Small error in docstring of matplotlib.colors.from_levels_and_colors

Lines 2708 to 2762 in 3958242

    
           def from_levels_and_colors(levels, colors, extend='neither'): 
        
               """ 
        
               A helper routine to generate a cmap and a norm instance which 
        
               behave similar to contourf's levels and colors arguments. 
        
               Parameters 
        
               ---------- 
        
               levels : sequence of numbers 
        
                   The quantization levels used to construct the `BoundaryNorm`. 
        
                   Value ``v`` is quantized to level ``i`` if ``lev[i] <= v < lev[i+1]``. 
        
               colors : sequence of colors 
        
                   The fill color to use for each level. If *extend* is "neither" there 
        
                   must be ``n_level - 1`` colors. For an *extend* of "min" or "max" add 
        
                   one extra color, and for an *extend* of "both" add two colors. 
        
               extend : {'neither', 'min', 'max', 'both'}, optional 
        
                   The behaviour when a value falls out of range of the given levels. 
        
                   See `~.Axes.contourf` for details. 
        
               Returns 
        
               ------- 
        
               cmap : `~matplotlib.colors.Normalize` 
        
               norm : `~matplotlib.colors.Colormap` 
        
               """ 
        
               slice_map = { 
        
                   'both': slice(1, -1), 
        
                   'min': slice(1, None), 
        
                   'max': slice(0, -1), 
        
                   'neither': slice(0, None), 
        
               } 
        
               _api.check_in_list(slice_map, extend=extend) 
        
               color_slice = slice_map[extend] 
        
               n_data_colors = len(levels) - 1 
        
               n_expected = n_data_colors + color_slice.start - (color_slice.stop or 0) 
        
               if len(colors) != n_expected: 
        
                   raise ValueError( 
        
                       f'With extend == {extend!r} and {len(levels)} levels, ' 
        
                       f'expected {n_expected} colors, but got {len(colors)}') 
        
               cmap = ListedColormap(colors[color_slice], N=n_data_colors) 
        
               if extend in ['min', 'both']: 
        
                   cmap.set_under(colors[0]) 
        
               else: 
        
                   cmap.set_under('none') 
        
               if extend in ['max', 'both']: 
        
                   cmap.set_over(colors[-1]) 
        
               else: 
        
                   cmap.set_over('none') 
        
               cmap.colorbar_extend = extend 
        
               norm = BoundaryNorm(levels, ncolors=n_data_colors) 
        
               return cmap, norm

The docstring of matplotlib.colors.from_levels_and_colors states that the function returns:

    cmap : `~matplotlib.colors.Normalize`
    norm : `~matplotlib.colors.Colormap`

while the code confirms that, as expected, it's the opposite that is returned (cmap is a Colormap and norm is a Normalize)

@glthm

Good spot @glthm! Are you interested in making a pull request to correct it?

Good first issue - notes for new contributors

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someone was faster than me, my first pull request won't be for today, maybe next time

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Small error in docstring of matplotlib.colors.from_levels_and_colors #27188

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	def from_levels_and_colors(levels, colors, extend='neither'):
	"""
	A helper routine to generate a cmap and a norm instance which
	behave similar to contourf's levels and colors arguments.

	Parameters
	----------
	levels : sequence of numbers
	The quantization levels used to construct the `BoundaryNorm`.
	Value ``v`` is quantized to level ``i`` if ``lev[i] <= v < lev[i+1]``.
	colors : sequence of colors
	The fill color to use for each level. If extend is "neither" there
	must be ``n_level - 1`` colors. For an extend of "min" or "max" add
	one extra color, and for an extend of "both" add two colors.
	extend : {'neither', 'min', 'max', 'both'}, optional
	The behaviour when a value falls out of range of the given levels.
	See `~.Axes.contourf` for details.

	Returns
	-------
	cmap : `~matplotlib.colors.Normalize`
	norm : `~matplotlib.colors.Colormap`
	"""
	slice_map = {
	'both': slice(1, -1),
	'min': slice(1, None),
	'max': slice(0, -1),
	'neither': slice(0, None),
	}
	_api.check_in_list(slice_map, extend=extend)
	color_slice = slice_map[extend]

	n_data_colors = len(levels) - 1
	n_expected = n_data_colors + color_slice.start - (color_slice.stop or 0)
	if len(colors) != n_expected:
	raise ValueError(
	f'With extend == {extend!r} and {len(levels)} levels, '
	f'expected {n_expected} colors, but got {len(colors)}')

	cmap = ListedColormap(colors[color_slice], N=n_data_colors)

	if extend in ['min', 'both']:
	cmap.set_under(colors[0])
	else:
	cmap.set_under('none')

	if extend in ['max', 'both']:
	cmap.set_over(colors[-1])
	else:
	cmap.set_over('none')

	cmap.colorbar_extend = extend

	norm = BoundaryNorm(levels, ncolors=n_data_colors)
	return cmap, norm

Small error in docstring of matplotlib.colors.from_levels_and_colors #27188

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rcomer commented on Oct 25, 2023

github-actions commented on Oct 25, 2023

Good first issue - notes for new contributors

glthm commented on Oct 26, 2023

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