Parse multipart request string in Python

Question

I have a string like this

\"--5b34210d81fb44c5a0fdc1a1e5ce42c3\\r\\nContent-Disposition: form-data; name=\\\"author\\\"\\r\\n\\r\\nJohn Smith\\r\\n--5b34210d         


        

Answer 1

If using CGI, I recommend using FieldStorage:

from cgi import FieldStorage

fs = FieldStorage(fp=event['body'], headers=event['headers'], environ={'REQUEST_METHOD':'POST', 'CONTENT_TYPE':event['headers']['Content-Type'], })['file']
originalFileName = fs.filename
binaryFileData = fs.file.read()

see also: https://stackoverflow.com/a/38718958/10913265

If the event body contains multiple files:

fs = FieldStorage(fp=event['body'], headers=event['headers'], environ={'REQUEST_METHOD':'POST', 'CONTENT_TYPE':event['headers']['Content-Type'], })['file']

delivers a list of FieldStorage objects. So you can do:

for f in fs:
    originalFileName = f.filename
    binaryFileData = f.file.read()

Altogether my solution for dealing with a single file as well as multiple files as well as a body containing no file and assuring that it was mutlipart/form-data:

from cgi import parse_header, FieldStorage

#see also: https://stackoverflow.com/a/56405982/10913265
c_type, c_data = parse_header(event['headers']['Content-Type'])
assert c_type == 'multipart/form-data'

#see also: https://stackoverflow.com/a/38718958/10913265
fs = FieldStorage(fp=event['body'], headers=event['headers'], environ={'REQUEST_METHOD':'POST', 'CONTENT_TYPE':event['headers']['Content-Type'], })['file']

#If fs contains a single file or no file: making FieldStorage object to a list, so it gets iterable
if not(type(fs) == list):
    fs = [fs]

for f in fs:
    originalFileName = f.filename
    #no file: 
    if originalFileName == '':
        continue
    binaryFileData = f.file.read()
    #Do something with the data