For example username and password in 
r = requests.post( loginUrl, data = {'username':'myuser', 'password':'mypw'} )
are from attribute name on the web site element. The information to post is given in parameter data with a dictionary.
It has a key username with a value myuser. The key username is taken from an element on a website with attribute name, means the key is taken from a key-value. By default requests select attribute name for the key. 
To clarify this here is a html code snippet:
<form name="login" id="form1" method="post" action="http://mylogin.net">
  Username: <input name="username" id="input1" type="text" /><br/>
  Password: <input name="password" id="input2" type="password" /><br/>
  <input type="submit" value="OK" />
</form>
I prefer to use the id attribute as key because it is unique on the web page.
How can I select attribute id instead of default name to get the key for the post in requests, so I can use
r = requests.post( loginUrl, data = {'input1':'myuser', 'input2':'mypw'} ) ?
 
    