ... , User(40)]

The paginator object it's an iterable that returns only the results for that page, so you use it in your templates in the same way than the original result:

{% for item in paginated_items %}
    <li>{{ item.name }}</li>
{% endfor %}

Rendering the pages

Below your results is common that you want it to render the list of pages.

The paginator.pages property is an iterator that returns the page numbers, but sometimes not all of them: if there are more than 11 pages, the result will be one of these, depending of what is the current page:

Skipped page numbers are represented as None.

How many items are displayed can be controlled calling paginator.iter_pages instead.

This is one way how you could render such a pagination in your templates:

{% macro pagination(paginator, endpoint=None, class_='pagination') %}
    {% if not endpoint %}
        {% set endpoint = request.endpoint %}
    {% endif %}
    {% if "page" in kwargs %}
        {% do kwargs.pop("page") %}
    {% endif %}
    <nav>
        <ul class="{{ class_ }}">
          {%- if paginator.has_prev %}
            <li><a href="{{ url_for(endpoint, page=paginator.prev_page_number, **kwargs) }}"
             rel="me prev"><span aria-hidden="true">&laquo;</span></a></li>
          {% else %}
            <li class="disabled"><span><span aria-hidden="true">&laquo;</span></span></li>
          {%- endif %}

          {%- for page in paginator.pages %}
            {% if page %}
              {% if page != paginator.page %}
                <li><a href="{{ url_for(endpoint, page=page, **kwargs) }}"
                 rel="me">{{ page }}</a></li>
              {% else %}
                <li class="active"><span>{{ page }}</span></li>
              {% endif %}
            {% else %}
              <li><span class=ellipsis>…</span></li>
            {% endif %}
          {%- endfor %}

          {%- if paginator.has_next %}
            <li><a href="{{ url_for(endpoint, page=paginator.next_page_number, **kwargs) }}"
             rel="me next">»</a></li>
          {% else %}
            <li class="disabled"><span aria-hidden="true">&raquo;</span></li>
          {%- endif %}
        </ul>
    </nav>
{% endmacro %}

Credits:

SQLAlchemy

Flask-SQLAlchemy

SQLAlchemy-Wrapper

Paginator

Arrow

SQLAlchemy-Utils

copyright: 2015-2016

license: MIT, see LICENSE for more details.