express.QueryChat

express.QueryChat(
    data_source=None,
    table_name=None,
    *,
    id=None,
    greeting=None,
    client=None,
    tools=DEFAULT_TOOLS,
    data_dict=None,
    extra_instructions=None,
    prompt_template=None,
    categorical_threshold=20,
    data_description=None,
    enable_bookmarking='auto',
)

Use QueryChat with Shiny Express.

This class makes it easy to use querychat within Shiny Express apps – it automatically calls .server() during initialization, so you don’t have to do it manually.

Examples

from querychat.express import QueryChat
from seaborn import load_dataset
from shiny.express import app_opts, render, ui

titanic = load_dataset("titanic")

qc = QueryChat(titanic, "titanic")
qc.sidebar()

with ui.card(fill=True):
    with ui.card_header():

        @render.text
        def title():
            return qc.title() or "Titanic Dataset"

    @render.data_frame
    def data_table():
        return qc.df()


ui.page_opts(
    title="Titanic QueryChat App",
    fillable=True,
)

app_opts(bookmark_store="url")

Parameters

Name	Type	Description	Default
data_source	`IntoFrame` \| `sqlalchemy`.`Engine` \| `ibis`.`Table` \| None	Either a Narwhals-compatible data frame (e.g., Polars or Pandas) or a SQLAlchemy engine containing the table to query against. Can be `None` for deferred binding (set via the `data_source` property before the real session starts).	`None`
table_name	str \| None	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.	`None`
id	Optional[str]	An optional ID for the QueryChat module. If not provided, an ID will be generated based on the table_name.	`None`
greeting	Optional[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()`. You can use `querychat.greeting()` to help generate a greeting from a querychat configuration. If no greeting is provided, one will be generated at the start of every new conversation.	`None`
client	Optional[str \| `chatlas`.`Chat`]	A `chatlas.Chat` object or a string to be passed to `chatlas.ChatAuto()`’s `provider_model` parameter, describing the provider and model combination to use (e.g. `"openai/gpt-4.1"`, “anthropic/claude-sonnet-4-5”, “google/gemini-2.5-flash”. etc). If `client` is not provided, querychat consults the `QUERYCHAT_CLIENT` environment variable. If that is not set, it defaults to `"openai"`.	`None`
data_dict	`DataDict` \| str \| Path \| None	A :class:`~querychat.DataDict` instance, or a path (`str` or `pathlib.Path`) to a YAML file, that provides rich per-table and per-column metadata. When set, documented columns use the dict’s `values`, `range`, and `description` fields instead of querying the data source for statistics, which speeds up schema generation and improves LLM context. Supersedes `data_description`.	`None`
extra_instructions	Optional[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	Optional[str \| 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`
categorical_threshold	int	Threshold for determining if a column is categorical based on number of unique values.	`20`
data_description	Optional[str \| Path]	Optional plain-text or Markdown description of the data, as a string or file path. Superseded by `data_dict` for new code.	`None`

Attributes

Name	Description
data_source	Removed. Use `add_table()` and `remove_table()` to manage tables.
greeter	Greeting configuration and generator for this QueryChat instance.
system_prompt	Get the system prompt.

Methods

Name	Description
add_table	Add or replace a table in the QueryChat instance.
add_tables	Add multiple tables from a SQLAlchemy engine or Ibis backend in a single call.
cleanup	Clean up resources associated with all data sources.
client	Create a chat client with registered tools.
console	Launch an interactive console chat with the data.
current_table	Reactively read the name of the most recently queried table.
df	Reactively read the current filtered data frame that is in effect.
generate_greeting	Generate a welcome greeting for the chat.
remove_table	Remove a table from the QueryChat instance.
sidebar	Create a sidebar containing the querychat UI.
sql	Reactively read (or set) the current SQL query that is in effect.
table	Get a per-table accessor with reactive state.
table_names	Return the names of all registered tables.
title	Reactively read (or set) the current title that is in effect.
ui	Create the UI for the querychat component.

add_table

express.QueryChat.add_table(
    data_source,
    table_name,
    *,
    replace=False,
    include_in_greeting=False,
)

Add or replace a table in the QueryChat instance.

Parameters

Name	Type	Description	Default
data_source	`IntoFrame` \| `sqlalchemy`.`Engine` \| `BaseBoard`	The data source (DataFrame, LazyFrame, database connection, or pins board).	required
table_name	str	Name for the table.	required
replace	bool	If True, replace an existing table with the same name. If False (default), raise ValueError if the table already exists.	`False`
include_in_greeting	bool	If True, include this table’s schema in the greeting system prompt.	`False`

Raises

Name	Type	Description
	TypeError	If include_in_greeting is not a bool.
	ValueError	If table_name already exists (and replace=False) or is invalid.
	RuntimeError	If called after server() has been invoked.

add_tables

express.QueryChat.add_tables(
    data_source,
    tables=None,
    *,
    replace=False,
    include_in_greeting=False,
)

Add multiple tables from a SQLAlchemy engine or Ibis backend in a single call.

Unlike calling :meth:add_table repeatedly, this method builds the system prompt exactly once after all tables have been staged, avoiding N-1 spurious intermediate rebuilds.

Parameters

Name	Type	Description	Default
data_source	`sqlalchemy`.`Engine` \| `SQLBackend`	A SQLAlchemy engine or Ibis SQL backend. Pass individual DataFrames or other sources via :meth:`add_table`.	required
tables	list[str] \| None	Table names to register. When `None`, all tables returned by the backend’s table-discovery method are used.	`None`
replace	bool	If `True`, replace any existing table whose name appears in `tables`. If `False` (default), raise `ValueError` if any name already exists.	`False`
include_in_greeting	bool \| list[str]	`True` to include all added tables in the greeting, `False` (default) for none, or a list of table names to include. Any other type raises `TypeError`.	`False`

Raises

Name	Type	Description
	TypeError	If `data_source` is not a `sqlalchemy.Engine` or Ibis SQL backend.
	ValueError	If the resolved table list is empty, any name is invalid, or any name already exists (and `replace=False`).
	RuntimeError	If called after :meth:`server` has been invoked.

