Convert to a Python package

.github/workflows/ci.yml

@@ -0,0 +1,31 @@
+name: Python package
+
+on:
+  push:
+    branches: [ master ]
+  pull_request:
+    branches: [ master ]
+
+jobs:
+  build:
+    runs-on: ubuntu-latest
+    steps:
+    - uses: actions/checkout@v2
+    - uses: actions/setup-python@v1
+    - name: Upgrade pip
+      run: python -m pip install --upgrade pip
+    - name: Lint with flake8
+      run: |
+        pip install flake8
+        find . -name "*.py" | flake8 --count --max-complexity=5 \
+                                     --show-source --statistics
+    - name: Install and test with pytest
+      run: |
+        pip install pytest setuptools-scm
+        pip install --editable .
+        pytest --verbose
+    - name: Test package build
+      run: |
+        pip install twine wheel
+        python3 setup.py bdist_wheel sdist
+        twine check dist/*

.gitignore

@@ -1,4 +1,10 @@
+# Python
+*.egg-info
 __pycache__
 .benchmarks
 .pytest_cache
+build
+dist
+
+# Editors
 .idea/*

AUTHORS

@@ -0,0 +1,3 @@
+Paul Natsuo Kishimoto <kishimot@iiasa.ac.at> (@khaeru, IIASA)
+Daniel Huppmann <huppmann@iiasa.ac.at> (@danielhuppmann, IIASA)
+Franceso Lovat <lovat@iiasa.ac.at> (@francescolovat, IIASA)

DEVELOPING.rst

@@ -0,0 +1,38 @@
+Development notes
+*****************
+
+The repository and package aim to be ruthlessly simple, and thus as easy as possible to maintain.
+Thus:
+
+- No built documentation; like `pycountry <https://pypi.org/project/pycountry/>`_, the README *is* the documentation.
+- Actual code (in \_\_init\_\_.py) kept to a minimum.
+- `setuptools-scm <https://pypi.org/project/setuptools-scm/>`_ and git tags used for all versioning.
+- Minimal CI configuration: one service/OS/Python version.
+- Versioning: similar to pycountry: ``<YYYY>.<M>.<D>``.
+- AUTHORS: anyone adding a commit to the repo should also add their name to AUTHORS.
+
+
+Test the package build
+======================
+
+.. code-block:: shell
+
+   $ rm -r build dist
+   $ python3 setup.py bdist_wheel sdist
+   $ twine check dist/
+
+Ensure there are no warnings from twine.
+
+
+Generated data files for GWP contexts
+=====================================
+
+iam_units/data/emissions/emissions.txt defines the base units for Pint, and imports the files iam_units/data/emissions/gwp\_\*.txt.
+These files each define one context, and contain a notice that they should not be edited manually.
+
+Update these files using the command::
+
+    $ python -m iam_units.update emissions
+
+The update submodule parses metric_conversions.csv and writes the context files.
+When adding a new context file, make sure to ``@import`` it in emissions.txt and write a unit test.

