birch 0.0.3

Utilities for pandas.

birch |birch_icon|
##########
|PyPI-Status| |PyPI-Versions| |Build-Status| |Codecov| |LICENCE|

Simple hierarchical configuration for Python packages.

.. |birch_icon| image:: https://github.com/shaypal5/birch/blob/cc5595bbb78f784a3174a07157083f755fc93172/birch.png
:height: 87
:width: 40 px
:scale: 50 %

.. .. image:: https://github.com/shaypal5/birch/blob/b10a19a28cb1fc41d0c596df5bcd8390e7c22ee7/birch.png

.. code-block:: python

from birch import Birch
cfg = Birch('mypackage')
# read both the MYPACKAGE_SERVER_HOSTNAME environment variable
# and ~/.mypackage/cfg.json containing {'server': {'port': 55}}
connect(cfg['SERVER_HOSTNAME'], cfg['server']['port'])

.. contents::

.. section-numbering::


Installation
============

.. code-block:: bash

pip install birch


Features
========

* Supported formats: JSON, YAML.
* Pure python.
* Supports Python 3.4+.
* Fully tested.


Use
===

Basic use
---------

``birch`` provides a simple way to read simple hierarchical configuration for your Python package or application from both environment variables and configuration files.

``birch`` uses namespaces to manage configuration values. The access to each namespace is done via a ``Birch`` object initialized with that namespace. Though written with a specific use case in mind, where a single package uses a single namespace to manage its configuration, any number of namespaces can be used. For example:

.. code-block:: python

from birch import Birch
zubat_cfg = Birch('zubat')
golbat_cfg = Birch('golbat')


Each namespace encompasses all values set by either environment variables starting with ``<uppercase_namespace>_``, or defined within ``cfg`` files (of a supported format) located in the ``~/.<namespace>`` directory.

For example, the ``zubat`` namespace encompasses environment variables such as ``ZUBAT_HOSTNAME`` and ``ZUBAT_PORT``, and all mappings in the ``~/.zubat/cfg.json`` file (if it exists).

Once defined in such a way, the ``Birch`` object can be used to access the values of mappings of both types (with or without the namespace suffix; casing is also ignored). For example:

.. code-block:: python

>>> os.environ['ZUBAT_SERVER_HOST'] = 'www.zubat.com'
>>> os.environ['ZUBAT_SERVER_PORT'] = '87'
>>> from birch import Birch
>>> zubat_cfg = Birch('zubat')
>>>> zubat_cfg['ZUBAT_SERVER_HOST']
'www.zubat.com'
>>> zubat_cfg['SERVER_PORT']
'87'
>>> zubat_cfg['server_port']
'87'


Hierarchical configuration
--------------------------

``birch`` supports a simple hierarchy between configuration mappings. The ``_`` character is used to signal a hierarchical mapping, so the ``ZUBAT_SERVER_PORT`` environment variable is equivalent to ``{'server': {'port': 55}}`` mapping given in a ``~/.zubat/cfg.json`` file, for example. It is also **partially** equivalent to the ``{'server_port': 55}`` mapping.

As such, hierarchical mapping can be accessed either using ``_`` to indicate a hierarchical path, or using dict-like item access:

.. code-block:: python

>>> os.environ['ZUBAT_SERVER_HOST'] = 'www.zubat.com'
>>> from birch import Birch
>>> zubat_cfg = Birch('zubat')
>>>> zubat_cfg['SERVER_HOST']
'www.zubat.com'
>>>> zubat_cfg['SERVER']['HOST']
'www.zubat.com'


**This is not true for non-hierarchical mappings**; so, ``{'server_port': 55}`` can only be accessed with ``zubat_cfg['SERVER_PORT']``, and not using ``zubat_cfg['SERVER']['PORT']``.

Also, **note that casing is not ignored for levels after the first**, so a mapping given by the ``ZUBAT_SERVER_PORT`` environment variable cannot be read with ``zubat_cfg['server']['port']``, but only with
``zubat_cfg['SERVER']['PORT']`` or ``zubat_cfg['server']['PORT']``.

