[scikit-image] ValueError: too many values to unpack for measure.marching_cubes

[Egor Panfilov]

Hi,

Functions in Python return objects packed in a tuple. When you write
`verts, faces = marching_cubes(...)`, Python computes
`marching_cubes(...)`, takes the output, and tries to unpack it (i.e. to
assign to the names on the left-hand side of `=`) to 2 objects. The error
tells you that the number of objects in a returned tuple is too high (>2).

Here is an example to better understand the issue:

In [1]: a, b = (1, 2)
In [2]: a, b, c = (1, 2)
---------------------------------------------------------------------------
ValueError                                Traceback (most recent call last)
<ipython-input-5-26c544669ffc> in <module>()
----> 1 a, b, c = (1, 2)

ValueError: not enough values to unpack (expected 3, got 2)

In [3]: a, b = (1, 2, 3)
---------------------------------------------------------------------------
ValueError                                Traceback (most recent call last)
<ipython-input-6-2ecd6d570722> in <module>()
----> 1 a, b = (1, 2, 3)

ValueError: too many values to unpack (expected 2)


In skimage 0.13, as far as I remember, `marching_cubes` is actually an
alias to `marching_cubes_lewiner` (
http://scikit-image.org/docs/dev/api/skimage.measure.html#skimage.measure.marching_cubes_lewiner)
which returns 4 objects, not 2. In skimage 0.14dev we've already removed
this alias.
You should either use `marching_cubes_classic` (not recommended), or update
your code to use `marching_cubes_lewiner` and unpack the output to 4
variables.

Regards,
Egor

2017-08-07 17:16 GMT+03:00 wine lover <winecoding at gmail.com>:

> Hello,
>
> I have been trying to follow the tutorial here https://www.kaggle.com/
> gzuidhof/full-preprocessing-tutorial
>
> However, verts, faces, , = measure.marching_cubes(p, threshold) in the
> function of plot_3d gives the following error message
>
>  File "guidozuidhof_fullprocessing.py", line 90, in plot_3d
>     verts, faces = measure.marching_cubes(p, threshold)
> ValueError: too many values to unpack
>
>
> What does that mean, and how to solve it, thanks a lot!
>
> _______________________________________________
> scikit-image mailing list
> scikit-image at python.org
> https://mail.python.org/mailman/listinfo/scikit-image
>
>
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