Hej，
我使用的是最新版本（1.2.0）的matplotlib，与macports一起分发。我遇到断言错误（我猜源于内部测试）运行此代码
#!/usr/bin/env python
import numpy as np
import matplotlib.pyplot as plt
X,Y = np.meshgrid(np.arange(0, 2*np.pi, .2), np.arange(0, 2*np.pi, .2))
U = np.cos(X)
V = np.sin(Y)
Q = plt.quiver(U, V)
plt.quiverkey(Q, 0.5, .9, 1., 'Label')
plt.gca().add_patch(plt.Circle((10, 10), 1))
plt.savefig('test.pdf')
我需要此代码的三个部分来重现错误：
- 箭袋图必须有一个使用箭袋键创建的密钥
- 必须在当前轴上添加额外的补丁
- 我必须将图形另存为PDF（我可以很好地显示它）
该错误不依赖于后端。我得到的回溯
读取Traceback (most recent call last):
File "./test_quiver.py", line 15, in <module>
plt.savefig('test.pdf')
File "/opt/local/Library/Frameworks/Python.framework/Versions/2.7/lib/python2.7/site-packages/matplotlib/pyplot.py", line 472, in savefig
return fig.savefig(*args, **kwargs)
File "/opt/local/Library/Frameworks/Python.framework/Versions/2.7/lib/python2.7/site-packages/matplotlib/figure.py", line 1363, in savefig
self.canvas.print_figure(*args, **kwargs)
File "/opt/local/Library/Frameworks/Python.framework/Versions/2.7/lib/python2.7/site-packages/matplotlib/backend_bases.py", line 2093, in print_figure
**kwargs)
File "/opt/local/Library/Frameworks/Python.framework/Versions/2.7/lib/python2.7/site-packages/matplotlib/backend_bases.py", line 1845, in print_pdf
return pdf.print_pdf(*args, **kwargs)
File "/opt/local/Library/Frameworks/Python.framework/Versions/2.7/lib/python2.7/site-packages/matplotlib/backends/backend_pdf.py", line 2301, in print_pdf
self.figure.draw(renderer)
File "/opt/local/Library/Frameworks/Python.framework/Versions/2.7/lib/python2.7/site-packages/matplotlib/artist.py", line 54, in draw_wrapper
draw(artist, renderer, *args, **kwargs)
File "/opt/local/Library/Frameworks/Python.framework/Versions/2.7/lib/python2.7/site-packages/matplotlib/figure.py", line 999, in draw
func(*args)
File "/opt/local/Library/Frameworks/Python.framework/Versions/2.7/lib/python2.7/site-packages/matplotlib/artist.py", line 54, in draw_wrapper
draw(artist, renderer, *args, **kwargs)
File "/opt/local/Library/Frameworks/Python.framework/Versions/2.7/lib/python2.7/site-packages/matplotlib/axes.py", line 2086, in draw
a.draw(renderer)
File "/opt/local/Library/Frameworks/Python.framework/Versions/2.7/lib/python2.7/site-packages/matplotlib/artist.py", line 54, in draw_wrapper
draw(artist, renderer, *args, **kwargs)
File "/opt/local/Library/Frameworks/Python.framework/Versions/2.7/lib/python2.7/site-packages/matplotlib/quiver.py", line 306, in draw
self.vector.draw(renderer)
File "/opt/local/Library/Frameworks/Python.framework/Versions/2.7/lib/python2.7/site-packages/matplotlib/artist.py", line 54, in draw_wrapper
draw(artist, renderer, *args, **kwargs)
File "/opt/local/Library/Frameworks/Python.framework/Versions/2.7/lib/python2.7/site-packages/matplotlib/collections.py", line 755, in draw
return Collection.draw(self, renderer)
File "/opt/local/Library/Frameworks/Python.framework/Versions/2.7/lib/python2.7/site-packages/matplotlib/artist.py", line 54, in draw_wrapper
draw(artist, renderer, *args, **kwargs)
File "/opt/local/Library/Frameworks/Python.framework/Versions/2.7/lib/python2.7/site-packages/matplotlib/collections.py", line 259, in draw
self._offset_position)
File "/opt/local/Library/Frameworks/Python.framework/Versions/2.7/lib/python2.7/site-packages/matplotlib/backends/backend_pdf.py", line 1548, in draw_path_collection
output(*self.gc.pop())
File "/opt/local/Library/Frameworks/Python.framework/Versions/2.7/lib/python2.7/site-packages/matplotlib/backends/backend_pdf.py", line 2093, in pop
assert self.parent is not None
AssertionError
以防万一：我使用的是Mac OS X 10.7.5，使用python 2.7.3和matplotlib 1.2.0。你也收到这个错误吗？它是 matplotlib 中的错误吗？它是否依赖于系统？有什么解决方法吗？
您可以另存为 eps 或 svg 并转换为 pdf。我发现生成小pdf文件的最佳方法是在matplotlib中另存为eps，然后使用epstopdf。
svg也可以正常工作，您可以使用Inkscape转换为pdf。svg 的副作用是文本被转换为路径（没有嵌入字体），这在某些情况下可能是可取的。
与 Ubuntu 13.04 （raring） 一起分发的 matplotlib （v 1.2.1） 也有这个错误。 我不知道在较新版本中是否仍然是一个问题。
另一种解决方法（似乎对我有用）是完全删除 .../matplotlib/backends/backend_pdf.py 中的 draw_path_collection 函数。