Python - Parsing multipart/form-data request on server side

Question

Im trying to do a http 'POST' with multipart/form-data to a python GAE backend. My server side method is receiving the complete body but i have absolutely no idea how to parse the body content without going over it manually and splitting the text for values.

My request looks like this:

POST /android/v4/MyPostMethod HTTP/1.1
Accept: */*
Accept-Charset: *
Content-Length: 186808
Content-Type: multipart/form-data; boundary=*****; charset="utf-8"
Content_Length: 186808
Content_Type: multipart/form-data; boundary=*****
Host: myhost.appspot.com
User-Agent: Dalvik/1.6.0 (Linux; U; Android 4.1.2; GT-I9300 Build/XXXXX)
Via: HTTP/1.1 MSP-YV

--*****
Content-Disposition: form-data; name="value1"
Content-Type: text/plain; charset=UTF-8

f0ef73c5-54dd-40cf-9ee7-5c4cb764eb28
--*****
Content-Disposition: form-data; name="value2"
Content-Type: text/plain; charset=UTF-8

10d71e73-4d4d-4607-b271-f7efcfd0c59d
--*****
Content-Disposition: form-data; name="value3"
Content-Type: text/plain; charset=UTF-8

10d71e73-4d4d-4607-b271-f7efdfdfdfdf
--*****
Content-Disposition: form-data; name="logText"; filename="log.txt"
Content-Type: text/plain
Content-Transfer-Encoding: binary

xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx
xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx
xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx
xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx
...
--*****--

I've searched around and couldn't find a good explanation of how to do this trivial thing. Appreciate if someone could help me here. Thanks.

AsafK · Accepted Answer · 2014-09-07 14:46:29Z

7

For some reason cgi.FieldStorage() wasnt working for me, but only the deprecated method :

pdict = {'boundary':'*****'}
cgi.parse_multipart(self.request.body_file, pdict)

Dont know why but as long as its working im fine with that.

edited Sep 7, 2014 at 14:46

answered Sep 5, 2014 at 21:35

AsafK

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1 Comment

mbarkhau Over a year ago

This is not ideal for large files. From the documentation "This is easy to use but not much good if you are expecting megabytes to be uploaded — in that case, use the FieldStorage class instead which is much more flexible."

user1743173 · Accepted Answer · 2014-09-03 13:19:33Z

0

You want the .cgi python library.

Specifically something like this:

import cgi
form = cgi.FieldStorage() 
value1 = form.getfirst("value1", "")
value2 = form.getfirst("value2", "") 
value3 = form.getfirst("value3", "") 
logtext = form.getfirst("logText", "")

answered Sep 3, 2014 at 13:19

user1743173

Comments

Niklas Rosencrantz · Accepted Answer · 2019-01-04 07:40:31Z

-1

If you want the uploaded files, you can do this

for upload in self.get_uploads():

If you want just a text field:

x = self.request.get('value1')

answered Jan 4, 2019 at 7:40

Niklas Rosencrantz

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