Remove Python 2 support. Adds ListKnob

setup.cfg

@@ -9,12 +9,28 @@ commit = True
 
 [bumpversion:file:docs/conf.py]
 
-[flake8]
-max-line-length = 160
-
 [tool:pytest]
 norecursedirs = dist build .tox
 
 [bdist_wheel]
 universal = 1
 
+[flake8]
+max-line-length = 120
+exclude = .tox,.git,*/migrations/*,*/static/CACHE/*,docs,node_modules
+
+[pycodestyle]
+max-line-length = 120
+exclude = .tox,.git,*/migrations/*,*/static/CACHE/*,docs,node_modules
+
+[yapf]
+based_on_style = pep8
+column_limit = 120
+dedent_closing_brackets = true
+coalesce_brackets = false
+each_dict_entry_on_separate_line = true
+split_complex_comprehension = true
+
+[importmagic]
+multiline = 'parentheses'
+max_columns = 120

src/environment.py

@@ -1,10 +1,7 @@
-# -*- coding: utf-8 -*-
-# forked adapted and merged from
+# forked, adapted and merged from
 # https://github.com/theskumar/python-dotenv
 # https://github.com/mattseymour/python-env
 
-from __future__ import absolute_import
-
 import codecs
 import os
 import re
@@ -31,7 +28,7 @@ def load_dotenv(dotenv_path, verbose=False):
     """
     if not os.path.exists(dotenv_path):
         if verbose:
-            warnings.warn("Not loading {}, it doesn't exist.".format(dotenv_path))
+            warnings.warn(f"Not loading {dotenv_path}, it doesn't exist.")
         return None
     for k, v in dotenv_values(dotenv_path).items():
         os.environ.setdefault(k, v)
@@ -51,16 +48,14 @@ def get_key(dotenv_path, key_to_get, verbose=False):
     key_to_get = str(key_to_get)
     if not os.path.exists(dotenv_path):
         if verbose:
-            warnings.warn("Can't read {}, it doesn't exist.".format(dotenv_path))
+            warnings.warn(f"Can't read {dotenv_path}, it doesn't exist.")
         return None
     dotenv_as_dict = dotenv_values(dotenv_path)
     if key_to_get in dotenv_as_dict:
         return dotenv_as_dict[key_to_get]
     else:
         if verbose:
-            warnings.warn("key {key} not found in {path}.".format(
-                key=key_to_get, path=dotenv_path)
-            )
+            warnings.warn(f"key {key_to_get} not found in {dotenv_path}.")
         return None
 
 
@@ -69,7 +64,7 @@ def set_key(dotenv_path, key_to_set, value_to_set, quote_mode='always', verbose=
     Adds or Updates a key/value to the given .env
 
     If the .env path given doesn't exist, fails instead of risking creating
-    an orphan .env somewhere in the filesystem
+    an orphan .env somewhere in the file-system
 
     :param dotenv_path: env path
     :param key_to_set: key
@@ -82,7 +77,7 @@ def set_key(dotenv_path, key_to_set, value_to_set, quote_mode='always', verbose=
     value_to_set = str(value_to_set).strip("'").strip('"')
     if not os.path.exists(dotenv_path):
         if verbose:
-            warnings.warn("Can't write to {}, it doesn't exist.".format(dotenv_path))
+            warnings.warn(f"Can't write to {dotenv_path}, it doesn't exist.")
         return None, key_to_set, value_to_set
 
     dotenv_as_dict = OrderedDict(parse_dotenv(dotenv_path))
@@ -108,16 +103,14 @@ def unset_key(dotenv_path, key_to_unset, quote_mode='always', verbose=False):
     key_to_unset = str(key_to_unset)
     if not os.path.exists(dotenv_path):
         if verbose:
-            warnings.warn("Can't delete from {}, it doesn't exist.".format(dotenv_path))
+            warnings.warn(f"Can't delete from {dotenv_path}, it doesn't exist.")
         return None, key_to_unset
     dotenv_as_dict = dotenv_values(dotenv_path)
     if key_to_unset in dotenv_as_dict:
         dotenv_as_dict.pop(key_to_unset, None)
     else:
         if verbose:
-            warnings.warn("Key {key} not removed from {path}, key doesn't exist.".format(
-                key=key_to_unset, path=dotenv_path)
-            )
+            warnings.warn(f"Key {key_to_unset} not removed from {dotenv_path}, key doesn't exist.")
         return None, key_to_unset
 
     success = flatten_and_write(dotenv_path, dotenv_as_dict, quote_mode)
@@ -190,20 +183,17 @@ def _get_format(value, quote_mode='always'):
     Returns the quote format depending on the quote_mode.
     This determines if the key value will be quoted when written to
     the env file.
-    
-    :param value: 
-    :param quote_mode: 
+
+    :param value:
+    :param quote_mode:
     :return: str
     :raises: KeyError if the quote_mode is unknown
     """
 
