This works great! I looked into doi.org before but I wasn't sure what their ratelimit is. I'm currently using phantomJS and google scholar for DOIs, and I think I might have hit their rate limit already, so I will take a second look at this!
Any questions email, us at labs@crossref.org
*which are the kinds of DOI you're likely to be citing, but other Registration Agencies and types of DOIs exist
import requests
import json
url = 'http://data.crossref.org/10.1017/S0022112061000019'
headers = {'Accept': 'application/citeproc+json'}
r = requests.get(url, headers=headers)
meta = json.loads(r.content)
# meta is a dictionary of metadata, e.g. meta['DOI'] meta = r.json()