Question

I’m scripting an install script in python.

How do I download file from ftp in python?

Operating system — Windows XP – if that makes a difference.

Answer 1

Here’s a code snippet I’m currently using.

import mimetypes
import os
import urllib2
import urlparse

def filename_from_url(url):
    return os.path.basename(urlparse.urlsplit(url)[2])

def download_file(url):
    """Create an urllib2 request and return the request plus some useful info"""
    name = filename_from_url(url)
    r = urllib2.urlopen(urllib2.Request(url))
    info = r.info()
    if 'Content-Disposition' in info:
        # If the response has Content-Disposition, we take filename from it
        name = info['Content-Disposition'].split('filename=')[1]
        if name[0] == '"' or name[0] == "'":
            name = name[1:-1]
    elif r.geturl() != url:
        # if we were redirected, take the filename from the final url
        name = filename_from_url(r.geturl())
    content_type = None
    if 'Content-Type' in info:
        content_type = info['Content-Type'].split(';')[0]
    # Try to guess missing info
    if not name and not content_type:
        name = 'unknown'
    elif not name:
        name = 'unknown' + mimetypes.guess_extension(content_type) or ''
    elif not content_type:
        content_type = mimetypes.guess_type(name)[0]
    return r, name, content_type

Usage:

req, filename, content_type = download_file('http://some.url')

Then you can use req as a file-like object and e.g. use shutil.copyfileobj() to copy the file contents into a local file. If the MIME type doesn’t matter simply remove that part of the code.

Since you seem to be lazy, here’s code downloading the file directly to a local file:

import shutil
def download_file_locally(url, dest):
    req, filename, content_type = download_file(url)        
    if dest.endswith('/'):
        dest = os.path.join(dest, filename)
    with open(dest, 'wb') as f:
        shutil.copyfileobj(req, f)
    req.close()

This method is smart enough to use the filename sent by the server if you specify a path ending with a slash, otherwise it uses the destination you specified.