gh-130167: Improve speed of _pydecimal._all_zeros and _pydecimal._exact_half by replacing re

Lib/_pydecimal.py

@@ -6076,8 +6076,29 @@ def _convert_for_comparison(self, other, equality_op=False):
     \Z
 """, re.VERBOSE | re.IGNORECASE).match
 
-_all_zeros = re.compile('0*$').match
-_exact_half = re.compile('50*$').match
+# Checks for regex 0*$
+def _all_zeros(d_int, prec=0):
+    i = prec
+    len_d = len(d_int)
+
+    while i < len_d:
+        if d_int[i] != '0':
+            return False
+        i += 1
+    return True
+
+# Checks for regex 50*$ 
+def _exact_half(d_int, prec=0):
+    len_d = len(d_int)
+    i = prec + 1
+
+    if len_d >= i and d_int[prec] == '5':
+        while i < len_d:
+            if d_int[i] != '0':
+                return False
+            i += 1
+        return True
+    return False
 
 ##### PEP3101 support functions ##############################################
 # The functions in this section have little to do with the Decimal

Misc/NEWS.d/next/Library/2025-04-04-04-07-16.gh-issue-130167.XigAlq.rst

@@ -0,0 +1,2 @@
+Improved performance of :func:`_pydecimal._all_zeros` by an average of
+~1.7x and :func:`_pydecimal._exact_half` by ~1.38x. Patch by Marius Juston