Make instantiation fast when using the default alphabet and blocklist

assets/filter_blocklist.py

@@ -0,0 +1,99 @@
+import pathlib
+import sys
+from typing import Set, Tuple
+
+
+repo_root = pathlib.Path(__file__).parent.parent
+this_file = pathlib.Path(__file__).relative_to(repo_root)
+constants_path = repo_root / "sqids/constants.py"
+import sqids.constants  # noqa
+
+
+DIGITS = set("0123456789")
+
+
+def filter_blocklist() -> Tuple[Set[str], Set[str], Set[str]]:
+    """Pre-filter the blocklist and update the constants file."""
+
+    exact_match = set()
+    match_at_ends = set()
+    match_anywhere = set()
+
+    for word in sqids.constants.DEFAULT_BLOCKLIST:
+        if len(word) == 3:
+            exact_match.add(word)
+        elif set(word) & DIGITS:
+            match_at_ends.add(word)
+        else:
+            match_anywhere.add(word)
+
+    return exact_match, match_at_ends, match_anywhere
+
+
+def generate_new_constants_file(
+    exact_match: Set[str],
+    match_at_ends: Set[str],
+    match_anywhere: Set[str],
+) -> str:
+    """Generate the text of a new constants file."""
+
+    lines = [
+        f'DEFAULT_ALPHABET = "{sqids.constants.DEFAULT_ALPHABET}"',
+        f"DEFAULT_MIN_LENGTH = {sqids.constants.DEFAULT_MIN_LENGTH}",
+        "",
+        "# =======",
+        "#  NOTE",
+        "# =======",
+        "#",
+        f"# When updating the blocklist, run {this_file} to pre-filter constants.",
+        "# This is critical for performance.",
+        "#",
+        "",
+        "DEFAULT_BLOCKLIST = [",
+    ]
+    # Output a sorted blocklist.
+    for word in sorted(sqids.constants.DEFAULT_BLOCKLIST):
+        lines.append(f'    "{word}",')
+    lines.append("]")
+
+    # Output exact-match blocklist words.
+    lines.append("")
+    lines.append("_exact_match = {")
+    for word in sorted(exact_match):
+        lines.append(f'    "{word}",')
+    lines.append("}")
+
+    # Output match-at-ends blocklist words.
+    lines.append("")
+    lines.append("_match_at_ends = (")
+    for word in sorted(match_at_ends):
+        lines.append(f'    "{word}",')
+    lines.append(")")
+
+    # Output match-anywhere blocklist words.
+    lines.append("")
+    lines.append("_match_anywhere = {")
+    for word in sorted(match_anywhere):
+        lines.append(f'    "{word}",')
+    lines.append("}")
+
+    return "\n".join(lines).rstrip() + "\n"  # Include a trailing newline.
+
+
+def main() -> int:
+    text = constants_path.read_text()
+
+    exact_match, match_at_ends, match_anywhere = filter_blocklist()
+    new_text = generate_new_constants_file(exact_match, match_at_ends, match_anywhere)
+
+    if text == new_text:
+        print("No changes necessary")
+        return 0
+
+    print(f"Updating {constants_path.relative_to(repo_root)}")
+    constants_path.write_text(new_text, newline="\n", encoding="utf-8")
+    return 1
+
+
+if __name__ == "__main__":
+    sys.exit(main())