chore: minor cleanups and perf tweaks from code review (#2910)

* chore: minor cleanups and perf tweaks from code review

- util/file.py, util/python_build_standalone.py: use hashlib.file_digest
  for streaming SHA-256 verification instead of loading whole archives
  into memory with read_bytes()
- logger.py: convert colors/symbols properties to functools.cached_property
  so the Colors/Symbols objects are constructed only once per Logger instance
- platforms/windows.py: remove redundant .strip() on where_pip (already
  stripped at assignment)
- util/python_build_standalone.py: remove unreachable python_base_dir.exists()
  guard (callers always pass a fresh temp subdirectory)
- util/file.py: add comment explaining the getattr shim for
  tar_.extraction_filter and when it can be removed

Assisted-by: ClaudeCode:claude-fable-5

* revert: restore assertion to check python_base_dir existence

cibuildwheel/logger.py

@@ -375,11 +375,11 @@ class Logger:
         out.write("\n")
         return out.getvalue()
 
-    @property
+    @functools.cached_property
     def colors(self) -> Colors:
         return Colors(enabled=self.colors_enabled)
 
-    @property
+    @functools.cached_property
     def symbols(self) -> Symbols:
         return Symbols(unicode=self.unicode_enabled)
 

cibuildwheel/platforms/windows.py

@@ -348,7 +348,7 @@ def setup_python(
         assert (venv_path / "Scripts" / "pip.exe").exists()
         where_pip = call("where", "pip", env=env, capture_stdout=True).splitlines()[0].strip()
         print(where_pip)
-        if where_pip.strip() != str(venv_path / "Scripts" / "pip.exe"):
+        if where_pip != str(venv_path / "Scripts" / "pip.exe"):
             msg = "pip available on PATH doesn't match our installed instance. If you have modified PATH, ensure that you don't overwrite cibuildwheel's entry or insert pip above it."
             raise errors.FatalError(msg)
         call("pip", "--version", env=env)

cibuildwheel/util/file.py

@@ -99,7 +99,8 @@ def download(url: str, dest: Path, *, sha256: str | None = None) -> None:
             time.sleep(3)
 
     if sha256:
-        computed = hashlib.sha256(dest.read_bytes()).hexdigest()
+        with dest.open("rb") as f:
+            computed = hashlib.file_digest(f, "sha256").hexdigest()
         if computed != sha256:
             dest.unlink(missing_ok=True)
             msg = f"SHA256 mismatch for {url}: expected {sha256!r}, got {computed!r}"
@@ -130,6 +131,8 @@ def extract_tar(tar_src: Path, dest: Path) -> None:
     See: https://docs.python.org/3/library/tarfile.html#tarfile.tar_filter for filter details
     """
     with tarfile.open(tar_src) as tar_:
+        # getattr shim needed while Python 3.11.0-3.11.3 are supported;
+        # once the minimum is 3.11.4+/3.12, replace with: tar_.extractall(dest, filter="tar")
         tar_.extraction_filter = getattr(tarfile, "tar_filter", (lambda member, _: member))
         tar_.extractall(dest)
 

cibuildwheel/util/python_build_standalone.py

@@ -154,7 +154,8 @@ def _download_or_get_from_cache(
         asset_cache_path = cache_dir / asset_filename
         if asset_cache_path.is_file():
             if sha256:
-                computed = hashlib.sha256(asset_cache_path.read_bytes()).hexdigest()
+                with asset_cache_path.open("rb") as f:
+                    computed = hashlib.file_digest(f, "sha256").hexdigest()
                 if computed != sha256:
                     print(
                         f"Cached python_build_standalone SHA256 mismatch for {asset_cache_path}; redownloading."
@@ -229,9 +230,7 @@ def create_python_build_standalone_environment(
     )
 
     python_base_dir = temp_dir / "pbs"
-    if python_base_dir.exists():
+    assert not python_base_dir.exists()
-        msg = f"python-build-standalone directory already exists: {python_base_dir}"
-        raise PythonBuildStandaloneError(msg)
     extract_tar(archive_path, python_base_dir)
 
     return _find_python_executable(python_base_dir)