requests.post参数中json vs data

在源码中的prepare_body方法中，如果发现json参数，会默认为hearders为Content-Type:application/json.

def prepare_body(self, data, files, json=None):
        """Prepares the given HTTP body data."""

        # Check if file, fo, generator, iterator.
        # If not, run through normal process.

        # Nottin' on you.
        body = None
        content_type = None

        if not data and json is not None:
            # urllib3 requires a bytes-like body. Python 2's json.dumps
            # provides this natively, but Python 3 gives a Unicode string.
            content_type = 'application/json'
            body = complexjson.dumps(json)
            if not isinstance(body, bytes):
                body = body.encode('utf-8')
        ...

(调用同事的api时，发现了这个问题，记录一下，省去json.dumps(params)的步骤)