As such, a good practice is to only use upper-case strings for mapping access, anf not use the ``_`` character within a name in configuration files.


Resolution order
----------------

A namespace is always loaded with matching environment variables **after** all configuration files has been loaded, and corresponding mappings will thus override their file-originating counterparts; e.g. the ``ZUBAT_SERVER_PORT`` environment variable will overwrite the value of the mapping ``{'server': {'port': 55}}`` given in a ``~/.zubat/cfg.json`` file.

The loading order of different files, while deterministic, is undefined and not part of the API. Thus, ``cfg`` files with different file extensions can not be relied upon to provide private-vs-shared configuration functionality.


Configuring birch
-----------------

Configuration directories
~~~~~~~~~~~~~~~~~~~~~~~~~

By default ``birch`` looks for files only in the ``~/.<namespace>`` directory. You can set a different set of directories to read by populating the ``directories`` constructor parameter with a different directory path, or a list of paths.


File formats
~~~~~~~~~~~~

By default, ``birch`` will only try to read ``cfg.json`` files. To dictate a different set of supported format, populate the ``supported_formats`` constructor parameter with the desired formats.

For example, ``Birch('zubat', supported_formats=['json', 'yaml'])`` will read both ``cfg.json`` and ``cfg.yaml`` files, while ``Birch('golbat', supported_formats='yaml')`` will ony read ``cfg.yaml`` (and ``cfg.yml``) files.

Currently supported formats are:
* ``JSON`` - Looks for ``cfg.json`` files.
* ``YAML`` - Looks for ``cfg.yaml`` and ``cfg.yml`` files.


Contributing
============

Package author and current maintainer is Shay Palachy ([e-mail]); You are more than welcome to approach him for help. Contributions are very welcomed.

Installing for development
----------------------------

Clone:

.. code-block:: bash

git clone [e-mail]:shaypal5/birch.git


Install in development mode, including test dependencies:

.. code-block:: bash

cd birch
pip install -e '.[test]'

Or, if you are using ``pipenv``, use the following command to create a ``pipenv`` Python virtual environment with development dependencies:

.. code-block:: bash

cd birch
pipenv install --dev


Running the tests
-----------------

To run the tests use:

.. code-block:: bash

cd birch
pytest

Or, if you are using ``pipenv``:

.. code-block:: bash

cd birch
pipenv run pytest


Adding documentation
--------------------

The project is documented using the `numpy docstring conventions`_, which were chosen as they are perhaps the most widely-spread conventions that are both supported by common tools such as Sphinx and result in human-readable docstrings. When documenting code you add to this project, follow `these conventions`_.

.. _`numpy docstring conventions`: https://github.com/numpy/numpy/blob/master/doc/HOWTO_DOCUMENT.rst.txt
.. _`these conventions`: https://github.com/numpy/numpy/blob/master/doc/HOWTO_DOCUMENT.rst.txt


Credits
=======

Created by `Shay Palachy <http://www.shaypalachy.com/>`_ ([e-mail]).


.. |PyPI-Status| image:: https://img.shields.io/pypi/v/birch.svg
:target: https://pypi.python.org/pypi/birch

.. |PyPI-Versions| image:: https://img.shields.io/pypi/pyversions/birch.svg
:target: https://pypi.python.org/pypi/birch

.. |Build-Status| image:: https://travis-ci.org/shaypal5/birch.svg?branch=master
:target: https://travis-ci.org/shaypal5/birch

.. |LICENCE| image:: https://img.shields.io/github/license/shaypal5/birch.svg
:target: https://github.com/shaypal5/birch/blob/master/LICENSE

.. |Codecov| image:: https://codecov.io/github/shaypal5/birch/coverage.svg?branch=master
:target: https://codecov.io/github/shaypal5/birch?branch=master