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File UploadsΒΆ

There are two parts necessary for handling file uploads. The first is to make sure you have a form that’s been setup correctly to accept files. This means adding enctype attribute to your form element with the value of multipart/form-data. A very simple example would be a form that accepts an mp3 file. Notice we’ve setup the form as previously explained and also added an input element of the file type.

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<form action="/store_mp3_view" method="post" accept-charset="utf-8"
      enctype="multipart/form-data">

    <label for="mp3">Mp3</label>
    <input id="mp3" name="mp3" type="file" value="" />

    <input type="submit" value="submit" />
</form>

The second part is handling the file upload in your view callable (above, assumed to answer on /store_mp3_view). The uploaded file is added to the request object as a cgi.FieldStorage object accessible through the request.POST multidict. The two properties we’re interested in are the file and filename and we’ll use those to write the file to disk:

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import os
import uuid
from pyramid.response import Response

def store_mp3_view(request):
    # ``filename`` contains the name of the file in string format.
    #
    # WARNING: this example does not deal with the fact that IE sends an
    # absolute file *path* as the filename.  This example is naive; it
    # trusts user input.

    filename = request.POST['mp3'].filename

    # ``input_file`` contains the actual file data which needs to be
    # stored somewhere.

    input_file = request.POST['mp3'].file

    # Note that we are generating our own filename instead of trusting
    # the incoming filename since that might result in insecure paths.
    # Please note that in a real application you would not use /tmp,
    # and if you write to an untrusted location you will need to do
    # some extra work to prevent symlink attacks.

    file_path = os.path.join('/tmp', '%s.mp3' % uuid.uuid4())

    # We first write to a temporary file to prevent incomplete files from
    # being used.

    temp_file_path = file_path + '~'
    output_file = open(temp_file_path, 'wb')

    # Finally write the data to a temporary file
    input_file.seek(0)
    while True:
        data = input_file.read(2<<16)
        if not data:
            break
        output_file.write(data)

    # If your data is really critical you may want to force it to disk first
    # using output_file.flush(); os.fsync(output_file.fileno())

    output_file.close()

    # Now that we know the file has been fully saved to disk move it into place.

    os.rename(temp_file_path, file_path)

    return Response('OK')

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