sendFbMessage.py

def send_message(recipient_id, message_text):
#setting the parameters for the request
    params = {
        "access_token": os.environ["PAGE_ACCESS_TOKEN"]
      #another way you can do this is
      # "access_token": "YOUR PAGE ACCESS TOKEN"
    }
    headers = {
        "Content-Type": "application/json"
    }
    data = json.dumps({
        "recipient": {
            "id": recipient_id
        },
        "message": {
            "text": message_text
        }
    })
    r = requests.post("https://graph.facebook.com/v2.6/me/messages", params=params, headers=headers, data=data)
    if r.status_code != 200:
        print("Succesfully sent the message")