README.rst

@@ -0,0 +1,122 @@
+Unit definitions for integrated-assessment research
+***************************************************
+
+© 2020 `IAM-units authors`_; licensed under the `GNU GPL version 3`_.
+
+The file `definitions.txt`_ gives `Pint`_-compatible definitions of energy, climate, and related units to supplement the SI and other units included in Pint's `default_en.txt`_.
+These definitions are used by:
+
+- the IIASA Energy Program `MESSAGEix-GLOBIOM`_ integrated assessment model (IAM),
+- the Python package `pyam`_ for analysis and visualization of integrated-assessment scenarios (see `pyam.IamDataFrame.convert_unit()`_ for details)
+
+and may be used for research in integrated assessment, energy systems, transportation, or other, related fields.
+(Please open a `pull request`_ to add your usage to this README!)
+
+Usage
+=====
+
+.. code-block:: python
+
+    >>> from iam_units import registry
+
+    >>> qty = registry('1.2 tce')
+    >>> qty
+    1.2 <Unit('tonne_of_coal_equivalent')>
+
+    >>> qty.to('GJ')
+    29.308 <Unit('gigajoule')>
+
+To make the ``registry`` from this package the default:
+
+.. code-block:: python
+
+    >>> import pint
+    >>> pint.set_application_registry(registry)
+
+    # Now used by default for pint top-level classes and methods
+    >>> pint.Quantity('1.2 tce')
+    1.2 <Unit('tonne_of_coal_equivalent')>
+
+Warnings
+========
+
+``iam_units`` overwrites Pint's default definitions in the following cases:
+
+.. list-table::
+   :header-rows: 1
+
+   - - ``pint`` default
+     - ``iam_units``
+     - Note
+   - - 'C' = Coulomb
+     - 'C' = carbon
+     - See `emissions.txt`_ at line 10.
+
+Technical details
+=================
+
+Emissions and GWP
+-----------------
+
+`emissions.txt`_ defines some greenhouse gases (GHGs) as Pint base units.
+Conversion of masses of these GHGs to CO₂ equivalents use selectable global warming potential (GWP) metrics, implemented as Pint `contexts`_ in the other files in the same directory.
+The contexts have names like ``gwp_<IPCC report>GWP<years>``, where ``<years>`` is `100` and:
+
+.. list-table::
+   :header-rows: 1
+
+   - - ``<IPCC report>``
+     - Meaning
+   - - ``SAR``
+     - Second Assessment Report (1995)
+   - - ``AR4``
+     - Fourth Assessment Report (2007)
+   - - ``AR5``
+     - Fifth Assessment Report (2014)
+
+To use one of these contexts, give its name as the second argument to the ``pint.Quantity.to()`` method:
+
+.. code-block:: python
+
+   >>> qty = registry('3.5e3 t N20')
+   >>> qty
+   3500 <Unit('metric_ton * nitrous_oxide')>
+
+   >>> qty.to('Mt CO2', 'gwp_AR4GWP100')
+   0.9275 <Unit('carbon_dioxide * megametric_ton')>
+
+   # Using a different metric
+   >>> qty.to('Mt CO2', 'gwp_SARGWP100')
+   1.085 <Unit('carbon_dioxide * megametric_ton')>
+
+Data sources
+~~~~~~~~~~~~
+The GWP unit definitions are generated using the file metric_conversions.csv.
+The file is copied from `lewisjared/scmdata`_ v0.4, authored by `@lewisjared <https://github.com/lewisjared>`_, `@swillner <https://github.com/swillner>`_, and `@znicholls <https://github.com/znicholls>`_ and licensed under BSD-3.
+The version in scmdata was transcribed from `this source`_ (PDF link).
+
+See `<DEVELOPING.rst>`_ for details on updating the definitions.
+
+.. _contexts: https://pint.readthedocs.io/en/latest/contexts.html
+.. _lewisjared/scmdata: https://github.com/lewisjared/scmdata/tree/v0.4.0/src/scmdata/data
+.. _this source: https://www.ghgprotocol.org/sites/default/files/ghgp/Global-Warming-Potential-Values%20%28Feb%2016%202016%29_1.pdf
+
+
+Tests and development
+=====================
+
+Use ``pytest iam_units`` to check that the definitions can be loaded.
+Example unit expressions in `checks.csv`_ are also checked.
+See `<DEVELOPING.rst>`_ for further details.
+
+.. _IAM-units authors: ./AUTHORS
+.. _GNU GPL version 3: ./LICENSE
+.. _definitions.txt: ./iam_units/data/definitions.txt
+.. _emissions.txt: ./iam_units/data/emissions/emissions.txt
+.. _checks.csv: ./iam_units/data/checks.csv
+.. _Pint: https://pint.readthedocs.io
+.. _default_en.txt: https://github.com/hgrecco/pint/blob/master/pint/default_en.txt
+.. _MESSAGEix-GLOBIOM: https://message.iiasa.ac.at
+.. _pyam: https://pyam-iamc.readthedocs.io
+.. _pyam.IamDataFrame.convert_unit(): https://pyam-iamc.readthedocs.io/en/stable/api/iamdataframe.html#pyam.IamDataFrame.convert_unit
+.. _pull request: https://github.com/IAMconsortium/units/pulls

iam_units/__init__.py

@@ -0,0 +1,7 @@
+from pathlib import Path
+
+import pint
+
+registry = pint.UnitRegistry()
+registry.load_definitions(
+    str(Path(__file__).parent / 'data' / 'definitions.txt'))

definitions.txt → iam_units/data/definitions.txt

@@ -49,4 +49,4 @@ tkm = tonne_freight * kilometer
 
 # please add any emissions-related definitions to modules/emissions
 
-@import modules/emissions/emissions.txt
+@import emissions/emissions.txt

modules/emissions/emissions.txt → iam_units/data/emissions/emissions.txt

@@ -25,7 +25,7 @@ ammonia = [ammonia] = nh3 = NH3
 sulfur = [sulfur] = S
 
 # Importing contexts to define conversions to co2-equivalents (=co2)
-# see the README of this module for more information
+# See DEVELOPING.rst for more information.
 
