title: python download images are not saved to the correct directory
body: <p>When i use python 2.7 to download images from a website, the code as follows:</p>
  
  <pre><code>pic = requests.get(src[0])
  f = open("pic\\"+str(i) + '.jpg', "wb")
  f.write(pic.content)
  f.close()
  i += 1
  </code></pre>
  
  <p>I want to save the picture into pic directory, but I find that images is saved in the same directory with the name like <code>pic\1.jpg</code>. Is this a bug?</p>
  
  <p>In Windows, it's right, but on Ubuntu, it's an error!</p>