Option 1
You can directly import contacts from your Yahoo Mail Account by logging in your yahoo account using Option 1 below or you can follow the steps in Option 2 to manually import your contacts from your Yahoo Address Book.

Option 2
Now, to export your Gmail address book to a csv file: Follow the steps below to manually import your GMail Address Book Contacts in a .csv file.
The first step is to log in to your Gmail account and notice that down the left side of the screen is a list of your folders (Inbox, Starred, Sent Mail, etc) and, just below it, Contacts. Click on that.
Now you're looking at a page that shows you a list of frequently mailed contacts and has a second tab for Al Contacts. On the top of that page, you'll see this:
Notice the rightmost option: export. Click on that and you'll see a helpful pop-up window:

I declare that the email addresses provided in the CSV file are from my own email accounts