add 'noop()' and 'identity()' functions

gallery_dl/extractor/sankaku.py

@@ -10,7 +10,7 @@
 
 from .booru import BooruExtractor
 from .common import Message
-from .. import text, exception
+from .. import text, util, exception
 from ..cache import cache
 import collections
 
@@ -206,7 +206,7 @@ class SankakuAPI():
 
         self.username, self.password = self.extractor._get_auth_info()
         if not self.username:
-            self.authenticate = lambda: None
+            self.authenticate = util.noop
 
     def pools(self, pool_id):
         params = {"lang": "en"}

gallery_dl/job.py

@@ -638,7 +638,7 @@ class DataJob(Job):
         self.ascii = config.get(("output",), "ascii", ensure_ascii)
 
         private = config.get(("output",), "private")
-        self.filter = (lambda x: x) if private else util.filter_dict
+        self.filter = util.identity if private else util.filter_dict
 
     def run(self):
         sleep = self.extractor.config("sleep-extractor")

gallery_dl/util.py

@@ -81,6 +81,15 @@ def raises(cls):
     return wrap
 
 
+def identity(x):
+    """Returns its argument"""
+    return x
+
+
+def noop():
+    """Does nothing"""
+
+
 def generate_token(size=16):
     """Generate a random token with hexadecimal digits"""
     data = random.getrandbits(size * 8).to_bytes(size, "big")
@@ -804,7 +813,7 @@ class PathFormat():
     @staticmethod
     def _build_cleanfunc(chars, repl):
         if not chars:
-            return lambda x: x
+            return identity
         elif isinstance(chars, dict):
             def func(x, table=str.maketrans(chars)):
                 return x.translate(table)

test/test_util.py

@@ -484,6 +484,13 @@ class TestOther(unittest.TestCase):
         with self.assertRaises(ValueError):
             func(3)
 
+    def test_identity(self):
+        for value in (123, "foo", [1, 2, 3], (1, 2, 3), {1: 2}, None):
+            self.assertIs(util.identity(value), value)
+
+    def test_noop(self):
+        self.assertEqual(util.noop(), None)
+
     def test_generate_token(self):
         tokens = set()
         for _ in range(100):