feat: Drop Python 2.7 support (#704)

* Drop Python 2.7 support for pyhf
* Add no Python 2.7 support to FAQ and link to last supported release

Author: matthewfeickert

.github/workflows/ci.yml

@@ -14,7 +14,7 @@ jobs:
     strategy:
       matrix:
         os: [ubuntu-latest, macos-latest]
-        python-version: [2.7, 3.6, 3.7]
+        python-version: [3.6, 3.7]
 
     steps:
     - uses: actions/checkout@v1.2.0
@@ -51,7 +51,6 @@ jobs:
         file: ./coverage.xml
         flags: unittests
     - name: Test Contrib module with pytest
-      if: matrix.python-version != 2.7
       run: |
         python -m pytest -r sx tests/contrib --mpl --mpl-baseline-path tests/contrib/baseline
     - name: Run benchmarks

docs/faq.rst

@@ -14,6 +14,26 @@ Use the :code:`--backend` option for :code:`pyhf cls` to specify a tensor backen
 The default backend is NumPy.
 For more information see :code:`pyhf cls --help`.
 
+Does ``pyhf`` support Python 2?
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+No.
+Like the rest of the Python community, as of January 2020 the latest releases of ``pyhf`` no longer support Python 2.
+The last release of ``pyhf`` that was compatible with Python 2.7 is `v0.3.4 <https://pypi.org/project/pyhf/0.3.4/>`__, which can be installed with
+
+    .. code-block:: console
+
+        python -m pip install pyhf~=0.3
+
+I only have access to Python 2. How can I use ``pyhf``?
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+
+It is recommended that ``pyhf`` is used as a standalone step in any analysis, and its environment need not be the same as the rest of the analysis.
+As Python 2 is not supported it is suggested that you setup a Python 3 runtime on whatever machine you're using.
+If you're using a cluster, talk with your system administrators to get their help in doing so.
+If you are unable to get a Python 3 runtime, versioned Docker images of ``pyhf`` are distributed through `Docker Hub <https://hub.docker.com/r/pyhf/pyhf>`__.
+
+Once you have Python 3 installed, see the :ref:`installation` page to get started.
+
 Troubleshooting
 ---------------
 

docs/governance/ROADMAP.md

@@ -66,7 +66,7 @@ The roadmap will be executed over mostly Quarter 3 of 2019 through Quarter 1 of
    - [ ] Add background model support (Issue #514) [2019-Q4 → 2020-Q1]
    - [ ] Develop interface for the optimizers similar to tensor/backend [2019-Q4 → 2020-Q1]
    - [x] Migrate to TensorFlow v2.0 (PR #541) [2019-Q4]
-   - [ ] Drop Python 2.7 support at end of 2019 (Issue #469) [2019-Q4 (last week of December 2019)]
+   - [x] Drop Python 2.7 support at end of 2019 (Issue #469) [2019-Q4 (last week of December 2019)]
    - [ ] Finalize public API [2020-Q1]
    - [ ] Integrate pyfitcore/Statisfactory API [2020-Q1]
 4. **Research**

docs/installation.rst

@@ -1,3 +1,5 @@
+..  _installation:
+
 Installation
 ============
 
@@ -8,12 +10,6 @@ To install, we suggest first setting up a `virtual environment <https://packagin
     # Python3
     python3 -m venv pyhf
 
-
-.. code-block:: console
-
-    # Python2
-    virtualenv --python=$(which python) pyhf
-
 and activating it
 
 .. code-block:: console

pyproject.toml

@@ -5,9 +5,8 @@ build-backend = "setuptools.build_meta"
 
 [tool.black]
 line-length = 88
-py36 = false  # Python 2 is still supported
+target-version = ['py36', 'py37', 'py38']
 skip-string-normalization = true
-skip-numeric-underscore-normalization = true  # Python 2 is still supported
 include = '\.pyi?$'
 exclude = '''
 /(

setup.py

@@ -1,10 +1,7 @@
 from setuptools import setup, find_packages
 from os import path
-import sys
 
 this_directory = path.abspath(path.dirname(__file__))
-if sys.version_info.major < 3:
-    from io import open
 with open(path.join(this_directory, 'README.md'), encoding='utf-8') as readme_md:
     long_description = readme_md.read()
 
@@ -88,16 +85,14 @@
     license='Apache',
     keywords='physics fitting numpy scipy tensorflow pytorch',
     classifiers=[
-        "Programming Language :: Python :: 2",
-        "Programming Language :: Python :: 2.7",
         "Programming Language :: Python :: 3",
         "Programming Language :: Python :: 3.6",
         "Programming Language :: Python :: 3.7",
     ],
     package_dir={'': 'src'},
     packages=find_packages(where='src'),
     include_package_data=True,
-    python_requires=">=2.7, !=3.0.*, !=3.1.*, !=3.2.*, !=3.3.*, !=3.4.*, !=3.5.*",
+    python_requires=">=3.6",
     install_requires=[
         'scipy',  # requires numpy, which is required by pyhf and tensorflow
         'click>=6.0',  # for console scripts,

src/pyhf/cli/rootio.py

@@ -8,14 +8,6 @@
 logging.basicConfig()
 log = logging.getLogger(__name__)
 
-# This is only needed for Python 2/3 compatibility
-def ensure_dirs(path):
-    try:
-        os.makedirs(path, exist_ok=True)  # lgtm [py/call/wrong-named-argument]
-    except TypeError:
-        if not os.path.exists(path):
-            os.makedirs(path)
-
 
 @click.group(name='rootio')
 def cli():
@@ -77,14 +69,14 @@ def json2xml(workspace, output_dir, specroot, dataroot, resultprefix, patch):
         )
     from .. import writexml
 
-    ensure_dirs(output_dir)
+    os.makedirs(output_dir, exist_ok=True)
     with click.open_file(workspace, 'r') as specstream:
         spec = json.load(specstream)
         for pfile in patch:
             patch = json.loads(click.open_file(pfile, 'r').read())
             spec = jsonpatch.JsonPatch(patch).apply(spec)
-        ensure_dirs(os.path.join(output_dir, specroot))
-        ensure_dirs(os.path.join(output_dir, dataroot))
+        os.makedirs(os.path.join(output_dir, specroot), exist_ok=True)
+        os.makedirs(os.path.join(output_dir, dataroot), exist_ok=True)
         with click.open_file(
             os.path.join(output_dir, '{0:s}.xml'.format(resultprefix)), 'w'
         ) as outstream:

src/pyhf/infer/mle.py

@@ -59,5 +59,5 @@ def fixed_poi_fit(poi_val, data, pdf, init_pars=None, par_bounds=None, **kwargs)
         init_pars,
         par_bounds,
         [(pdf.config.poi_index, poi_val)],
-        **kwargs
+        **kwargs,
     )

src/pyhf/optimize/opt_minuit.py

@@ -52,7 +52,7 @@ def f(pars):
             errordef=1,
             use_array_call=True,
             forced_parameters=parnames,
-            **kwargs
+            **kwargs,
         )
         return mm
 

src/pyhf/pdf.py

@@ -287,7 +287,7 @@ def __init__(self, config, mega_mods, nominal_rates, batch_size):
                 config,
                 mega_mods,
                 batch_size=self.batch_size,
-                **config.modifier_settings.get(k, {})
+                **config.modifier_settings.get(k, {}),
             )
             for k, c in modifiers.combined.items()
         }