-    formats = {
-        'always': '{key}="{value}"\n',
-        'auto': '{key}={value}\n'
-    }
+    formats = {'always': '{key}="{value}"\n', 'auto': '{key}={value}\n'}
 
     if quote_mode not in formats.keys():
-        return KeyError('quote_mode {} is invalid'.format(quote_mode))
+        return KeyError(f'quote_mode {quote_mode} is invalid')
 
     _mode = quote_mode
     if quote_mode == 'auto' and ' ' in value:

src/knobs.py

@@ -1,7 +1,6 @@
-from __future__ import absolute_import
-
 import os
 import sys
+import json
 
 import click
 import tabulate
@@ -13,7 +12,7 @@
 BOOLEAN_TRUE_STRINGS = ('true', 'on', 'ok', 'y', 'yes', '1')
 
 
-class Knob(object):
+class Knob:
     """
     A knob can be tuned to satisfaction. Lookup and _cast environment variables to
     the required type.
@@ -38,7 +37,14 @@ class Knob(object):
 
     _register = {}
 
-    def __init__(self, env_name, default, unit='', description='', validator=None):
+    def __init__(
+        self,
+        env_name: str,
+        default,
+        unit: str = '',
+        description: str = '',
+        validator=None,
+    ):
         """
         :param env_name: Name of environment variable
         :param default: Default knob setting
@@ -70,7 +76,7 @@ def help(self):
         """
         :return: Description string with default appended
         """
-        return '{}, Default: {}{}'.format(self.description, self.get(), self.unit)
+        return f'{self.description}, Default: {self.get()}{self.unit}'
 
     def rm(self):
         """
@@ -120,14 +126,13 @@ def get(self):
         return val
 
     def __repr__(self):
-        return "{_class}('{env_name}', {default}, unit={unit}, description='{desc}', validator={validator})".format(
-            _class=self.__class__.__name__,
-            env_name=self.env_name,
-            default=repr(self.default),
-            unit=repr(self.unit),
-            desc=self.description,
-            validator=repr(self.validator),
-        )
+        _class = self.__class__.__name__
+        env_name = self.env_name
+        default = repr(self.default)
+        unit = repr(self.unit)
+        desc = self.description
+        validator = repr(self.validator)
+        return f"{_class}('{env_name}', {default}, unit={unit}, description='{desc}', validator={validator})"
 
     @classmethod
     def get_registered_knob(cls, name):
@@ -145,7 +150,6 @@ def print_knobs_table(cls, ctx, param, value):
         click.echo(cls.get_knob_defaults_as_table())
         ctx.exit()
 
-
     @classmethod
     def get_knob_defaults_as_table(cls):
         """
@@ -158,8 +162,7 @@ def get_knob_defaults_as_table(cls):
                 'Knob': name,
                 'Description': cls.get_registered_knob(name).description,
                 'Default': cls.get_registered_knob(name).default
-            }
-            for name in sorted(cls._register.keys())
+            } for name in sorted(cls._register.keys())
         ]
         return tabulate.tabulate(knob_list, headers='keys', tablefmt='fancy_grid')
 
@@ -172,15 +175,67 @@ def print_knobs_env(cls, ctx, param, value):
 
     @classmethod
     def get_knob_defaults(cls):
-        r""" Returns a string with defaults
+        """ Returns a string with defaults
         >>> Knob.get_knob_defaults()
         '# \n# HAVE_RUM=True\n\n# Yar\n# JOLLY_ROGER_PIRATES=124\n\n# Foo Bar\n# WUNDER=BAR\n'
         """
 
         return '\n'.join(
-            ['# {description}\n# {knob}={default}\n'.format(
-                description=cls.get_registered_knob(name).description,
-                knob=name,
-                default=cls.get_registered_knob(name).default)
-                for name in sorted(cls._register.keys())]
+            [
+                '# {description}\n# {knob}={default}\n'.format(
+                    description=cls.get_registered_knob(name).description,
+                    knob=name,
+                    default=cls.get_registered_knob(name).default
+                ) for name in sorted(cls._register.keys())
+            ]
         )
+
+
+class ListKnob(Knob):
+    """
+    A specialised Knob that expects its value to be a json list environment variable like:
+    ENV_LIST_EXAMPLE='["Foo", "bar"]'
+    """
+
+    def __init__(
+        self,
+        env_name: str,
+        default,
+        unit: str = '',
+        description: str = '',
+        validator=None,
+    ):
+        """
+        :param env_name: Name of environment variable
+        :param default: Default knob setting
+        :param unit: Unit description
+        :param description: What does this knob do
+        :param validator: Callable to validate value
+        """
+
+        # the default's type sets the python type of the value
+        # retrieved from the environment
+        self._cast = type([])
+
+        super().__init__(env_name, default, unit, description, validator)
+
+    def get(self):
+        """
+        convert json env variable if set to list
+        """
+        source_value = os.getenv(self.env_name)
+        # set the environment if it is not set
+        if source_value is None:
+            os.environ[self.env_name] = str(self.default)
+            return self.default
+
+        try:
+            val = json.loads(source_value)
+        except ValueError as e:
+            click.secho(e.message, err=True, color='red')
+            sys.exit(1)
+
+        if self.validator:
+            val = self.validator(val)
+
+        return val