napari 0.4.2

We’re happy to announce the release of napari 0.4.2! napari is a fast, interactive, multi-dimensional image viewer for Python. It’s designed for browsing, annotating, and analyzing large multi-dimensional images. It’s built on top of Qt (for the GUI), vispy (for performant GPU-based rendering), and the scientific Python stack (numpy, scipy).

For more information, examples, and documentation, please visit our website:


This is an emergency patch release to fix a regression in 0.4.1 that broke magicgui generated dockwidgets which accepted layers as input (#1962). The release also contains a number of other bug fixes and improvements, notably a fix to a performance regression when adding many layers that came in the 0.3.6 release (#1945), and the beginning of adopting evented dataclasses for our model files, which will result in a dramatic simplification of that part of the codebase.


  • async-28: Misc Cleanup (#1900)

  • async-29: Shared Memory Server (#1909)

  • Use evented dataclass for axes (#1910)

  • Use evented dataclass for scalebar (#1911)

  • Use evented dataclass for cursor (#1912)

  • Use evented dataclass for grid (#1913)

  • Use evented dataclass for camera (#1914)

  • Use evented dataclass for colormap (#1916)

  • Remove add layers mixin (#1921)

Bug Fixes

  • Fix performance issues 1 - adding layers (#1945)

  • Fix track labels lookup (#1946)

  • Update sliders when change scale of layer (#1951)

  • Fix evented dataclass for python 3.9 (#1958)

  • Refine TypedMutableSequence.getitem error type, add magicgui tests (#1962)

API Changes

  • has been dropped. Instead, use Viewer.dims.ndisplay. (#1914)


  • All existing deprecations have been bumped by one release (#1963)

Build Tools and Docs

  • Fix checks for running under cProfile and yappi (#1924)

  • Fix missing vispy.ext.six (#1930)

  • Replace calls to layer.shape in tests (#1938)

  • Add pims to bundle (#1939)

  • Register sync_only pytest mark to fix warning (#1941)

  • Don’t run app bundling in forked repos (#1953)

  • Add tests for #1895 (#1961)

8 authors added to this release (alphabetical)

5 reviewers added to this release (alphabetical)