"plt.savefig“现在会引发一个TypeError

Question

我有一个代码，它曾经运行得很好。但是，它现在会引发错误

TypeError: object of type 'NoneType' has no len()

在行plt.savefig中。我使用Jupyter笔记本(通过Anaconda)。

更新:问题出在"ax.legend“上。当它被注释时，代码就会运行。

我找了here，但找不到解决方案。

代码：

import matplotlib.pyplot as plt
.
.
.

plt.rc('xtick', labelsize=18) 
plt.rc('ytick', labelsize=18)

fig, ax = plt.subplots(figsize=(15,15))
for label,color,shape,inds in zip(labels,colors,shapes,indss):
    ax.scatter(pca_coor[inds, 0], pca_coor[inds, 1], c=color, 
               label=label, s=150, marker=shape)
ax.legend(labels, prop={'size': 20})
ax.set_title('title',fontdict={'fontsize': 30, 'fontweight': 'medium'})
ax.set_xlabel('PC 1', fontdict={'fontsize': 22, 'fontweight': 'medium'})
ax.set_ylabel('PC 2', fontdict={'fontsize': 22, 'fontweight': 'medium'})

# save the figure to file
plt.savefig('picfile.png')
plt.close()

这就是整个错误：

-> 2486                 plt.savefig('picfile.png')
   2487                 #plt.clf()
   2488                 plt.close()

~\Anaconda3\lib\site-packages\matplotlib\pyplot.py in savefig(*args, **kwargs)
    935 def savefig(*args, **kwargs):
    936     fig = gcf()
--> 937     res = fig.savefig(*args, **kwargs)
    938     fig.canvas.draw_idle()   # need this if 'transparent=True' to reset colors
    939     return res

~\Anaconda3\lib\site-packages\matplotlib\figure.py in savefig(self, fname, transparent, **kwargs)
   2957                 patch.set_edgecolor('none')
   2958 
-> 2959         self.canvas.print_figure(fname, **kwargs)
   2960 
   2961         if transparent:

~\Anaconda3\lib\site-packages\matplotlib\backend_bases.py in print_figure(self, filename, dpi, facecolor, edgecolor, orientation, format, bbox_inches, pad_inches, bbox_extra_artists, backend, **kwargs)
   2259                         orientation=orientation,
   2260                         bbox_inches_restore=_bbox_inches_restore,
-> 2261                         **kwargs)
   2262             finally:
   2263                 if bbox_inches and restore_bbox:

~\Anaconda3\lib\site-packages\matplotlib\backend_bases.py in wrapper(*args, **kwargs)
   1667             kwargs.pop(arg)
   1668 
-> 1669         return func(*args, **kwargs)
   1670 
   1671     return wrapper

~\Anaconda3\lib\site-packages\matplotlib\backends\backend_agg.py in print_png(self, filename_or_obj, metadata, pil_kwargs, *args)
    506             *metadata*, including the default 'Software' key.
    507         """
--> 508         FigureCanvasAgg.draw(self)
    509         mpl.image.imsave(
    510             filename_or_obj, self.buffer_rgba(), format="png", origin="upper",

~\Anaconda3\lib\site-packages\matplotlib\backends\backend_agg.py in draw(self)
    404              (self.toolbar._wait_cursor_for_draw_cm() if self.toolbar
    405               else nullcontext()):
--> 406             self.figure.draw(self.renderer)
    407             # A GUI class may be need to update a window using this draw, so
    408             # don't forget to call the superclass.

~\Anaconda3\lib\site-packages\matplotlib\artist.py in draw_wrapper(artist, renderer, *args, **kwargs)
     72     @wraps(draw)
     73     def draw_wrapper(artist, renderer, *args, **kwargs):
---> 74         result = draw(artist, renderer, *args, **kwargs)
     75         if renderer._rasterizing:
     76             renderer.stop_rasterizing()

~\Anaconda3\lib\site-packages\matplotlib\artist.py in draw_wrapper(artist, renderer, *args, **kwargs)
     49                 renderer.start_filter()
     50 
---> 51             return draw(artist, renderer, *args, **kwargs)
     52         finally:
     53             if artist.get_agg_filter() is not None:

~\Anaconda3\lib\site-packages\matplotlib\figure.py in draw(self, renderer)
   2733             self.patch.draw(renderer)
   2734             mimage._draw_list_compositing_images(
-> 2735                 renderer, self, artists, self.suppressComposite)
   2736 
   2737             for sfig in self.subfigs:

