具有散点图和标签的TypeError

Question

这看起来很简单，但由于某些原因，我不能让它工作。这是在pandas 1.2.3和matplotlib 3.4.0中运行的，运行在本地Jupyter笔记本中的Windows1064位anaconda的python 3.8.8上。

我已经在下面创建了一个副本。首先，是一个工作版本；注意注释掉的标签行：

import numpy as np
import pandas as pd
import matplotlib.pyplot as plt

df_test = pd.DataFrame(np.random.randn(1000, 4), columns=list("ABCD"))

df_test.plot(kind="scatter", x="A", y="B", 
             alpha=0.4,
             figsize=(10,7),
             #label="la la",
             s=df_test["C"]*100, 
             c="D", 
             cmap=plt.get_cmap("jet"), 
             colorbar=True,
)
plt.legend()

运行上面的代码会给出一个抱怨No handles with labels found to put in legend (不出所料)和一些不推荐使用的警告，但会显示一个图表。这些点的颜色很好，您甚至可能会看到空的图例框。

现在，取消对标签行的注释：

df_test.plot(kind="scatter", x="A", y="B", 
             alpha=0.4,
             figsize=(10,7),
             label="la la",
             s=df_test["C"]*100, 
             c="D", 
             cmap=plt.get_cmap("jet"), 
             colorbar=True,
)
plt.legend()

当我运行这个命令时，我得到一个TypeError: object of type 'NoneType' has no len()错误，如下所示：

---------------------------------------------------------------------------
TypeError                                 Traceback (most recent call last)
D:\anaconda\envs\tf-gpu\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)

D:\anaconda\envs\tf-gpu\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))

D:\anaconda\envs\tf-gpu\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':

D:\anaconda\envs\tf-gpu\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:

D:\anaconda\envs\tf-gpu\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()

D:\anaconda\envs\tf-gpu\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:

D:\anaconda\envs\tf-gpu\lib\site-packages\matplotlib\figure.py in draw(self, renderer)
   2732 
   2733             self.patch.draw(renderer)
-> 2734             mimage._draw_list_compositing_images(
   2735                 renderer, self, artists, self.suppressComposite)
   2736 

D:\anaconda\envs\tf-gpu\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

D:\anaconda\envs\tf-gpu\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:

D:\anaconda\envs\tf-gpu\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

D:\anaconda\envs\tf-gpu\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')

D:\anaconda\envs\tf-gpu\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

D:\anaconda\envs\tf-gpu\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:

D:\anaconda\envs\tf-gpu\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')

D:\anaconda\envs\tf-gpu\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.))

D:\anaconda\envs\tf-gpu\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.))

D:\anaconda\envs\tf-gpu\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.))

D:\anaconda\envs\tf-gpu\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.))

D:\anaconda\envs\tf-gpu\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.))

D:\anaconda\envs\tf-gpu\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:

D:\anaconda\envs\tf-gpu\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 

D:\anaconda\envs\tf-gpu\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:

D:\anaconda\envs\tf-gpu\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()

对于着色和label=，这似乎是与c=的交互。如果我注释掉颜色的东西(c=，cmap，colorbar)，绘图会呈现一个图例框，我们看到它也可以使用包含的颜色和注释掉的标签。我也尝试过重启内核，也有同样的结果。我还没有尝试用其他版本创建新的环境，因为我想看看这是不是只有我一个人，或者其他人可以复制的东西。

(顺便说一句，在Colab上，python 3.7.10，pandas 1.1.5，matplotlib 3.2.2上，代码看起来确实可以工作(有一个小的figsize问题)，所以可能是关于这些包的较新版本，或者我的设置...)

所以，请仁慈，但谁能指出我这里漏掉了什么愚蠢的东西吗？有什么建议吗？有没有人能复制？

Answer 1

可能是旧版本中的错误，因为它在matplotlib的最新版本上运行得很好。建议只更新matplotlib和pandas。不要在这上面逗留太久。