# Copyright (c) Streamlit Inc. (2018-2022) Snowflake Inc. (2022-2025) # # Licensed under the Apache License, Version 2.0 (the "License"); # you may not use this file except in compliance with the License. # You may obtain a copy of the License at # # http://www.apache.org/licenses/LICENSE-2.0 # # Unless required by applicable law or agreed to in writing, software # distributed under the License is distributed on an "AS IS" BASIS, # WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. # See the License for the specific language governing permissions and # limitations under the License. from __future__ import annotations from textwrap import dedent from typing import TYPE_CHECKING, Any, Callable, Generic, Literal, cast, overload from streamlit.dataframe_util import OptionSequence, convert_anything_to_list from streamlit.elements.lib.form_utils import current_form_id from streamlit.elements.lib.options_selector_utils import ( create_mappings, index_, maybe_coerce_enum, ) from streamlit.elements.lib.policies import ( check_widget_policies, maybe_raise_label_warnings, ) from streamlit.elements.lib.utils import ( Key, LabelVisibility, compute_and_register_element_id, get_label_visibility_proto_value, save_for_app_testing, to_key, ) from streamlit.errors import StreamlitAPIException from streamlit.proto.Selectbox_pb2 import Selectbox as SelectboxProto from streamlit.runtime.metrics_util import gather_metrics from streamlit.runtime.scriptrunner import ScriptRunContext, get_script_run_ctx from streamlit.runtime.state import ( WidgetArgs, WidgetCallback, WidgetKwargs, get_session_state, register_widget, ) from streamlit.type_util import ( T, check_python_comparable, ) if TYPE_CHECKING: from collections.abc import Sequence from streamlit.delta_generator import DeltaGenerator class SelectboxSerde(Generic[T]): options: Sequence[T] formatted_options: list[str] formatted_option_to_option_index: dict[str, int] default_option_index: int | None def __init__( self, options: Sequence[T], *, formatted_options: list[str], formatted_option_to_option_index: dict[str, int], default_option_index: int | None = None, ): """Initialize the SelectboxSerde. We do not store an option_to_formatted_option mapping because the generic options might not be hashable, which would raise a RuntimeError. So we do two lookups: option -> index -> formatted_option[index]. Parameters ---------- options : Sequence[T] The sequence of selectable options. formatted_options : list[str] The string representations of each option. The formatted_options correspond to the options sequence by index. formatted_option_to_option_index : dict[str, int] A mapping from formatted option strings to their corresponding indices in the options sequence. default_option_index : int or None, optional The index of the default option to use when no selection is made. If None, no default option is selected. """ self.options = options self.formatted_options = formatted_options self.formatted_option_to_option_index = formatted_option_to_option_index self.default_option_index = default_option_index def serialize(self, v: T | str | None) -> str | None: if v is None: return None if len(self.options) == 0: return "" # we don't check for isinstance(v, str) because this could lead to wrong # results if v is a string that is part of the options itself as it would # skip formatting in that case try: option_index = index_(self.options, v) return self.formatted_options[option_index] except ValueError: # we know that v is a string, otherwise it would have been found in the # options return cast("str", v) def deserialize( self, ui_value: str | None, widget_id: str = "", ) -> T | str | None: # check if the option is pointing to a generic option type T, # otherwise return the option itself if ui_value is None: return ( self.options[self.default_option_index] if self.default_option_index is not None and len(self.options) > 0 else None ) option_index = self.formatted_option_to_option_index.get(ui_value) return self.options[option_index] if option_index is not None else ui_value class SelectboxMixin: @overload def selectbox( self, label: str, options: OptionSequence[T], index: int = 0, format_func: Callable[[Any], str] = str, key: Key | None = None, help: str | None = None, on_change: WidgetCallback | None = None, args: WidgetArgs | None = None, kwargs: WidgetKwargs | None = None, *, # keyword-only arguments: placeholder: str | None = None, disabled: bool = False, label_visibility: LabelVisibility = "visible", accept_new_options: Literal[False] = False, ) -> T: ... @overload def selectbox( self, label: str, options: OptionSequence[T], index: int = 0, format_func: Callable[[Any], str] = str, key: Key | None = None, help: str | None = None, on_change: WidgetCallback | None = None, args: WidgetArgs | None = None, kwargs: WidgetKwargs | None = None, *, # keyword-only arguments: placeholder: str | None = None, disabled: bool = False, label_visibility: LabelVisibility = "visible", accept_new_options: Literal[True] = True, ) -> T | str: ... @overload def selectbox( self, label: str, options: OptionSequence[T], index: None, format_func: Callable[[Any], str] = str, key: Key | None = None, help: str | None = None, on_change: WidgetCallback | None = None, args: WidgetArgs | None = None, kwargs: WidgetKwargs | None = None, *, # keyword-only arguments: placeholder: str | None = None, disabled: bool = False, label_visibility: LabelVisibility = "visible", accept_new_options: Literal[False] = False, ) -> T | None: ... @overload def selectbox( self, label: str, options: OptionSequence[T], index: None, format_func: Callable[[Any], str] = str, key: Key | None = None, help: str | None = None, on_change: WidgetCallback | None = None, args: WidgetArgs | None = None, kwargs: WidgetKwargs | None = None, *, # keyword-only arguments: placeholder: str | None = None, disabled: bool = False, label_visibility: LabelVisibility = "visible", accept_new_options: Literal[True] = True, ) -> T | str | None: ... @overload def selectbox( self, label: str, options: OptionSequence[T], index: int | None = 0, format_func: Callable[[Any], str] = str, key: Key | None = None, help: str | None = None, on_change: WidgetCallback | None = None, args: WidgetArgs | None = None, kwargs: WidgetKwargs | None = None, *, # keyword-only arguments: placeholder: str | None = None, disabled: bool = False, label_visibility: LabelVisibility = "visible", accept_new_options: bool = False, ) -> T | str | None: ... @gather_metrics("selectbox") def selectbox( self, label: str, options: OptionSequence[T], index: int | None = 0, format_func: Callable[[Any], str] = str, key: Key | None = None, help: str | None = None, on_change: WidgetCallback | None = None, args: WidgetArgs | None = None, kwargs: WidgetKwargs | None = None, *, # keyword-only arguments: placeholder: str | None = None, disabled: bool = False, label_visibility: LabelVisibility = "visible", accept_new_options: bool = False, ) -> T | str | None: r"""Display a select widget. Parameters ---------- label : str A short label explaining to the user what this select widget is for. The label can optionally contain GitHub-flavored Markdown of the following types: Bold, Italics, Strikethroughs, Inline Code, Links, and Images. Images display like icons, with a max height equal to the font height. Unsupported Markdown elements are unwrapped so only their children (text contents) render. Display unsupported elements as literal characters by backslash-escaping them. E.g., ``"1\. Not an ordered list"``. See the ``body`` parameter of |st.markdown|_ for additional, supported Markdown directives. For accessibility reasons, you should never set an empty label, but you can hide it with ``label_visibility`` if needed. In the future, we may disallow empty labels by raising an exception. .. |st.markdown| replace:: ``st.markdown`` .. _st.markdown: https://docs.streamlit.io/develop/api-reference/text/st.markdown options : Iterable Labels for the select options in an ``Iterable``. This can be a ``list``, ``set``, or anything supported by ``st.dataframe``. If ``options`` is dataframe-like, the first column will be used. Each label will be cast to ``str`` internally by default. index : int The index of the preselected option on first render. If ``None``, will initialize empty and return ``None`` until the user selects an option. Defaults to 0 (the first option). format_func : function Function to modify the display of the options. It receives the raw option as an argument and should output the label to be shown for that option. This has no impact on the return value of the command. key : str or int An optional string or integer to use as the unique key for the widget. If this is omitted, a key will be generated for the widget based on its content. No two widgets may have the same key. help : str or None A tooltip that gets displayed next to the widget label. Streamlit only displays the tooltip when ``label_visibility="visible"``. If this is ``None`` (default), no tooltip is displayed. The tooltip can optionally contain GitHub-flavored Markdown, including the Markdown directives described in the ``body`` parameter of ``st.markdown``. on_change : callable An optional callback invoked when this selectbox's value changes. args : tuple An optional tuple of args to pass to the callback. kwargs : dict An optional dict of kwargs to pass to the callback. placeholder : str or None A string to display when no options are selected. If this is ``None`` (default), the widget displays one of the two following placeholder strings: - "Choose an option" is displayed if you set ``accept_new_options=False``. - "Choose or add an option" is displayed if you set ``accept_new_options=True``. disabled : bool An optional boolean that disables the selectbox if set to ``True``. The default is ``False``. label_visibility : "visible", "hidden", or "collapsed" The visibility of the label. The default is ``"visible"``. If this is ``"hidden"``, Streamlit displays an empty spacer instead of the label, which can help keep the widget alligned with other widgets. If this is ``"collapsed"``, Streamlit displays no label or spacer. accept_new_options : bool Whether the user can add a selection that isn't included in ``options``. If this is ``False`` (default), the user can only select from the items in ``options``. If this is ``True``, the user can enter a new item that doesn't exist in ``options``. When a user enters a new item, it is returned by the widget as a string. The new item is not added to the widget's drop-down menu. Streamlit will use a case-insensitive match from ``options`` before adding a new item. Returns ------- any The selected option or ``None`` if no option is selected. Examples -------- **Example 1: Use a basic selectbox widget** If no index is provided, the first option is selected by default. >>> import streamlit as st >>> >>> option = st.selectbox( ... "How would you like to be contacted?", ... ("Email", "Home phone", "Mobile phone"), ... ) >>> >>> st.write("You selected:", option) .. output:: https://doc-selectbox.streamlit.app/ height: 320px **Example 2: Use a selectbox widget with no initial selection** To initialize an empty selectbox, use ``None`` as the index value. >>> import streamlit as st >>> >>> option = st.selectbox( ... "How would you like to be contacted?", ... ("Email", "Home phone", "Mobile phone"), ... index=None, ... placeholder="Select contact method...", ... ) >>> >>> st.write("You selected:", option) .. output:: https://doc-selectbox-empty.streamlit.app/ height: 320px **Example 3: Let users add a new option** To allow users to add a new option that isn't included in the ``options`` list, use the ``accept_new_options=True`` parameter. You can also customize the placeholder text. >>> import streamlit as st >>> >>> option = st.selectbox( ... "Default email", ... ["foo@example.com", "bar@example.com", "baz@example.com"], ... index=None, ... placeholder="Select a saved email or enter a new one", ... accept_new_options=True, ... ) >>> >>> st.write("You selected:", option) .. output:: https://doc-selectbox-accept-new-options.streamlit.app/ height: 320px """ ctx = get_script_run_ctx() return self._selectbox( label=label, options=options, index=index, format_func=format_func, key=key, help=help, on_change=on_change, args=args, kwargs=kwargs, placeholder=placeholder, disabled=disabled, label_visibility=label_visibility, accept_new_options=accept_new_options, ctx=ctx, ) def _selectbox( self, label: str, options: OptionSequence[T], index: int | None = 0, format_func: Callable[[Any], Any] = str, key: Key | None = None, help: str | None = None, on_change: WidgetCallback | None = None, args: WidgetArgs | None = None, kwargs: WidgetKwargs | None = None, *, # keyword-only arguments: placeholder: str | None = None, disabled: bool = False, label_visibility: LabelVisibility = "visible", accept_new_options: bool = False, ctx: ScriptRunContext | None = None, ) -> T | str | None: key = to_key(key) check_widget_policies( self.dg, key, on_change, default_value=None if index == 0 else index, ) maybe_raise_label_warnings(label, label_visibility) opt = convert_anything_to_list(options) check_python_comparable(opt) if not isinstance(index, int) and index is not None: raise StreamlitAPIException( "Selectbox Value has invalid type: %s" % type(index).__name__ ) if index is not None and len(opt) > 0 and not 0 <= index < len(opt): raise StreamlitAPIException( "Selectbox index must be greater than or equal to 0 " "and less than the length of options." ) if placeholder is None: placeholder = ( "Choose an option" if not accept_new_options else "Choose or add an option" ) formatted_options, formatted_option_to_option_index = create_mappings( opt, format_func ) element_id = compute_and_register_element_id( "selectbox", user_key=key, form_id=current_form_id(self.dg), label=label, options=formatted_options, index=index, help=help, placeholder=placeholder, accept_new_options=accept_new_options, ) session_state = get_session_state().filtered_state if key is not None and key in session_state and session_state[key] is None: index = None selectbox_proto = SelectboxProto() selectbox_proto.id = element_id selectbox_proto.label = label if index is not None: selectbox_proto.default = index selectbox_proto.options[:] = formatted_options selectbox_proto.form_id = current_form_id(self.dg) selectbox_proto.placeholder = placeholder selectbox_proto.disabled = disabled selectbox_proto.label_visibility.value = get_label_visibility_proto_value( label_visibility ) selectbox_proto.accept_new_options = accept_new_options if help is not None: selectbox_proto.help = dedent(help) serde = SelectboxSerde( opt, formatted_options=formatted_options, formatted_option_to_option_index=formatted_option_to_option_index, default_option_index=index, ) widget_state = register_widget( selectbox_proto.id, on_change_handler=on_change, args=args, kwargs=kwargs, deserializer=serde.deserialize, serializer=serde.serialize, ctx=ctx, value_type="string_value", ) widget_state = maybe_coerce_enum(widget_state, options, opt) if widget_state.value_changed: serialized_value = serde.serialize(widget_state.value) if serialized_value is not None: selectbox_proto.raw_value = serialized_value selectbox_proto.set_value = True if ctx: save_for_app_testing(ctx, element_id, format_func) self.dg._enqueue("selectbox", selectbox_proto) return widget_state.value @property def dg(self) -> DeltaGenerator: """Get our DeltaGenerator.""" return cast("DeltaGenerator", self)