Can a python script on my server access the webcam and audio input of a user as easily and as well as a Flash plugin can?
No: the "plugin" you mention runs in the user's browser, your server-side script (Python or otherwise) runs on the server, a completely different proposition.  This relates to your other recent question about a server-side script accessing information on your desktop: your client machine tends to be very protected against possibly malicious server-side apps (never enough, but everybody keeps trying to make it more and more protected these days).
Python access webcam and audio input