~\Anaconda3\lib\site-packages\matplotlib\image.py in _draw_list_compositing_images(renderer, parent, artists, suppress_composite)
    130     if not_composite or not has_images:
    131         for a in artists:
--> 132             a.draw(renderer)
    133     else:
    134         # Composite any adjacent images together

~\Anaconda3\lib\site-packages\matplotlib\artist.py in draw_wrapper(artist, renderer, *args, **kwargs)
     49                 renderer.start_filter()
     50 
---> 51             return draw(artist, renderer, *args, **kwargs)
     52         finally:
     53             if artist.get_agg_filter() is not None:

~\Anaconda3\lib\site-packages\matplotlib\_api\deprecation.py in wrapper(*inner_args, **inner_kwargs)
    429                          else deprecation_addendum,
    430                 **kwargs)
--> 431         return func(*inner_args, **inner_kwargs)
    432 
    433     return wrapper

~\Anaconda3\lib\site-packages\matplotlib\axes\_base.py in draw(self, renderer, inframe)
   2923             renderer.stop_rasterizing()
   2924 
-> 2925         mimage._draw_list_compositing_images(renderer, self, artists)
   2926 
   2927         renderer.close_group('axes')

~\Anaconda3\lib\site-packages\matplotlib\image.py in _draw_list_compositing_images(renderer, parent, artists, suppress_composite)
    130     if not_composite or not has_images:
    131         for a in artists:
--> 132             a.draw(renderer)
    133     else:
    134         # Composite any adjacent images together

~\Anaconda3\lib\site-packages\matplotlib\artist.py in draw_wrapper(artist, renderer, *args, **kwargs)
     49                 renderer.start_filter()
     50 
---> 51             return draw(artist, renderer, *args, **kwargs)
     52         finally:
     53             if artist.get_agg_filter() is not None:

~\Anaconda3\lib\site-packages\matplotlib\legend.py in draw(self, renderer)
    612 
    613         self.legendPatch.draw(renderer)
--> 614         self._legend_box.draw(renderer)
    615 
    616         renderer.close_group('legend')

~\Anaconda3\lib\site-packages\matplotlib\offsetbox.py in draw(self, renderer)
    366         for c, (ox, oy) in zip(self.get_visible_children(), offsets):
    367             c.set_offset((px + ox, py + oy))
--> 368             c.draw(renderer)
    369 
    370         bbox_artist(self, renderer, fill=False, props=dict(pad=0.))

~\Anaconda3\lib\site-packages\matplotlib\offsetbox.py in draw(self, renderer)
    366         for c, (ox, oy) in zip(self.get_visible_children(), offsets):
    367             c.set_offset((px + ox, py + oy))
--> 368             c.draw(renderer)
    369 
    370         bbox_artist(self, renderer, fill=False, props=dict(pad=0.))

~\Anaconda3\lib\site-packages\matplotlib\offsetbox.py in draw(self, renderer)
    366         for c, (ox, oy) in zip(self.get_visible_children(), offsets):
    367             c.set_offset((px + ox, py + oy))
--> 368             c.draw(renderer)
    369 
    370         bbox_artist(self, renderer, fill=False, props=dict(pad=0.))

~\Anaconda3\lib\site-packages\matplotlib\offsetbox.py in draw(self, renderer)
    366         for c, (ox, oy) in zip(self.get_visible_children(), offsets):
    367             c.set_offset((px + ox, py + oy))
--> 368             c.draw(renderer)
    369 
    370         bbox_artist(self, renderer, fill=False, props=dict(pad=0.))

~\Anaconda3\lib\site-packages\matplotlib\offsetbox.py in draw(self, renderer)
    692             if self._clip_children and not (c.clipbox or c._clippath):
    693                 c.set_clip_path(tpath)
--> 694             c.draw(renderer)
    695 
    696         bbox_artist(self, renderer, fill=False, props=dict(pad=0.))