 @import gwp_AR5GWP100.txt
 @import gwp_AR4GWP100.txt

modules/emissions/gwp_AR4GWP100.txt → iam_units/data/emissions/gwp_AR4GWP100.txt

@@ -1,4 +1,4 @@
-# This file was created using the script `write_gwp_context.py`
+# This file was generated using python -m iam_units.update emissions
 # DO NOT ALTER THIS FILE MANUALLY!
 
 @context gwp_AR4GWP100
@@ -25,4 +25,4 @@
     [nitrous_oxide] / [time] -> [carbon_dioxide] / [time]: value * 298.0 * CO2 / N2O
     [carbon_dioxide] / [time] -> [nitrous_oxide] / [time]: value / 298.0 * N2O / CO2
 
-@end
+@end

modules/emissions/gwp_AR5GWP100.txt → iam_units/data/emissions/gwp_AR5GWP100.txt

@@ -1,4 +1,4 @@
-# This file was created using the script `write_gwp_context.py`
+# This file was generated using python -m iam_units.update emissions
 # DO NOT ALTER THIS FILE MANUALLY!
 
 @context gwp_AR5GWP100
@@ -25,4 +25,4 @@
     [nitrous_oxide] / [time] -> [carbon_dioxide] / [time]: value * 265.0 * CO2 / N2O
     [carbon_dioxide] / [time] -> [nitrous_oxide] / [time]: value / 265.0 * N2O / CO2
 
-@end
+@end

modules/emissions/gwp_SARGWP100.txt → iam_units/data/emissions/gwp_SARGWP100.txt

@@ -1,4 +1,4 @@
-# This file was created using the script `write_gwp_context.py`
+# This file was generated using python -m iam_units.update emissions
 # DO NOT ALTER THIS FILE MANUALLY!
 
 @context gwp_SARGWP100
@@ -25,4 +25,4 @@
     [nitrous_oxide] / [time] -> [carbon_dioxide] / [time]: value * 310.0 * CO2 / N2O
     [carbon_dioxide] / [time] -> [nitrous_oxide] / [time]: value / 310.0 * N2O / CO2
 
-@end
+@end

test.py → iam_units/test_all.py

@@ -3,16 +3,18 @@
 
 import pint
 from pint.util import UnitsContainer
-
 import pytest
 
+from iam_units import registry
+
 
+DATA_PATH = Path(__file__).parent / 'data'
 defaults = pint.get_application_registry()
 
 
 # Read units to check from file
 PARAMS = []
-with open(Path(__file__).with_name('checks.csv')) as f:
+with open(DATA_PATH / 'checks.csv') as f:
     for row in csv.reader(f, skipinitialspace=True, quoting=csv.QUOTE_MINIMAL):
         try:
             unit_str, dims, new_def = row
@@ -33,17 +35,9 @@
         PARAMS.append((unit_str, dims, new_def))
 
 
-@pytest.fixture(scope='session')
-def registry():
-    """UnitRegistry including definitions from definitions.txt."""
-    reg = pint.UnitRegistry()
-    reg.load_definitions(str(Path(__file__).with_name('definitions.txt')))
-    yield reg
-
-
 @pytest.mark.parametrize('unit_str, dim, new_def', PARAMS,
                          ids=lambda v: v if isinstance(v, str) else '')
-def test_units(registry, unit_str, dim, new_def):
+def test_units(unit_str, dim, new_def):
     if new_def:
         # Units defined in dimensions.txt are not recognized by base pint
         with pytest.raises(pint.UndefinedUnitError):
@@ -60,7 +54,7 @@ def test_units(registry, unit_str, dim, new_def):
                          [('AR5GWP100', 28),
                           ('AR4GWP100', 25),
                           ('SARGWP100', 21)])
-def test_units_emissions(registry, context, value):
+def test_units_emissions(context, value):
     # The registry shouldn't convert with specifying a valid context
     with pytest.raises(pint.DimensionalityError):
         registry['ch4'].to('co2')