style: use walrus for regexing

Author: nedbat

ci/parse_relnotes.py

@@ -44,9 +44,7 @@ def parse_md(lines):
     buffer = TextChunkBuffer()
 
     for line in lines:
-        header_match = re.search(r"^(#+) (.+)$", line)
-        is_header = bool(header_match)
-        if is_header:
+        if header_match := re.search(r"^(#+) (.+)$", line):
             yield from buffer.flush()
             hashes, text = header_match.groups()
             yield (f"h{len(hashes)}", text)
@@ -80,8 +78,7 @@ def sections(parsed_data):
 
 def refind(regex, text):
     """Find a regex in some text, and return the matched text, or None."""
-    m = re.search(regex, text)
-    if m:
+    if m := re.search(regex, text):
         return m.group()
     else:
         return None

coverage/files.py

@@ -300,8 +300,7 @@ def match(self, fpath: str) -> bool:
 
 def sep(s: str) -> str:
     """Find the path separator used in this string, or os.sep if none."""
-    sep_match = re.search(r"[\\/]", s)
-    if sep_match:
+    if sep_match := re.search(r"[\\/]", s):
         the_sep = sep_match[0]
     else:
         the_sep = os.sep
@@ -337,8 +336,7 @@ def _glob_to_regex(pattern: str) -> str:
     pos = 0
     while pos < len(pattern):
         for rx, sub in G2RX_TOKENS:                     # pragma: always breaks
-            m = rx.match(pattern, pos=pos)
-            if m:
+            if m := rx.match(pattern, pos=pos):
                 if sub is None:
                     raise ConfigError(f"File pattern can't include {m[0]!r}")
                 path_rx.append(m.expand(sub))
@@ -469,8 +467,7 @@ def map(self, path: str, exists:Callable[[str], bool] = source_exists) -> str:
             self.pprinted = True
 
         for original_pattern, regex, result in self.aliases:
-            m = regex.match(path)
-            if m:
+            if m := regex.match(path):
                 new = path.replace(m[0], result)
                 new = new.replace(sep(path), sep(result))
                 if not self.relative:

lab/parser.py

@@ -61,8 +61,7 @@ def one_file(self, options, filename):
         # `filename` can have a line number suffix. In that case, extract those
         # lines, dedent them, and use that.  This is for trying test cases
         # embedded in the test files.
-        match = re.search(r"^(.*):(\d+)-(\d+)$", filename)
-        if match:
+        if match := re.search(r"^(.*):(\d+)-(\d+)$", filename):
             filename, start, end = match.groups()
             start, end = int(start), int(end)
         else: