Why postgresql on mac asks me for password after fresh install?

Question

I just installed postgresql on a Macbook with brew install postgresql. Then I try to psql, but it requires password and then show

Answer 1

The answer by Pramida almost worked for me... the difference is I was using 9.6 Postgres.

So I ran:

sudo /Library/PostgreSQL/9.6/uninstall-postgresql.app/Contents/MacOS/installbuilder.sh

and somehow that got rid of my username and almost all of postgres user. I think

I then blew away the directory

sudo rm -rf /Library/PostgreSQL/9.6

And then I installed using brew above.