The [client] group does not normally include the database name, and including it will prevent mysqldump (and other services) from running.

Typically the database is set under the [mysql] group.

Without causing much trouble to existing code, the read_default_group switch could accept a tuple of groups (eg ('client','mysql'). However, the underlying configparser only allows a single default group. (Py2 ConfigParser doesn't allow one to set a default group, but one can set default values).

So, the default group should be 'client' and, following https://dev.mysql.com/doc/refman/8.0/en/option-files.html#option-file-syntax (and the way in which mysql cli works), and unless otherwise specified, the group should be '[pymysql]' (The application name), with the default group being [client].