Accessing an on-premises Dynamics 365 organization from Python

I've previously showed how to access online and IFD instances of Dynamics 365 Customer Engagement from Python code. Because that sample code authenticated to the Web API using OAuth, it won't work with on-premises instances. Recently I've been doing some work with Python and an on-premises Dynamics 365 organization, so I thought I'd share a sample that shows how to authenticate to the Web API using NTLM.

import requests
from requests_ntlm import HttpNtlmAuth
import json

username = 'companyx\\administrator'
userpassword = 'PASSWORD GOES HERE'

#set these values to query your crm data
crmwebapi = 'http://33.0.0.16/lucastest02/api/data/v8.1'
crmwebapiquery = '/contacts?$select=fullname,contactid'

crmrequestheaders = {
    'OData-MaxVersion': '4.0',
    'OData-Version': '4.0',
    'Accept': 'application/json',
    'Content-Type': 'application/json; charset=utf-8',
    'Prefer': 'odata.maxpagesize=500',
    'Prefer': 'odata.include-annotations=OData.Community.Display.V1.FormattedValue'
}

print('making crm request . . .')
crmres = requests.get(crmwebapi+crmwebapiquery, headers=crmrequestheaders,auth=HttpNtlmAuth(username,userpassword))
print('crm response received . . .')
try:
    print('parsing crm response . . .')
    crmresults = crmres.json()
    for x in crmresults['value']:
        print (x['fullname'] + ' - ' + x['contactid'])
except KeyError:
    print('Could not parse CRM results')

As you can see, this code doesn't retrieve an OAuth token before calling the Dynamics 365 Web API, but rather it uses the requests-ntlm package to authenticate directly to the Web API using a username and password. Other than that small change, everything else works the same as in my previous examples.