Python: Check if uploaded file is jpg

Question

How can I check if a file uploaded by a user is a real jpg file in Python (Google App Engine)?

This is how far I got by now:

Script receives image via HTML F

Answer 1

No need to use and install the PIL lybrary for this, there is the imghdr standard module exactly fited for this sort of usage.

See http://docs.python.org/library/imghdr.html

import imghdr

image_type = imghdr.what(filename)
if not image_type:
    print "error"
else:
    print image_type

As you have an image from a stream you may use the stream option probably like this :

image_type = imghdr.what(filename, incomming_image)

---

Actualy this works for me in Pylons (even if i have not finished everything) : in the Mako template :

${h.form(h.url_for(action="save_image"), multipart=True)}
Upload file: ${h.file("upload_file")} 

${h.submit("Submit", "Submit")}
${h.end_form()}

in the upload controler :

def save_image(self):
    upload_file = request.POST["upload_file"]
    image_type = imghdr.what(upload_file.filename, upload_file.value)
    if not image_type:
        return "error"
    else:
        return image_type