bpo-30296 Remove unnecessary tuples, lists, sets, and dicts (#1489)

* Replaced list(<generator expression>) with list comprehension
* Replaced dict(<generator expression>) with dict comprehension
* Replaced set(<list literal>) with set literal
* Replaced builtin func(<list comprehension>) with func(<generator
  expression>) when supported (e.g. any(), all(), tuple(), min(), &
  max())

Author: jdufresne

Lib/_weakrefset.py

@@ -157,19 +157,19 @@ def issubset(self, other):
     __le__ = issubset
 
     def __lt__(self, other):
-        return self.data < set(ref(item) for item in other)
+        return self.data < set(map(ref, other))
 
     def issuperset(self, other):
         return self.data.issuperset(ref(item) for item in other)
     __ge__ = issuperset
 
     def __gt__(self, other):
-        return self.data > set(ref(item) for item in other)
+        return self.data > set(map(ref, other))
 
     def __eq__(self, other):
         if not isinstance(other, self.__class__):
             return NotImplemented
-        return self.data == set(ref(item) for item in other)
+        return self.data == set(map(ref, other))
 
     def symmetric_difference(self, other):
         newset = self.copy()

Lib/distutils/msvc9compiler.py

@@ -255,7 +255,7 @@ def query_vcvarsall(version, arch="x86"):
     """Launch vcvarsall.bat and read the settings from its environment
     """
     vcvarsall = find_vcvarsall(version)
-    interesting = set(("include", "lib", "libpath", "path"))
+    interesting = {"include", "lib", "libpath", "path"}
     result = {}
 
     if vcvarsall is None:

Lib/email/headerregistry.py

@@ -369,8 +369,8 @@ def groups(self):
     @property
     def addresses(self):
         if self._addresses is None:
-            self._addresses = tuple([address for group in self._groups
-                                             for address in group.addresses])
+            self._addresses = tuple(address for group in self._groups
+                                            for address in group.addresses)
         return self._addresses
 
 

Lib/inspect.py

@@ -389,7 +389,7 @@ def classify_class_attrs(cls):
 
     mro = getmro(cls)
     metamro = getmro(type(cls)) # for attributes stored in the metaclass
-    metamro = tuple([cls for cls in metamro if cls not in (type, object)])
+    metamro = tuple(cls for cls in metamro if cls not in (type, object))
     class_bases = (cls,) + mro
     all_bases = class_bases + metamro
     names = dir(cls)

Lib/logging/config.py

@@ -463,7 +463,7 @@ def configure_custom(self, config):
             c = self.resolve(c)
         props = config.pop('.', None)
         # Check for valid identifiers
-        kwargs = dict([(k, config[k]) for k in config if valid_ident(k)])
+        kwargs = dict((k, config[k]) for k in config if valid_ident(k))
         result = c(**kwargs)
         if props:
             for name, value in props.items():
@@ -726,7 +726,7 @@ def configure_handler(self, config):
                 config['address'] = self.as_tuple(config['address'])
             factory = klass
         props = config.pop('.', None)
-        kwargs = dict([(k, config[k]) for k in config if valid_ident(k)])
+        kwargs = dict((k, config[k]) for k in config if valid_ident(k))
         try:
             result = factory(**kwargs)
         except TypeError as te:

Lib/multiprocessing/context.py

@@ -261,7 +261,7 @@ def get_all_start_methods(self):
             else:
                 return ['fork', 'spawn']
 
-DefaultContext.__all__ = list(x for x in dir(DefaultContext) if x[0] != '_')
+DefaultContext.__all__ = [x for x in dir(DefaultContext) if x[0] != '_']
 
 #
 # Context types for fixed start method

Lib/multiprocessing/forkserver.py

@@ -98,8 +98,7 @@ def ensure_running(self):
             if self._preload_modules:
                 desired_keys = {'main_path', 'sys_path'}
                 data = spawn.get_preparation_data('ignore')
-                data = dict((x,y) for (x,y) in data.items()
-                            if x in desired_keys)
+                data = {x: y for x, y in data.items() if x in desired_keys}
             else:
                 data = {}
 

Lib/multiprocessing/sharedctypes.py

@@ -115,7 +115,7 @@ def synchronized(obj, lock=None, ctx=None):
             scls = class_cache[cls]
         except KeyError:
             names = [field[0] for field in cls._fields_]
-            d = dict((name, make_property(name)) for name in names)
+            d = {name: make_property(name) for name in names}
             classname = 'Synchronized' + cls.__name__
             scls = class_cache[cls] = type(classname, (SynchronizedBase,), d)
         return scls(obj, lock, ctx)

Lib/pathlib.py

@@ -114,10 +114,7 @@ class _WindowsFlavour(_Flavour):
 
     is_supported = (os.name == 'nt')
 
-    drive_letters = (
-        set(chr(x) for x in range(ord('a'), ord('z') + 1)) |
-        set(chr(x) for x in range(ord('A'), ord('Z') + 1))
-    )
+    drive_letters = set('abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ')
     ext_namespace_prefix = '\\\\?\\'
 
     reserved_names = (

Lib/pstats.py

@@ -500,8 +500,7 @@ def add_callers(target, source):
         if func in new_callers:
             if isinstance(caller, tuple):
                 # format used by cProfile
-                new_callers[func] = tuple([i[0] + i[1] for i in
-                                           zip(caller, new_callers[func])])
+                new_callers[func] = tuple(i[0] + i[1] for i in zip(caller, new_callers[func]))
             else:
                 # format used by profile
                 new_callers[func] += caller