~\Anaconda3\lib\site-packages\matplotlib\artist.py in draw_wrapper(artist, renderer, *args, **kwargs)
     49                 renderer.start_filter()
     50 
---> 51             return draw(artist, renderer, *args, **kwargs)
     52         finally:
     53             if artist.get_agg_filter() is not None:

~\Anaconda3\lib\site-packages\matplotlib\collections.py in draw(self, renderer)
   1007     def draw(self, renderer):
   1008         self.set_sizes(self._sizes, self.figure.dpi)
-> 1009         super().draw(renderer)
   1010 
   1011 

~\Anaconda3\lib\site-packages\matplotlib\artist.py in draw_wrapper(artist, renderer, *args, **kwargs)
     49                 renderer.start_filter()
     50 
---> 51             return draw(artist, renderer, *args, **kwargs)
     52         finally:
     53             if artist.get_agg_filter() is not None:

~\Anaconda3\lib\site-packages\matplotlib\collections.py in draw(self, renderer)
    378         do_single_path_optimization = False
    379         if (len(paths) == 1 and len(trans) <= 1 and
--> 380                 len(facecolors) == 1 and len(edgecolors) == 1 and
    381                 len(self._linewidths) == 1 and
    382                 all(ls[1] is None for ls in self._linestyles) and

TypeError: object of type 'NoneType' has no len()

---------------------------------------------------------------------------
TypeError                                 Traceback (most recent call last)
~\Anaconda3\lib\site-packages\IPython\core\formatters.py in __call__(self, obj)
    339                 pass
    340             else:
--> 341                 return printer(obj)
    342             # Finally look for special method names
    343             method = get_real_method(obj, self.print_method)

~\Anaconda3\lib\site-packages\IPython\core\pylabtools.py in <lambda>(fig)
    246 
    247     if 'png' in formats:
--> 248         png_formatter.for_type(Figure, lambda fig: print_figure(fig, 'png', **kwargs))
    249     if 'retina' in formats or 'png2x' in formats:
    250         png_formatter.for_type(Figure, lambda fig: retina_figure(fig, **kwargs))

~\Anaconda3\lib\site-packages\IPython\core\pylabtools.py in print_figure(fig, fmt, bbox_inches, **kwargs)
    130         FigureCanvasBase(fig)
    131 
--> 132     fig.canvas.print_figure(bytes_io, **kw)
    133     data = bytes_io.getvalue()
    134     if fmt == 'svg':

~\Anaconda3\lib\site-packages\matplotlib\backend_bases.py in print_figure(self, filename, dpi, facecolor, edgecolor, orientation, format, bbox_inches, pad_inches, bbox_extra_artists, backend, **kwargs)
   2228                        else suppress())
   2229                 with ctx:
-> 2230                     self.figure.draw(renderer)
   2231 
   2232             if bbox_inches:

~\Anaconda3\lib\site-packages\matplotlib\artist.py in draw_wrapper(artist, renderer, *args, **kwargs)
     72     @wraps(draw)
     73     def draw_wrapper(artist, renderer, *args, **kwargs):
---> 74         result = draw(artist, renderer, *args, **kwargs)
     75         if renderer._rasterizing:
     76             renderer.stop_rasterizing()

~\Anaconda3\lib\site-packages\matplotlib\artist.py in draw_wrapper(artist, renderer, *args, **kwargs)
     49                 renderer.start_filter()
     50 
---> 51             return draw(artist, renderer, *args, **kwargs)
     52         finally:
     53             if artist.get_agg_filter() is not None:

~\Anaconda3\lib\site-packages\matplotlib\figure.py in draw(self, renderer)
   2733             self.patch.draw(renderer)
   2734             mimage._draw_list_compositing_images(
-> 2735                 renderer, self, artists, self.suppressComposite)
   2736 
   2737             for sfig in self.subfigs:

~\Anaconda3\lib\site-packages\matplotlib\image.py in _draw_list_compositing_images(renderer, parent, artists, suppress_composite)
    130     if not_composite or not has_images:
    131         for a in artists:
--> 132             a.draw(renderer)
    133     else:
    134         # Composite any adjacent images together

~\Anaconda3\lib\site-packages\matplotlib\artist.py in draw_wrapper(artist, renderer, *args, **kwargs)
     49                 renderer.start_filter()
     50 
---> 51             return draw(artist, renderer, *args, **kwargs)
     52         finally:
     53             if artist.get_agg_filter() is not None:

~\Anaconda3\lib\site-packages\matplotlib\_api\deprecation.py in wrapper(*inner_args, **inner_kwargs)
    429                          else deprecation_addendum,
    430                 **kwargs)
--> 431         return func(*inner_args, **inner_kwargs)
    432 
    433     return wrapper