Examples

>>> qc = QueryChat()
>>> qc.add_tables(engine)

>>> qc.add_tables(engine, ["orders", "customers"])

>>> import ibis
>>> backend = ibis.duckdb.connect("mydb.duckdb")
>>> qc.add_tables(backend)

cleanup

express.QueryChat.cleanup()

Clean up resources associated with all data sources.

client

express.QueryChat.client(
    tools=MISSING,
    update_dashboard=None,
    reset_dashboard=None,
    visualize=None,
)

Create a chat client with registered tools.

Parameters

Name	Type	Description	Default
tools	`TOOL_GROUPS` \| tuple[`TOOL_GROUPS`, …] \| None \| `MISSING_TYPE`	Which tools to include: `"filter"`, `"query"`, `"visualize"`, or a combination. The legacy name `"update"` is still accepted as an alias for `"filter"`.	`MISSING`
update_dashboard	Callable[[`UpdateDashboardData`], None] \| None	Callback when update_dashboard tool succeeds.	`None`
reset_dashboard	`ResetDashboardCallback` \| None	Callback when reset_dashboard tool is invoked.	`None`
visualize	Callable[[`VisualizeData`], None] \| None	Callback when visualize tool succeeds.	`None`

Returns

Name	Type	Description
	`chatlas`.`Chat`	A configured chat client.

console

express.QueryChat.console(new=False, tools='query', **kwargs)

Launch an interactive console chat with the data.

current_table

express.QueryChat.current_table()

Reactively read the name of the most recently queried table.

Returns None if no query has run yet in this session. Useful for auto-switching a tabbed UI to the active table.

Returns

Name	Type	Description
	str or None	Table name, or `None`.

df

express.QueryChat.df()

Reactively read the current filtered data frame that is in effect.

Returns

Name	Type	Description
	`IntoFrameT`	The current filtered data frame, in the same format as the original data source (e.g., polars DataFrame, Polars LazyFrame, Ibis Table). If no query has been set, returns the unfiltered data from the data source.

generate_greeting

express.QueryChat.generate_greeting(echo='none')

Generate a welcome greeting for the chat.

remove_table

express.QueryChat.remove_table(table_name)

Remove a table from the QueryChat instance.

Parameters

Name	Type	Description	Default
table_name	str	Name of the table to remove.	required

Raises

Name	Type	Description
	ValueError	If table doesn’t exist or is the last remaining table.
	RuntimeError	If called after server() has been invoked.

sidebar

express.QueryChat.sidebar(
    width=400,
    height='100%',
    fillable=True,
    id=None,
    **kwargs,
)

Create a sidebar containing the querychat UI.

Parameters

Name	Type	Description	Default
width	int	Width of the sidebar in pixels.	`400`
height	str	Height of the sidebar.	`'100%'`
fillable	bool	Whether the sidebar should be fillable. Default is `True`.	`True`
id	Optional[str]	Optional ID for the QueryChat instance. If not provided, will use the ID provided at initialization.	`None`
**kwargs		Additional arguments passed to `shiny.ui.sidebar()`.	`{}`

Returns

Name	Type	Description
	ui.`Sidebar`	A sidebar UI component.

sql

express.QueryChat.sql(query=None)

Reactively read (or set) the current SQL query that is in effect.

Parameters

Name	Type	Description	Default
query	Optional[str]	If provided, sets the current SQL query to this value.	`None`

Returns

Name	Type	Description
	str \| None \| bool	If no `query` is provided, returns the current SQL query as a string (or `None` if no query has been set). If a `query` is provided, returns `True` if the query was changed to a new value, or `False` if it was the same as the current value.

table

express.QueryChat.table(name)

Get a per-table accessor with reactive state.

Parameters

Name	Type	Description	Default
name	str	Table name (must match a name passed to `add_table()`).	required

Returns

Name	Type	Description
	`TableAccessor`	Accessor with `df()`, `sql()`, and `title()` backed by per-session reactive state.

Examples

from querychat.express import QueryChat
from shiny.express import render

qc = QueryChat(orders, "orders")
qc.add_table(customers, "customers")
qc.sidebar()


@render.data_frame
def orders_table():
    return qc.table("orders").df()


@render.data_frame
def customers_table():
    return qc.table("customers").df()

table_names

express.QueryChat.table_names()

Return the names of all registered tables.

Returns

Name	Type	Description
	list[str]	List of table names in the order they were added.

title

express.QueryChat.title(value=None)

Reactively read (or set) the current title that is in effect.

The title is a short description of the current query that the LLM provides to us whenever it generates a new SQL query. It can be used as a status string for the data dashboard.

Parameters

Name	Type	Description	Default
value	Optional[str]	If provided, sets the current title to this value.	`None`

Returns

Name	Type	Description
	str \| None \| bool	If no `value` is provided, returns the current title as a string, or `None` if no title has been set due to no SQL query being set. If a `value` is provided, sets the current title to this value and returns `True` if the title was changed to a new value, or `False` if it was the same as the current value.

ui

express.QueryChat.ui(id=None, **kwargs)

Create the UI for the querychat component.

Parameters

Name	Type	Description	Default
id	Optional[str]	Optional ID for the QueryChat instance. If not provided, will use the ID provided at initialization.	`None`
**kwargs		Additional arguments to pass to `shinychat.chat_ui()`.	`{}`

Returns

Name	Type	Description
		A UI component.