Apply some refurb suggestions

src/packaging/_parser.py

@@ -324,10 +324,7 @@ def _parse_marker_var(tokenizer: Tokenizer) -> MarkerVar:
 
 
 def process_env_var(env_var: str) -> Variable:
-    if (
-        env_var == "platform_python_implementation"
-        or env_var == "python_implementation"
-    ):
+    if env_var in ("platform_python_implementation", "python_implementation"):
         return Variable("platform_python_implementation")
     else:
         return Variable(env_var)

src/packaging/requirements.py

@@ -38,7 +38,7 @@ def __init__(self, requirement_string: str) -> None:
 
         self.name: str = parsed.name
         self.url: Optional[str] = parsed.url or None
-        self.extras: Set[str] = set(parsed.extras if parsed.extras else [])
+        self.extras: Set[str] = set(parsed.extras or [])
         self.specifier: SpecifierSet = SpecifierSet(parsed.specifier)
         self.marker: Optional[Marker] = None
         if parsed.marker is not None:

src/packaging/specifiers.py

@@ -11,17 +11,7 @@
 import abc
 import itertools
 import re
-from typing import (
-    Callable,
-    Iterable,
-    Iterator,
-    List,
-    Optional,
-    Set,
-    Tuple,
-    TypeVar,
-    Union,
-)
+from typing import Callable, Iterable, Iterator, List, Optional, Tuple, TypeVar, Union
 
 from .utils import canonicalize_version
 from .version import Version
@@ -697,7 +687,10 @@ def _pad_version(left: List[str], right: List[str]) -> Tuple[List[str], List[str
     left_split.insert(1, ["0"] * max(0, len(right_split[0]) - len(left_split[0])))
     right_split.insert(1, ["0"] * max(0, len(left_split[0]) - len(right_split[0])))
 
-    return (list(itertools.chain(*left_split)), list(itertools.chain(*right_split)))
+    return (
+        list(itertools.chain.from_iterable(left_split)),
+        list(itertools.chain.from_iterable(right_split)),
+    )
 
 
 class SpecifierSet(BaseSpecifier):
@@ -729,14 +722,8 @@ def __init__(
         # strip each item to remove leading/trailing whitespace.
         split_specifiers = [s.strip() for s in specifiers.split(",") if s.strip()]
 
-        # Parsed each individual specifier, attempting first to make it a
-        # Specifier.
-        parsed: Set[Specifier] = set()
-        for specifier in split_specifiers:
-            parsed.add(Specifier(specifier))
-
-        # Turn our parsed specifiers into a frozen set and save them for later.
-        self._specs = frozenset(parsed)
+        # Make each individual specifier a Specifier and save in a frozen set for later.
+        self._specs = frozenset(map(Specifier, split_specifiers))
 
         # Store our prereleases value so we can use it later to determine if
         # we accept prereleases or not.

tests/test_specifiers.py

@@ -235,8 +235,7 @@ def test_specifiers_hash(self, specifier):
 
     @pytest.mark.parametrize(
         ("left", "right", "op"),
-        itertools.chain(
-            *
+        itertools.chain.from_iterable(
             # Verify that the equal (==) operator works correctly
             [[(x, x, operator.eq) for x in SPECIFIERS]]
             +
@@ -260,8 +259,7 @@ def test_comparison_canonicalizes(self, left, right):
 
     @pytest.mark.parametrize(
         ("left", "right", "op"),
-        itertools.chain(
-            *
+        itertools.chain.from_iterable(
             # Verify that the equal (==) operator works correctly
             [[(x, x, operator.ne) for x in SPECIFIERS]]
             +
@@ -815,8 +813,7 @@ def test_specifiers_combine_not_implemented(self):
 
     @pytest.mark.parametrize(
         ("left", "right", "op"),
-        itertools.chain(
-            *
+        itertools.chain.from_iterable(
             # Verify that the equal (==) operator works correctly
             [[(x, x, operator.eq) for x in SPECIFIERS]]
             +
@@ -836,8 +833,7 @@ def test_comparison_true(self, left, right, op):
 
     @pytest.mark.parametrize(
         ("left", "right", "op"),
-        itertools.chain(
-            *
+        itertools.chain.from_iterable(
             # Verify that the equal (==) operator works correctly
             [[(x, x, operator.ne) for x in SPECIFIERS]]
             +

tests/test_version.py

@@ -667,8 +667,7 @@ def test_version_is_postrelease(self, version, expected):
         ("left", "right", "op"),
         # Below we'll generate every possible combination of VERSIONS that
         # should be True for the given operator
-        itertools.chain(
-            *
+        itertools.chain.from_iterable(
             # Verify that the less than (<) operator works correctly
             [
                 [(x, y, operator.lt) for y in VERSIONS[i + 1 :]]
@@ -710,8 +709,7 @@ def test_comparison_true(self, left, right, op):
         ("left", "right", "op"),
         # Below we'll generate every possible combination of VERSIONS that
         # should be False for the given operator
-        itertools.chain(
-            *
+        itertools.chain.from_iterable(
             # Verify that the less than (<) operator works correctly
             [
                 [(x, y, operator.lt) for y in VERSIONS[: i + 1]]