How to Decrypt a GPG File with a Passphrase in Python

import subprocess
import tempfile
from pathlib import Path


def decrypt_gpg_file(input_file: str, passphrase: str) -> str:
    """Decrypt a GPG file using a passphrase and return the plaintext."""
    result = subprocess.run(
        ["gpg", "--batch", "--yes", "--passphrase", passphrase, "--decrypt", input_file],
        capture_output=True,
        text=True,
        check=False,
    )
    if result.returncode != 0:
        raise RuntimeError(f"GPG decryption failed: {result.stderr.strip()}")
    return result.stdout


if __name__ == "__main__":
    # Create a mock encrypted file for demonstration
    with tempfile.TemporaryDirectory() as tmpdir:
        plaintext_path = Path(tmpdir) / "secret.txt"
        encrypted_path = Path(tmpdir) / "secret.txt.gpg"

        plaintext_path.write_text("Hello, GPG world!", encoding="utf-8")
        subprocess.run(
            ["gpg", "--batch", "--yes", "--passphrase", "demo-pass", "-c", "-o", str(encrypted_path), str(plaintext_path)],
            check=True,
            capture_output=True,
        )

        decrypted = decrypt_gpg_file(str(encrypted_path), "demo-pass")
        print(decrypted)