A set of widgets to help facilitate reuse of large datasets across widgets
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ipydatawidgets is a set of widgets to help facilitate reuse of large datasets across different widgets, and different packages.


A typical installation requires the following three commands to be run:

pip install ipydatawidgets
jupyter nbextension install --py [--sys-prefix|--user|--system] ipydatawidgets
jupyter nbextension enable --py [--sys-prefix|--user|--system] ipydatawidgets

Or, if you use jupyterlab:

pip install ipydatawidgets
jupyter labextension install jupyterlab-datawidgets


As a user, it should be noted that ipydatawidgets only works with packages that explicitly allow for it, so a more detailed usage guide might be available in the documentation of those packages. If you are a developer who wants to add support for data widgets in your package, read the developer's section further below.


The main widget for arrays is the NDArrayWidget class. It has a main trait: A numpy array. This array can be constrained/coerced in both size/shape and in data type. It's main purpose is simply to be a standardized way of transmitting array data from the kernel to the frontend, and to allow the data to be reused across any number of other widgets, but with only a single sync across the network.

import numpy as np
from ipydatawidgets import NDArrayWidget

raw_data = np.ones((100, 100, 3), dtype=np.float32)
datawidget = NDArrayWidget(raw_data)

# Below, my_other_widget has a trait `data` of the type `Instance(NDArrayWidget)`
my_other_widget.data = datawidget

In addition to the NDArrayWidget, ipydatawidgets also expose the trait type for the numpy array and its serializers (on both the Python side and the javascript side). More importantly, it exposes a DataUnion trait type, that accepts both numpy arrays directly, or a reference to an NDArrayWidget. This allows other widgets to easily accept either a numpy array or a data widget. Then the user can choose which one they prefer, weighing the pros and cons against eachother (the con of the widget being the extra overhead of creation).

# ... continuation of example above
my_other_widget.data = raw_data  # also acceptable, if `data` is a DataUnion


Developers should consider using ipydatawidgets because:

  • It gives readily accessible syncing of array data using the binary transfer protocol of ipywidgets.
  • It has inbuilt mechanisms for constraining shape and dtype, and can quickly be extended with more complex constraints.
  • It avoids duplication of common code among different extensions, ensuring that bugs discovered for one extension gets fixed in all.


The major parts of ipydatawidgets are:

  • Traits/Widgets definitions
  • Validators to coerce/constrain values assigned to those traits
  • Serializers/deserializers to send the data across the network
  • Apropriate javascript handling and representation of the data