Django - Get uploaded file type / mimetype

class MyForm(forms.ModelForm):

    def clean_file(self):
        file = self.cleaned_data['file']
        try:
            if file:
                file_type = file.content_type.split('/')[0]
                print file_type

                if len(file.name.split('.')) == 1:
                    raise forms.ValidationError(_('File type is not supported'))

                if file_type in settings.TASK_UPLOAD_FILE_TYPES:
                    if file._size > settings.TASK_UPLOAD_FILE_MAX_SIZE:
                        raise forms.ValidationError(_('Please keep filesize under %s. Current filesize %s') % (filesizeformat(settings.TASK_UPLOAD_FILE_MAX_SIZE), filesizeformat(file._size)))
                else:
                    raise forms.ValidationError(_('File type is not supported'))
        except:
            pass

        return file

settings.py

TASK_UPLOAD_FILE_TYPES = ['pdf', 'vnd.oasis.opendocument.text','vnd.ms-excel','msword','application',]
TASK_UPLOAD_FILE_MAX_SIZE = "5242880"

You can use PIL or magic to read the few first bytes and get the MIME type that way. I wouldn't trust the content_type since anyone can fake an HTTP header.

Magic solution below. For a PIL implementation you can get an idea from django's get_image_dimensions.

import magic


def get_mime_type(file):
    """
    Get MIME by reading the header of the file
    """
    initial_pos = file.tell()
    file.seek(0)
    mime_type = magic.from_buffer(file.read(2048), mime=True)
    file.seek(initial_pos)
    return mime_type

File is the in-memory uploaded file in the view.