SimpleQuery

query from containers of objects, in Python

Query pattern

The Query pattern uses criteria on classes and fields to retrieve value objects from a dataset. Those criteria are a field, an operator, and a value. For example, ('last_name', =, 'Fowler') or ('price', <, 100.00).

Installation

pip install simple-query

Usage

all() returns the matching objects for a query, and filter(*criteria) returns a new, filtered query, where criteria = field, operator, value.

For example:

from simple_query.query import Query
from operator import eq, gt, lt

people = [
    Person('Ada Lovelace'),
    Person('Grace Hopper'),
    Person('Jean Bartik')]

Query(people).all()
# [Person('Ada Lovelace'), Person('Grace Hopper'), Person('Jean Bartik')]

Query(people).filter('last_name', eq, 'Lovelace').all()
# [Person('Ada Lovelace')]

Query(people) \
    .filter('first_name', gt, 'B') \
    .filter('last_name', lt, 'C').all()
# [Person('Jean Bartik')]

Setting up development environment

It is always recommended to use a virtual environment for each Python appplication. Create the environment once, after cloning this repository to your machine.

python3 -m venv .env

For each terminal session going forward, work on the virtual environment and use its copy of python.

source .env/bin/activate

Upgrade pip

pip install -U pip

Install developer requirements for a nicer test runner (see Running Tests)

pip install -r requirements/dev.txt

Running tests

Tests are written in unittest syntax, so no additional package are needed to run them

python -m unittest discover

For a more informative output, as well as plugins for color and watch mode, use nose test runner. You can also use the test runner of your choice.

nosetests --rednose --with-watch