def __init__(self, db_name, db_url='<STR_LIT>',<EOL>username=None, password=None, readonly=False, autocreate=True,<EOL>timeout=<NUM_LIT>, verify_ssl_cert=True):
self.db_name = db_name<EOL>self.db_url = db_url<EOL>self.readonly = False<EOL>self.timeout = timeout<EOL>self.request_session = requests.Session()<EOL>self.request_session.verify = verify_ssl_cert<EOL>if username:<EOL><INDENT>self.request_session.auth = (username, password or '<STR_LIT>')<EOL><DEDENT>self.settings = {}<EOL>self.db_exists = False <EOL>self.db_exists = self._is_existing_database()<EOL>if readonly:<EOL><INDENT>if not self.db_exists:<EOL><INDENT>raise DatabaseException('<STR_LIT>')<EOL><DEDENT>self.connection_readonly = self._is_connection_readonly()<EOL>self.readonly = True<EOL><DEDENT>elif autocreate and not self.db_exists:<EOL><INDENT>self.create_database()<EOL><DEDENT>self.server_version = self._get_server_version()<EOL>self.server_timezone = self._get_server_timezone() if self.server_version > (<NUM_LIT:1>, <NUM_LIT:1>, <NUM_LIT>) else pytz.utc<EOL>
Initializes a database instance. Unless it's readonly, the database will be
created on the ClickHouse server if it does not already exist.

- `db_name`: name of the database to connect to.
- `db_url`: URL of the ClickHouse server.
- `username`: optional connection credentials.
- `password`: optional connection credentials.
- `readonly`: use a read-only connection.
- `autocreate`: automatically create the database if it does not exist (unless in readonly mode).
- `timeout`: the connection timeout in seconds.
- `verify_ssl_cert`: whether to verify the server's certificate when connecting via HTTPS.