Transfer

Introduction

The Transfer widget in Supervisely is a user interface element that allows users to transfer items between two lists. The Transfer widget is useful for creating project dashboards that require users to transfer items between two lists quickly and easily. Users can customize the appearance and behavior of the Transfer widget to match their project requirements, such as adding filterable options and customizing the names of the lists, buttons, and more. Overall, the Transfer widget is a simple tool to select needed or remove unnecessary items from the list. The Transfer widget has event handlers that are triggered when items in the right lists are changed. This can be useful for applications that require dynamic change handling, such as showing data from the selected items.

Read this tutorial in the developer portal.

Function signature

Transfer(
    items=None, transferred_items=None,
    filterable=False, filter_placeholder=None,
    titles=None, button_texts=None,
    left_checked=None, right_checked=None,
    widget_id=None
)

default

Parameters

Parameters	Type	Description
items	Union[List[Item], List[str]]	List of Transfer.Item widgets or list of strings
transferred_items	List[str]	List of strings, containing keys from items
filterable	bool	Whether Transfer is filterable
filter_placeholder	str	Placeholder for filter if filterable=True
titles	List[str	List of titles for left and right lists
button_texts	List[str	List of button texts for left and right lists
left_checked	List[str	List of checked items for left list
right_checked	List[str	List of checked items for right list
widget_id	str	ID of the widget

items

Determine the list of Transfer.Item widgets or list of strings, containing keys for items, from which Transfer.Item widgets will be created.

type: Union[List[Item], List[str]]

default value: None

Prepare transfer items:

animals_domestic = [
    Transfer.Item(key="cat", label="Cat", disabled=True),
    Transfer.Item(key="dog", label="Dog"),
]
animals_wild = [
    Transfer.Item(key="mouse"),
]

Initialize widget with given items:

transfer = Transfer(
    items=animals_domestic + animals_wild,
)

items

transferred_items

Determine the list of strings, containing keys for items, that will be shown in the right list. Note: transferred_items should be a subset of keys of items, otherwise the error will be raised.

type: List[str]

default value: None

Initialize widget with transferred items:

transfer = Transfer(
    items=animals_domestic + animals_wild,
    transferred_items=["dog"],
)

transferred_items

filterable

Determine whether the Transfer is filterable or not.

type: bool

default value: False

Initialize widget with filterable option:

transfer = Transfer(
    items=animals_domestic + animals_wild,
    filterable=True,
)

filterable

filter_placeholder

Determine the placeholder for the filter field if filterable=True.

type: str

default value: None

Initialize widget with filter placeholder:

transfer = Transfer(
    items=animals_domestic + animals_wild,
    filterable=True,
    filter_placeholder="Filter animals",
)

filter_placeholder

titles

Determine the list of titles for left and right lists.

type: List[str]

default value: None

Initialize widget with titles:

transfer = Transfer(
    items=animals_domestic + animals_wild,
    titles=["Domestic animals", "Wild animals"],
)

titles

button_texts

Determine the list of texts for each button.

type: List[str]

default value: None

Initialize widget with button texts:

transfer = Transfer(
    items=animals_domestic + animals_wild,
    button_texts=["Remove", "Add"],
)

button_texts

left_checked

Determine the list of items that will be checked in the left list when the widget is initialized.

type: List[str]

default value: None

Initialize widget with checked items:

transfer = Transfer(
    items=animals_domestic + animals_wild,
    left_checked=["dog"],
)

left_checked

right_checked

Determine the list of items that will be checked in the right list when the widget is initialized.

type: List[str]

default value: None

Initialize widget with checked items:

transfer = Transfer(
    items=animals_domestic + animals_wild,
    transferred_items=["dog"],
    right_checked=["dog"],
)

right_checked

widget_id

The ID of the widget.

type: str

default value: None

Initialize widget with ID:

transfer = Transfer(
    items=animals_domestic + animals_wild,
    widget_id="transfer",
)

