Python File Processing Lab

import csv
import sys
from pathlib import Path


def make_report(source, destination):
    if source.resolve() == destination.resolve():
        raise ValueError("Input and output must be different files")
    fields = ["name", "server", "status"]
    count = 0
    created = False
    try:
        with source.open(encoding="utf-8", newline="") as src:
            reader = csv.DictReader(src, strict=True)
            if reader.fieldnames != fields:
                raise ValueError("Expected headers: name,server,status")
            with destination.open("x", encoding="utf-8", newline="") as dst:
                created = True
                writer = csv.DictWriter(dst, fieldnames=fields)
                writer.writeheader()
                for row in reader:
                    if None in row or any(row[key] is None for key in fields):
                        raise ValueError("Unexpected number of fields")
                    if row["status"] == "critical":
                        writer.writerow(row)
                        count += 1
    except (OSError, ValueError, csv.Error, UnicodeError):
        if created:
            destination.unlink(missing_ok=True)
        raise
    return count


def main():
    try:
        count = make_report(Path("servers.csv"), Path("critical-servers.csv"))
    except (OSError, ValueError, csv.Error, UnicodeError) as error:
        print(f"Report failed: {error}", file=sys.stderr)
        return 1
    print(f"Found {count} critical servers.")
    return 0


if __name__ == "__main__":
    raise SystemExit(main())