Is there any simple way to store the user location while registering in database
Not in any reliable way, or at least not in Django. The problem is that user IPs are usually dynamic, hence the address is changing every couple of days. Also some ISPs soon will start to use a single IP for big blocks of users (forgot what this is called) since they are running out of IPv4 IP addresses... In other words, all users from that ISP within a whole state or even country will have a single IP address.
So using the IP is not reliable. You could probably figure out the country or region of the user with reasonable accuracy however my recommendation is not to use the IP for anything except logging and permission purposes (e.g. blocking a spam IP).
If you want user locations, you can however use HTML5 location API which will have a much better shot of getting more accurate location since it can utilize other methods such us using a GPS sensor in a phone.
I have the user registration form made in django.
I want to know the city from which the user is registering.
Is there any way that i get the IP address of the user and then somehow get the city for that IP. using some API or something