Fix Python code errors in playground HTML files

- index-playground.html: Replace .to_list() with .tolist() for numpy
  array results from isin(), argsort(), isna(), notna()
- ewm.html: Add raw=True to ewm().apply() for pandas 3.0 compatibility
- nlargest.html: Replace nlargest/nsmallest on string Series with
  sort_values().head() which works in pandas

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

Co-authored-by: mrjf <180956+mrjf@users.noreply.github.com>

Author: Copilot

playground/ewm.html

@@ -548,7 +548,7 @@ <h2>9 · Custom apply</h2>
 
 # EWM weighted sum (equivalent to unadjusted numerator)
 # Note: pandas ewm.apply() does not pass weights; custom logic needed
-ewm_weighted_sum = s.ewm(alpha=0.5).apply(lambda vals: sum(vals))
+ewm_weighted_sum = s.ewm(alpha=0.5).apply(lambda vals: sum(vals), raw=True)
 print("weighted sum:", list(ewm_weighted_sum))</textarea>
       <div class="playground-output">Click ▶ Run to execute</div>
       <div class="playground-hint">Ctrl+Enter to run · Tab to indent</div>

playground/index-playground.html

@@ -318,7 +318,7 @@ <h2>Label Look-up</h2>
 print("get_loc('b'):", idx.get_loc("b"))     # unique → single int
 print("get_loc('a'):", idx.get_loc("a"))     # duplicated → boolean mask
 print("contains 'c':", "c" in idx)
-print("isin(['a', 'c']):", idx.isin(["a", "c"]).to_list())</textarea>
+print("isin(['a', 'c']):", idx.isin(["a", "c"]).tolist())</textarea>
       <div class="playground-output">Click ▶ Run to execute</div>
       <div class="playground-hint">Ctrl+Enter to run · Tab to indent</div>
     </div>
@@ -386,7 +386,7 @@ <h2>Sorting &amp; Aggregation</h2>
 idx = pd.Index([30, 10, 20])
 
 print("sort_values:", idx.sort_values().to_list())
-print("argsort:   ", idx.argsort().to_list())
+print("argsort:   ", idx.argsort().tolist())
 print("min:", idx.min())
 print("max:", idx.max())
 print("argmin:", idx.argmin())
@@ -456,8 +456,8 @@ <h2>Missing Values</h2>
 
 idx = pd.Index([1, None, 3])
 
-print("isna: ", idx.isna().to_list())
-print("notna:", idx.notna().to_list())
+print("isna: ", idx.isna().tolist())
+print("notna:", idx.notna().tolist())
 print("dropna:", idx.dropna().to_list())
 print("fillna(0):", idx.fillna(0).to_list())</textarea>
       <div class="playground-output">Click ▶ Run to execute</div>

playground/nlargest.html

@@ -531,8 +531,8 @@ <h2>8 · Edge cases</h2>
 
 # string values — lexicographic order
 words = pd.Series(["banana", "apple", "cherry"])
-print("largest strings:", words.nlargest(2).tolist())
-print("smallest strings:", words.nsmallest(2).tolist())</textarea>
+print("largest strings:", words.sort_values(ascending=False).head(2).tolist())
+print("smallest strings:", words.sort_values().head(2).tolist())</textarea>
       <div class="playground-output">Click ▶ Run to execute</div>
       <div class="playground-hint">Ctrl+Enter to run · Tab to indent</div>
     </div>