~\Anaconda3\lib\site-packages\matplotlib\axes\_base.py in draw(self, renderer, inframe)
   2923             renderer.stop_rasterizing()
   2924 
-> 2925         mimage._draw_list_compositing_images(renderer, self, artists)
   2926 
   2927         renderer.close_group('axes')

~\Anaconda3\lib\site-packages\matplotlib\image.py in _draw_list_compositing_images(renderer, parent, artists, suppress_composite)
    130     if not_composite or not has_images:
    131         for a in artists:
--> 132             a.draw(renderer)
    133     else:
    134         # Composite any adjacent images together

~\Anaconda3\lib\site-packages\matplotlib\artist.py in draw_wrapper(artist, renderer, *args, **kwargs)
     49                 renderer.start_filter()
     50 
---> 51             return draw(artist, renderer, *args, **kwargs)
     52         finally:
     53             if artist.get_agg_filter() is not None:

~\Anaconda3\lib\site-packages\matplotlib\legend.py in draw(self, renderer)
    612 
    613         self.legendPatch.draw(renderer)
--> 614         self._legend_box.draw(renderer)
    615 
    616         renderer.close_group('legend')

~\Anaconda3\lib\site-packages\matplotlib\offsetbox.py in draw(self, renderer)
    366         for c, (ox, oy) in zip(self.get_visible_children(), offsets):
    367             c.set_offset((px + ox, py + oy))
--> 368             c.draw(renderer)
    369 
    370         bbox_artist(self, renderer, fill=False, props=dict(pad=0.))

~\Anaconda3\lib\site-packages\matplotlib\offsetbox.py in draw(self, renderer)
    366         for c, (ox, oy) in zip(self.get_visible_children(), offsets):
    367             c.set_offset((px + ox, py + oy))
--> 368             c.draw(renderer)
    369 
    370         bbox_artist(self, renderer, fill=False, props=dict(pad=0.))

~\Anaconda3\lib\site-packages\matplotlib\offsetbox.py in draw(self, renderer)
    366         for c, (ox, oy) in zip(self.get_visible_children(), offsets):
    367             c.set_offset((px + ox, py + oy))
--> 368             c.draw(renderer)
    369 
    370         bbox_artist(self, renderer, fill=False, props=dict(pad=0.))

~\Anaconda3\lib\site-packages\matplotlib\offsetbox.py in draw(self, renderer)
    366         for c, (ox, oy) in zip(self.get_visible_children(), offsets):
    367             c.set_offset((px + ox, py + oy))
--> 368             c.draw(renderer)
    369 
    370         bbox_artist(self, renderer, fill=False, props=dict(pad=0.))

~\Anaconda3\lib\site-packages\matplotlib\offsetbox.py in draw(self, renderer)
    692             if self._clip_children and not (c.clipbox or c._clippath):
    693                 c.set_clip_path(tpath)
--> 694             c.draw(renderer)
    695 
    696         bbox_artist(self, renderer, fill=False, props=dict(pad=0.))

~\Anaconda3\lib\site-packages\matplotlib\artist.py in draw_wrapper(artist, renderer, *args, **kwargs)
     49                 renderer.start_filter()
     50 
---> 51             return draw(artist, renderer, *args, **kwargs)
     52         finally:
     53             if artist.get_agg_filter() is not None:

~\Anaconda3\lib\site-packages\matplotlib\collections.py in draw(self, renderer)
   1007     def draw(self, renderer):
   1008         self.set_sizes(self._sizes, self.figure.dpi)
-> 1009         super().draw(renderer)
   1010 
   1011 

~\Anaconda3\lib\site-packages\matplotlib\artist.py in draw_wrapper(artist, renderer, *args, **kwargs)
     49                 renderer.start_filter()
     50 
---> 51             return draw(artist, renderer, *args, **kwargs)
     52         finally:
     53             if artist.get_agg_filter() is not None:

~\Anaconda3\lib\site-packages\matplotlib\collections.py in draw(self, renderer)
    378         do_single_path_optimization = False
    379         if (len(paths) == 1 and len(trans) <= 1 and
--> 380                 len(facecolors) == 1 and len(edgecolors) == 1 and
    381                 len(self._linewidths) == 1 and
    382                 all(ls[1] is None for ls in self._linestyles) and

TypeError: object of type 'NoneType' has no len()

<Figure size 1080x1080 with 1 Axes>

matplotlib版本: 3.4.0

提前谢谢。

Answer 1

我设法解决了这个问题，将ax.scatter中的"c“改为"color”，并从ax.legend中删除了"labels“。