python save image from url

I got a problem when I am using python to save an image from url either by urllib2 request or urllib.urlretrieve. That is the url of the image is valid. I could download it manually using the explorer. However, when I use python to download the image, the file cannot be opened. I use Mac OS preview to view the image. Thank you!

UPDATE:

The code is as follow

def downloadImage(self):
    request = urllib2.Request(self.url)
    pic = urllib2.urlopen(request)
    print "downloading: " + self.url
    print self.fileName
    filePath = localSaveRoot + self.catalog  + self.fileName + Picture.postfix
    # urllib.urlretrieve(self.url, filePath)
    with open(filePath, 'wb') as localFile:
        localFile.write(pic.read())

The image URL that I want to download is http://site.meishij.net/r/58/25/3568808/a3568808_142682562777944.jpg

This URL is valid and I can save it through the browser but the python code would download a file that cannot be opened. The Preview says "It may be damaged or use a file format that Preview doesn't recognize." I compare the image that I download by Python and the one that I download manually through the browser. The size of the former one is several byte smaller. So it seems that the file is uncompleted, but I don't know why python cannot completely download it.

Solution

A sample code that works for me on Windows:

import requests

with open('pic1.jpg', 'wb') as handle:
    response = requests.get(pic_url, stream=True)

    if not response.ok:
        print(response)

    for block in response.iter_content(1024):
        if not block:
            break

        handle.write(block)