Methods and attributes

Methods and attributes	Description
get_transferred_items()	Get the list of keys of items in the right list
get_untransferred_items()	Get the list of keys of items in the left list
@value_changed	Event that is triggered when items in the right list changed
set_items(items: Union[List[Transfer.Item], List[str]])	Set the items list (replacing it) for the widget
set_transferred_items(transferred_items: List[str])	Set the transferred items list (replacing it) for the widget
add(items: Union[List[Item], List[str]]):	Adds new items to the widget
remove(items_keys: List[str])	Remove items from the widget by key
get_items_keys()	Get the list of keys of items in the widget

Mini app example

You can find this example in our GitHub repository:

supervisely-ecosystem/ui-widgets-demos/selection/010_transfer/src/main.py

Import libraries

import os

import supervisely as sly
from dotenv import load_dotenv
from supervisely.app.widgets import Card, Transfer, Container, Text

Init API client

First, we load environment variables with credentials and init API for communicating with Supervisely Instance:

load_dotenv("local.env")
load_dotenv(os.path.expanduser("~/supervisely.env"))

api = sly.Api()

Prepare items for Transfer widget

# Preparing list of items as Transfer.Item objects.
domestic_animals = [
    Transfer.Item(key="cat", label="Cat", disabled=True),
    Transfer.Item(key="dog"),
    Transfer.Item(key="cow"),
    Transfer.Item(key="sheep"),
]
# Preparing list of items as strings, which will be converted to Transfer.Item objects.
wild_animals = ["mouse", "bird"]

Initialize Transfer widget

# Initializing Transfer widget with first list of items.
transfer = Transfer(
    # List of all items for the widget (both left and right).
    items=domestic_animals,
    # List of items that will in the right list when the widget is initialized.
    transferred_items=["cat", "cow"],
    # Making the widget lists filterable.
    filterable=True,
    # Setting the placeholder for the filter input.
    filter_placeholder="Search...",
    # Setting the title for the both lists.
    titles=["Available", "Transferred"],
    # Setting the names for the buttons.
    button_texts=["Remove", "Add"],
    # Setting the items which will be checked in the left list when the widget is initialized.
    left_checked=["dog"],
    # Setting the items which will be checked in the right list when the widget is initialized.
    right_checked=["cow"],
)
# Adding new items to the widget.
transfer.add(wild_animals)

Changing the list of transferred items

# Updating the transferred items, which will be shown in the right list.
# Note: if you want to ADD items (not REPLACE them), don't forget to pass the old transferred items to the method.
transfer.set_transferred_items(transfer.get_transferred_items() + ["mouse"])

Removing an item and getting keys of items (all, transferred, untransferred)

# Printing the keys of items in the left list.
print("Keys of items in the left list ", transfer.get_untransferred_items())
# Printing the keys of items in the right list.
print("Keys of items in the right list ", transfer.get_transferred_items())

# Removing item from widget by its key.
transfer.remove(["sheep"])

# Printing the keys of all items in the widget.
print("Keys of all items in the widget ", transfer.get_items_keys())

Using @value_changed event

# Preparing text widget to show the message about the value change.
value_changed_message = Text(status="info")


# Creating decorated function to show the current state of the widget.
@transfer.value_changed
def show_message_with_keys(Items):
    # The Items object is a named tuple containing two lists:
    # keys of items in the left list and keys of items in the right list.
    value_changed_message.text = (
        f"Left list: {Items.untransferred_items}. Right list: {Items.transferred_items}."
    )

Create app layout

Prepare a layout for the app using Card widget with the content parameter and place widget that we've just created in the Container widget.

# Creating Card widget, which will contain the Transfer widget and the Text widget.
card = Card(title="Transfer", content=Container(widgets=[transfer, value_changed_message]))
# Creating the application layout.
layout = Container(widgets=[card])

Create an app using the layout

Create an app object with the layout parameter.

# Initializing the application.
app = sly.Application(layout=layout)

mini_app