scripts/validate-python-examples.py

@@ -0,0 +1,145 @@
+#!/usr/bin/env python3
+"""
+Validate Python/pandas examples from playground HTML pages.
+
+Extracts all <textarea class="playground-python"> blocks from playground HTML
+files, runs each one with Python/pandas, and reports any failures.
+
+Usage:
+    python scripts/validate-python-examples.py [playground_dir]
+
+Exit code 0 if all examples pass, 1 if any fail.
+"""
+
+import html
+import os
+import re
+import subprocess
+import sys
+import tempfile
+import time
+
+
+def extract_python_blocks(html_file: str) -> list[tuple[str, str]]:
+    """Extract Python code blocks from a playground HTML file.
+
+    Returns a list of (section_label, code) tuples.
+    """
+    with open(html_file, "r", encoding="utf-8") as f:
+        content = f.read()
+
+    blocks: list[tuple[str, str]] = []
+
+    # Find all playground-python textareas
+    pattern = re.compile(
+        r'<textarea\s+class="playground-python"[^>]*>(.*?)</textarea>',
+        re.DOTALL,
+    )
+
+    # Also find section headings to label blocks
+    section_pattern = re.compile(r"<h2>(.*?)</h2>", re.DOTALL)
+    sections = section_pattern.findall(content)
+
+    for i, match in enumerate(pattern.finditer(content)):
+        code = html.unescape(match.group(1))
+        # Try to find the closest preceding section heading
+        label = sections[i] if i < len(sections) else f"block_{i}"
+        # Strip HTML tags from label
+        label = re.sub(r"<[^>]+>", "", label).strip()
+        blocks.append((label, code))
+
+    return blocks
+
+
+def run_python_block(code: str, label: str, html_file: str) -> tuple[bool, str, float]:
+    """Run a Python code block and return (success, output, elapsed_ms)."""
+    with tempfile.NamedTemporaryFile(
+        mode="w", suffix=".py", delete=False, encoding="utf-8"
+    ) as f:
+        f.write(code)
+        tmp_path = f.name
+
+    try:
+        start = time.perf_counter()
+        result = subprocess.run(
+            [sys.executable, tmp_path],
+            capture_output=True,
+            text=True,
+            timeout=30,
+        )
+        elapsed_ms = (time.perf_counter() - start) * 1000
+
+        if result.returncode != 0:
+            return (
+                False,
+                f"STDERR:\n{result.stderr}\nSTDOUT:\n{result.stdout}",
+                elapsed_ms,
+            )
+        return True, result.stdout, elapsed_ms
+    except subprocess.TimeoutExpired:
+        return False, "TIMEOUT (30s)", 0.0
+    finally:
+        os.unlink(tmp_path)
+
+
+def main() -> int:
+    playground_dir = sys.argv[1] if len(sys.argv) > 1 else "playground"
+
+    if not os.path.isdir(playground_dir):
+        print(f"Error: directory '{playground_dir}' not found", file=sys.stderr)
+        return 1
+
+    html_files = sorted(
+        f
+        for f in os.listdir(playground_dir)
+        if f.endswith(".html") and f != "index.html"
+    )
+
+    total = 0
+    passed = 0
+    failed = 0
+    failures: list[str] = []
+
+    for html_file in html_files:
+        filepath = os.path.join(playground_dir, html_file)
+        blocks = extract_python_blocks(filepath)
+
+        if not blocks:
+            continue
+
+        print(f"\n{'='*60}")
+        print(f"  {html_file} ({len(blocks)} Python blocks)")
+        print(f"{'='*60}")
+
+        for i, (label, code) in enumerate(blocks):
+            total += 1
+            success, output, elapsed_ms = run_python_block(
+                code, label, html_file
+            )
+
+            if success:
+                passed += 1
+                print(f"  ✅ [{i+1}] {label} ({elapsed_ms:.1f}ms)")
+            else:
+                failed += 1
+                fail_msg = f"  ❌ [{i+1}] {label} in {html_file}"
+                print(fail_msg)
+                print(f"     {output[:200]}")
+                failures.append(f"{html_file} [{i+1}] {label}")
+
+    print(f"\n{'='*60}")
+    print(f"  Results: {passed}/{total} passed, {failed} failed")
+    print(f"{'='*60}")
+
+    if failures:
+        print("\nFailed examples:")
+        for f in failures:
+            print(f"  - {f}")
+        return 1
+
+    print("\n✅ All Python examples validated successfully!")
+    return 0
+
+
+if __name__ == "__main__":
+    sys.exit(main())