Upload Download files

Using multiple tables in the same page as you know requires explicitly adding form name when you accept it

suppose a situation in which you need to make multiple upload forms in the same page may be for users to upload their cvs

Now you’ve 3 problems :

• How could you add multiple forms in the same page and in the same time make them work ?
• How to upload the files (cvs)
• How to download them

def jobs():
        ...............................................
        ...............................................
        jobs = db(...).select(...)
        for job in jobs:
            # I'll use the same name for form name as well as the field
            formname = "upload_f_%s"%job.id
            form = FORM(INPUT(_type="file",_name=formname,
                          requires=[IS_NOT_EMPTY(),
                                    IS_LENGTH(1048576, 1024, error_message=CustomMessages.UPLOAD_CV_SIZE)
                                   ]
                          ),
                    INPUT(_type='submit'))
        
            if form.accepts(request.vars, formname=formname):
                stream=eval('form.vars.%s.file'%formname)
                filename= eval('form.vars.%s.filename'%formname)        
                file_id = db.cvs.insert(cv=db.cvs.cv.store(stream,filename=filename),
                                    job_title=job.title,
                                    job_id=job.id)
            
                # add permissions for that file    

                # do other stuff       

As you see , I made a form with a field of type ‘file’ and form name is variable based on the job_id , C.Vs are going to be uploaded
this helps making multiple forms per page and in the same time every form has a unique name that will be used when accepting the form .

Now as you may have guessed the form containing a ‘file’ field will have (when being accepted) :

form.vars.field_name.file  -> get the reference to the file
form.vars.field_name.filename  -> get the file name

Now you can easily do something like:

stream=form.vars.field_name.file
filename= form.vars.field_name.filename

Now you can store your file name into the database

db.cvs.insert(cv=db.cvs.cv.store(stream,filename=filename),
                                    job_title=job.title,
                                    job_id=job.id)

see the :

db.table_name.field_of_type_upload.store()

Congratulations !!! you’ve uploaded your files

Now for downloading files you can do :

def download_cv():
    file_id = request.args(0)
    import cStringIO 
    import contenttype as c
    s=cStringIO.StringIO() 
    
    (filename,file) = db.cvs.cv.retrieve(db.cvs[file_id].cv)
    s.write(file.read())  
    response.headers['Content-Type'] = c.contenttype(filename)
    response.headers['Content-Disposition'] = \
                "attachment; filename=%s" % filename  
    return s.getvalue()

Now you can make another function that list all cvs available with a link for downloading them as follows:

def list_Cvs():
    cvs = db(db.cvs.id>0).select(db.cvs.cv) # db.cvs.cv is of type 'upload'
    urls = [A('Download', _href=URL(r=request,\
                                               c='files',
                                               f='download_cv', args=[row.id]
                 )) for row in cvs]
    return urls

what is the benefit of writing my own download function ?
This enables you to write your own authorization logic before allowing a user to download a file

---

Now what if I just don’t want to write my own download function and use web2py facilities for that matter ?

You can use response.stream(), or response.download() functions.

What is difference between them?

In fact response.stream is the main download function that takes care of streaming files.
response.download() calls response.stream() to do the streaming stuff.

response.download() has its arguments as request, db and is used for downloading files by their names, while the name is the name of the file in the database.

            def download():
                return response.download(request, db)
        #downloads from http://..../download/filename

response.download() takes request to extract from it the file name stored in [request.args]

download function is mainly used by SQLFORM to update a record that includes an upload field that is used to upload an image, in this case response.download() gets the file (image) to be displayed when updating this record.

form = SQLFORM(db.my_table, record, upload=URL(r=request, c='default', f='download'))

Suppose you want to stream an MP3 file, you can do something like:

Somebody asked how to stream an mp3 file from the uploads files directly:
def get_my_file():
      filename=request.args[0]
      path=os.path.join(request.folder,'uploads',filename)
      response.headers['ContentType'] ="application/octet-stream";
      response.headers['Content-Disposition']="attachment; filename="  
+filename
      return response.stream(open(filename),chunk_size=4096)

IS_IN_SET with or without combo box !!

Look at this piece of code :

CURRENCY_SET = [
                   T('EGP'),
                   T('EUR'),
                   T('USD')

                ]
db.define_table('service',
                Field('name', 'string', label=T('Name')),
                Field('description', 'string', label=T('Description')),
                Field('price', 'double', label=T('Price')),
                Field('currency', 'string', required=True,
                      requires=[
                                IS_IN_SET(CURRENCY_SET, zero=T('--choose currency--'))
                                ]

                                ),

                Field('image', 'upload', label=T('Photo'))

                )

You expect it to get you a combo box in your field to choose among different currencies in your system
but it doesn’t offer you that , it just give you a Normal text field that you should enter in it the currency
and will not accept values except ‘EGP’, ‘EUR’, or ‘USD’

So what’s wrong and how can I get the combo box that I want ?

Simply, when you want IS_IN_SET to get you a combo box , don’t use it like this :

requires=[IS_IN_SET(CURRENCY_SET, zero=T('--choose currency--'))]

instead use :

requires=IS_IN_SET(CURRENCY_SET, zero=T('--choose currency--'))

Tricky hah ?  😀

Any way there’s a solution for this, please refer to This post