CODEWITHSUNDEEP
pythongoogle-app-enginepdf
David Freeman
David Freeman

Reputation: 125

App Engine - download files from Cloud Storage

I am using Python 2.7 and Reportlab to create .pdf files for display/print in my app engine system. I am using ndb.Model to store the data if that matters.

I am able to produce the equivalent of a bank statement for a single client on-line. That is; the user clicks the on-screen 'pdf' button and the .pdf statement appears on screen in a new tab, exactly as it should.

I am using the following code to save .pdf files to Google Cloud Storage successfully

buffer = StringIO.StringIO()
self.p = canvas.Canvas(buffer, pagesize=portrait(A4))
self.p.setLineWidth(0.5)

try:

    # create .pdf of .csv data here

finally:
    self.p.save()
    pdfout = buffer.getvalue()
    buffer.close()

    filename = getgcsbucket() + '/InvestorStatement.pdf'  
    write_retry_params = gcs.RetryParams(backoff_factor=1.1)

    try:
        gcs_file = gcs.open(filename,
                            'w',
                            content_type='application/pdf',
                            retry_params=write_retry_params)
        gcs_file.write(pdfout)
    except:
        logging.error(traceback.format_exc())
    finally:
        gcs_file.close()

I am using the following code to create a list of all files for display on-screen, it shows all the files stored above.

allfiles = []

bucket_name = getgcsbucket()

rfiles = gcs.listbucket(bucket_name)
for rfile in rfiles:
    allfiles.append(rfile.filename)

return allfiles

My screen (html) shows rows of ([Delete] and Filename). When the user clicks the [Delete] button, the following delete code snippet works (filename is /bucket/filename, complete)

filename = self.request.get('filename')
try:
    gcs.delete(filename)
except gcs.NotFoundError:
    pass

My question - given I have a list of files on-screen, I want the user to click on the filename and for that file to be downloaded to the user's computer. In Google's Chrome Browser, this would result in the file being downloaded, with it's name displayed on the bottom left of the screen.

One other point, the above example is for .pdf files. I will also have to show .csv files in the list and would like them to be downloaded as well. I only want the files to be downloaded, no display is required.

So, I would like a snippet like ...

filename = self.request.get('filename')
try:
    gcs.downloadtousercomputer(filename) ???
except gcs.NotFoundError:
    pass

I think I have tried everything I can find both here and elsewhere. Sorry I have been so long-winded. Any hints for me?

Upvotes: 2

Views: 1692

Answers (2)

J0nh1dd3n
J0nh1dd3n

Reputation: 171

One solution you can try is to read the file from the bucket and print the content as the response with the correct header:

import cloudstorage
...
def read_file(self, filename):        
    bucket_name = "/your_bucket_name"        
    file = bucket_name + '/' + filename        
    with cloudstorage.open(file) as cloudstorage_file: 
        self.response.headers["Content-Disposition"] = str('attachment;filename=' + filename)            
        contents = cloudstorage_file.read()         
        cloudstorage_file.close()            
        self.response.write(contents)

Here filename could be something you are sending as GET parameter and needs to be a file that exist on your bucket or you will raise an exception.

[1] Here you will find a sample.

[1]https://cloud.google.com/appengine/docs/standard/python/googlecloudstorageclient/read-write-to-cloud-storage

Upvotes: 0

minou
minou

Reputation: 16553

To download a file instead of showing it in the browser, you need to add a header to your response:

self.response.headers["Content-Disposition"] = 'attachment; filename="%s"' % filename

You can specify the filename as shown above and it works for any file type.

Upvotes: 1

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