Curl POST request into pycurl code

Question

I'm trying to convert following curl request into pycurl:

curl -v
-H Accept:application/json \
-H Content-Type:application/json \
-d "{
    name: 'abc',
    path: 'def',
    target: [ 'ghi' ]
}" \
-X POST http://some-url

I have following python code:

import pycurl, json

c = pycurl.Curl()
c.setopt(pycurl.URL, 'http://some-url')
c.setopt(pycurl.HTTPHEADER, ['Accept: application/json'])
data = json.dumps({"name": "abc", "path": "def", "target": "ghi"})
c.setopt(pycurl.POST, 1)
c.setopt(pycurl.POSTFIELDS, data)
c.setopt(pycurl.VERBOSE, 1)
c.perform()
print curl_agent.getinfo(pycurl.RESPONSE_CODE)
c.close()

Executing this I had an error 415: Unsupported media type, so I have changed:

c.setopt(pycurl.HTTPHEADER, ['Accept: application/json'])

into:

c.setopt(pycurl.HTTPHEADER, [ 'Content-Type: application/json' , 'Accept: application/json'])

This time I have 400: Bad request. But bash code with curl works. Do you have any idea what should I fix in python code?

Answer 1

In your bash example, the property target is an array, in your Python example it is a string.

Try this:

data = json.dumps({"name": "abc", "path": "def", "target": ["ghi"]})

I also strongly advise you to check out the requests library which has a much nicer API:

import requests
data = {"name": "abc", "path": "def", "target": ["ghi"]}
response = requests.post('http://some-url', json=data)
print response.status_code

Answer 2

PycURL is a wrapper on the libcurl library written in C language so its Python API can be bit puzzling. As some people are advocating use of python requests instead I just want to point out that it isn't a perfect replacement. For me, its lack of DNS resolution timeout was a deal breaker. I also find it much slower on my Raspberry Pi. This comparison may be relevant: Python Requests vs PyCurl Performance

So here's something that doesn't evade OP's question:

import pycurl
import json
from cStringIO import StringIO

curl = pycurl.Curl()
curl.setopt(pycurl.URL, 'http://some-url')
curl.setopt(pycurl.HTTPHEADER, ['Accept: application/json',
                                'Content-Type: application/json'])
curl.setopt(pycurl.POST, 1)

# If you want to set a total timeout, say, 3 seconds
curl.setopt(pycurl.TIMEOUT_MS, 3000)

## depending on whether you want to print details on stdout, uncomment either
# curl.setopt(pycurl.VERBOSE, 1) # to print entire request flow
## or
# curl.setopt(pycurl.WRITEFUNCTION, lambda x: None) # to keep stdout clean

# preparing body the way pycurl.READDATA wants it
# NOTE: you may reuse curl object setup at this point
#  if sending POST repeatedly to the url. It will reuse
#  the connection.
body_as_dict = {"name": "abc", "path": "def", "target": "ghi"}
body_as_json_string = json.dumps(body_as_dict) # dict to json
body_as_file_object = StringIO(body_as_json_string)

# prepare and send. See also: pycurl.READFUNCTION to pass function instead
curl.setopt(pycurl.READDATA, body_as_file_object) 
curl.setopt(pycurl.POSTFIELDSIZE, len(body_as_json_string))
curl.perform()

# you may want to check HTTP response code, e.g.
status_code = curl.getinfo(pycurl.RESPONSE_CODE)
if status_code != 200:
    print "Aww Snap :( Server returned HTTP status code {}".format(status_code)

# don't forget to release connection when finished
curl.close()

There are some more interesting features worth checking out in the libcurl curleasy setopts documentation