# Python Sample: File Validation Pipeline

```python
from pathlib import Path
import pandas as pd

INPUT_DIR = Path("/data/inbound")
QUARANTINE_DIR = Path("/data/quarantine")
REQUIRED_COLUMNS = {"member_id", "service_date", "amount"}

def validate_file(csv_path: Path) -> tuple[bool, str]:
    frame = pd.read_csv(csv_path)
    missing = REQUIRED_COLUMNS - set(frame.columns.str.lower())
    if missing:
        return False, f"Missing required columns: {sorted(missing)}"
    if frame["amount"].isna().any():
        return False, "Amount column contains null values"
    return True, "Validation passed"

for file_path in INPUT_DIR.glob("*.csv"):
    is_valid, message = validate_file(file_path)
    print(f"{file_path.name}: {message}")
    if not is_valid:
        target = QUARANTINE_DIR / file_path.name
        file_path.replace(target)
```

Use this pattern to:
- Validate schema before ETL load.
- Route failed files to quarantine.
- Produce lightweight validation logs.