[util] add 're' helper

gallery_dl/util.py

@@ -32,6 +32,19 @@ try:
 except AttributeError:
     re_compile = re.sre_compile.compile
 
+CACHE_PATTERN = {}
+
+
+def re(pattern):
+    """Compile a regular expression pattern"""
+    try:
+        return CACHE_PATTERN[pattern]
+    except KeyError:
+        pass
+
+    p = CACHE_PATTERN[pattern] = re_compile(pattern)
+    return p
+
 
 def bencode(num, alphabet="0123456789"):
     """Encode an integer into a base-N encoded string"""
@@ -360,9 +373,8 @@ Response Headers
 
             set_cookie = res_headers.get("Set-Cookie")
             if set_cookie:
-                res_headers["Set-Cookie"] = re.sub(
-                    r"(^|, )([^ =]+)=[^,;]*", r"\1\2=***", set_cookie,
-                )
+                res_headers["Set-Cookie"] = re(r"(^|, )([^ =]+)=[^,;]*").sub(
+                    r"\1\2=***", set_cookie)
 
         fmt_nv = "{}: {}".format
 

test/test_util.py

@@ -12,6 +12,7 @@ import sys
 import unittest
 
 import io
+import re
 import time
 import random
 import string
@@ -974,6 +975,25 @@ value = 123
         self.assertEqual(response.headers.get("foo"), None)
         self.assertEqual(response.links.get("next"), None)
 
+    def test_re(self):
+        Pattern = type(re.compile(""))
+
+        p1 = util.re_compile("foo")
+        p2 = util.re("foo")
+        p3 = util.re("foo")
+
+        self.assertIsInstance(p1, Pattern)
+        self.assertIsInstance(p2, Pattern)
+        self.assertIsInstance(p3, Pattern)
+
+        self.assertIsNot(p1, p2)
+        self.assertIs(p2, p3)
+
+        if sys.hexversion >= 0x3060000:
+            self.assertEqual(p1, p2)
+        else:
+            self.assertEqual(repr(p1), repr(p2))
+
 
 class TestExtractor():
     category = "test_category"