connect to a DB using psycopg2 without password
Surprisingly, the answer is to not specify a host at all. If you do this,
DATABASES = { 'default': { 'ENGINE': 'django.db.backends.postgresql_psycopg2', 'NAME': 'mwt', }}Then psycopg2 will connect using a Unix socket in the same manner as psql. When you specify a HOST, psycopg2 will connect with TCP/IP, which requires a password.
To avoid using a password in Django settings.py change md5 to trust in this line of pg_hba.conf:
host all all 127.0.0.1/32 trustFor a detailed understanding of the postgres security configurations read this doc.
To locate this file:
sudo -u postgres psql -c 'SHOW hba_file;'
Check your pg_hba.conf to allow connection from localhost by user shaoran, then either provide the password of shaoran in Django settings or trust the user in pg_hba.conf
The fact that you could connect through psql is because psql -d mwt uses some default connection values which are set as trusted in pg_hba.conf. For example, on my machine, the default host is local socket instead of localhost