init

init(
    data_source,
    table_name,
    *,
    greeting=None,
    data_description=None,
    extra_instructions=None,
    prompt_template=None,
    system_prompt_override=None,
    client=None,
    create_chat_callback=None,
)

Initialize querychat with any compliant data source.

Parameters

Name	Type	Description	Default
data_source	IntoFrame | sqlalchemy.Engine	Either a Narwhals-compatible data frame (e.g., Polars or Pandas) or a SQLAlchemy engine containing the table to query against.	required
table_name	str	If a data_source is a data frame, a name to use to refer to the table in SQL queries (usually the variable name of the data frame, but it doesn’t have to be). If a data_source is a SQLAlchemy engine, the table_name is the name of the table in the database to query against.	required
greeting	str | Path	A string in Markdown format, containing the initial message. If a pathlib.Path object is passed, querychat will read the contents of the path into a string with .read_text().	None
data_description	str | Path	Description of the data in plain text or Markdown. If a pathlib.Path object is passed, querychat will read the contents of the path into a string with .read_text().	None
extra_instructions	str | Path	Additional instructions for the chat model. If a pathlib.Path object is passed, querychat will read the contents of the path into a string with .read_text().	None
prompt_template	Path	Path to or a string of a custom prompt file. If not provided, the default querychat template will be used. This should be a Markdown file that contains the system prompt template. The mustache template can use the following variables: - {db_engine}: The database engine used (e.g., “DuckDB”) - {schema}: The schema of the data source, generated by data_source.get_schema() - {data_description}: The optional data description provided - {extra_instructions}: Any additional instructions provided	None
system_prompt_override	str	A custom system prompt to use instead of the default. If provided, data_description, extra_instructions, and prompt_template will be silently ignored.	None
client	(chatlas.Chat, CreateChatCallback, str)	A chatlas.Chat object, a string to be passed to chatlas.ChatAuto() describing the model to use (e.g. "openai/gpt-4.1"), or a function that creates a chat client. If using a function, the function should accept a system_prompt argument and return a chatlas.Chat object. If client is not provided, querychat consults the QUERYCHAT_CLIENT environment variable, which can be set to a provider-model string. If no option is provided, querychat defaults to using chatlas.ChatOpenAI(model="gpt-4.1").	None
create_chat_callback	CreateChatCallback	Deprecated. Use the client argument instead.	None

Returns

Name	Type	Description
	QueryChatConfig	A QueryChatConfig object that can be passed to server()