Download all files from FTP in Python

Overview

FTP remains common on legacy hosts. Python's ftplib in the standard library can list and retrieve files without extra dependencies.

Mirror remote folder structure locally for backups or migrations.

Implementation

Connect with FTP(host, user, passwd), cwd into each directory, nlst() for entries, and retrbinary('RETR ' + name, file.write) for files. Recurse into subdirectories when MLSD or LIST indicates directories.

Use passive mode if active fails behind NAT: ftp.set_pasv(True).

When implementing guidance from Download all files from FTP in Python, start in a controlled environment that mirrors production versions of operating systems, runtimes, and network policies. Capture a baseline before changes: export configs, snapshot VMs, or tag releases in source control so rollback stays straightforward if behavior regresses.

Document prerequisites, expected outcomes, and verification steps in a short runbook. Automated checks—smoke tests, health endpoints, or query validations—catch regressions early when platforms receive patches. Security belongs in every workflow: apply least privilege, rotate secrets, and review audit logs after deployment.

If results differ across machines, compare environment variables, permission models, time zones, and regional settings. Intermittent issues often trace to caching layers, stale DNS, or duplicated services bound to the same port.

Example

from ftplib import FTP
from pathlib import Path

def download_tree(ftp, remote, local):
    Path(local).mkdir(parents=True, exist_ok=True)
    for name in ftp.nlst(remote):
        local_path = Path(local) / Path(name).name
        try:
            with open(local_path, 'wb') as f:
                ftp.retrbinary(f'RETR {name}', f.write)
        except error_perm:
            download_tree(ftp, name, local_path)

Tips

• Prefer SFTP (paramiko) for encrypted transfers.
• Handle permission errors on LIST vs NLST.
• Resume large files with REST if server supports it.
• Never embed passwords; use environment variables.

• Re-verify after reboots, certificate renewals, or failover exercises.
• Align monitoring and alerts with the failure modes described in this guide.
• Keep vendor documentation links handy for breaking changes between versions.
• Pair automation with a manual spot check during initial production rollout.