我正在尝试在 Ubuntu 14.04 上的 Python 3 中使用 pylab (即$ ipython3 --pylab)。无论我使用 Tkinter 还是 Qt4 后端，我都会遇到相同的错误。
AttributeError: 'FontManager' object has no attribute 'ttf_lookup_cache'
但是，同样的基本绘图例程（plt.plot([1,2,3,4])）在 Python 2 pylab 中有效。
据我所知，我已经安装了必要的依赖项（注意，对于 Python 2 和 Python 3 都是如此）：
sudo apt-get install python-numpy python-scipy python-matplotlib
sudo apt-get install python3-numpy python3-scipy python3-matplotlib
sudo apt-get install python-tk python3-tk
sudo apt-get install libqt4gui libqt4core python-qt4 python3-qt4
完整回溯请见下文。这是 Tkinter：
$ ipython3 --matplotlib tk
Python 3.4.0 (default, Apr 11 2014, 13:05:11)
Type "copyright", "credits" or "license" for more information.
IPython 1.2.1 -- An enhanced Interactive Python.
? -> Introduction and overview of IPython's features.
%quickref -> Quick reference.
help -> Python's own help system.
object? -> Details about 'object', use 'object??' for extra details.
In [1]: import matplotlib.pyplot as plt
In [2]: plt.plot([1,2,3,4])
Out[2]: [<matplotlib.lines.Line2D at 0x7f1496dc9c50>]
In [3]: Exception in Tkinter callback
Traceback (most recent call last):
File "/usr/lib/python3.4/tkinter/__init__.py", line 1490, in __call__
return self.func(*args)
File "/usr/lib/python3.4/tkinter/__init__.py", line 535, in callit
func(*args)
File "/usr/lib/python3/dist-packages/matplotlib/backends/backend_tkagg.py", line 363, in idle_draw
self.draw()
File "/usr/lib/python3/dist-packages/matplotlib/backends/backend_tkagg.py", line 348, in draw
FigureCanvasAgg.draw(self)
File "/usr/lib/python3/dist-packages/matplotlib/backends/backend_agg.py", line 451, in draw
self.figure.draw(self.renderer)
File "/usr/lib/python3/dist-packages/matplotlib/artist.py", line 56, in draw_wrapper
draw(artist, renderer, *args, **kwargs)
File "/usr/lib/python3/dist-packages/matplotlib/figure.py", line 1035, in draw
func(*args)
File "/usr/lib/python3/dist-packages/matplotlib/artist.py", line 56, in draw_wrapper
draw(artist, renderer, *args, **kwargs)
File "/usr/lib/python3/dist-packages/matplotlib/axes.py", line 2088, in draw
a.draw(renderer)
File "/usr/lib/python3/dist-packages/matplotlib/artist.py", line 56, in draw_wrapper
draw(artist, renderer, *args, **kwargs)
File "/usr/lib/python3/dist-packages/matplotlib/axis.py", line 1094, in draw
renderer)
File "/usr/lib/python3/dist-packages/matplotlib/axis.py", line 1043, in _get_tick_bboxes
extent = tick.label1.get_window_extent(renderer)
File "/usr/lib/python3/dist-packages/matplotlib/text.py", line 755, in get_window_extent
bbox, info, descent = self._get_layout(self._renderer)
File "/usr/lib/python3/dist-packages/matplotlib/text.py", line 321, in _get_layout
ismath=False)
File "/usr/lib/python3/dist-packages/matplotlib/backends/backend_agg.py", line 214, in get_text_width_height_descent
font = self._get_agg_font(prop)
File "/usr/lib/python3/dist-packages/matplotlib/backends/backend_agg.py", line 258, in _get_agg_font
fname = findfont(prop)
File "/usr/lib/python3/dist-packages/matplotlib/font_manager.py", line 1362, in findfont
font = fontManager.findfont(prop, **kw)
File "/usr/lib/python3/dist-packages/matplotlib/font_manager.py", line 1202, in findfont
font_cache = self.ttf_lookup_cache
AttributeError: 'FontManager' object has no attribute 'ttf_lookup_cache'
以下是 Qt/Qt4 的情况：
$ ipython3 --matplotlib qt
WARNING: Attempting to work in a virtualenv. If you encounter problems, please install IPython inside the virtualenv.
Python 3.4.0 (default, Apr 11 2014, 13:05:11)
Type "copyright", "credits" or "license" for more information.
IPython 1.2.1 -- An enhanced Interactive Python.
? -> Introduction and overview of IPython's features.
%quickref -> Quick reference.
help -> Python's own help system.
object? -> Details about 'object', use 'object??' for extra details.
In [1]: import matplotlib.pyplot as plt
In [2]: plt.plot([1,2,3,4])
Out[2]: [<matplotlib.lines.Line2D at 0x7f0f840947f0>]
In [3]: Traceback (most recent call last):
File "/usr/lib/python3/dist-packages/matplotlib/backends/backend_qt4.py", line 374, in idle_draw
self.draw()
File "/usr/lib/python3/dist-packages/matplotlib/backends/backend_qt4agg.py", line 154, in draw
FigureCanvasAgg.draw(self)
File "/usr/lib/python3/dist-packages/matplotlib/backends/backend_agg.py", line 451, in draw
self.figure.draw(self.renderer)
File "/usr/lib/python3/dist-packages/matplotlib/artist.py", line 56, in draw_wrapper
draw(artist, renderer, *args, **kwargs)
File "/usr/lib/python3/dist-packages/matplotlib/figure.py", line 1035, in draw
func(*args)
File "/usr/lib/python3/dist-packages/matplotlib/artist.py", line 56, in draw_wrapper
draw(artist, renderer, *args, **kwargs)
File "/usr/lib/python3/dist-packages/matplotlib/axes.py", line 2088, in draw
a.draw(renderer)
File "/usr/lib/python3/dist-packages/matplotlib/artist.py", line 56, in draw_wrapper
draw(artist, renderer, *args, **kwargs)
File "/usr/lib/python3/dist-packages/matplotlib/axis.py", line 1094, in draw
renderer)
File "/usr/lib/python3/dist-packages/matplotlib/axis.py", line 1043, in _get_tick_bboxes
extent = tick.label1.get_window_extent(renderer)
File "/usr/lib/python3/dist-packages/matplotlib/text.py", line 755, in get_window_extent
bbox, info, descent = self._get_layout(self._renderer)
File "/usr/lib/python3/dist-packages/matplotlib/text.py", line 321, in _get_layout
ismath=False)
File "/usr/lib/python3/dist-packages/matplotlib/backends/backend_agg.py", line 214, in get_text_width_height_descent
font = self._get_agg_font(prop)
File "/usr/lib/python3/dist-packages/matplotlib/backends/backend_agg.py", line 258, in _get_agg_font
fname = findfont(prop)
File "/usr/lib/python3/dist-packages/matplotlib/font_manager.py", line 1362, in findfont
font = fontManager.findfont(prop, **kw)
File "/usr/lib/python3/dist-packages/matplotlib/font_manager.py", line 1202, in findfont
font_cache = self.ttf_lookup_cache
AttributeError: 'FontManager' object has no attribute 'ttf_lookup_cache'
If you suspect this is an IPython bug, please report it at:
https://github.com/ipython/ipython/issues
or send an email to the mailing list at [email protected]
You can print a more detailed traceback right now with "%tb", or use "%debug"
to interactively debug it.
Extra-detailed tracebacks for bug-reporting purposes can be enabled via:
%config Application.verbose_crash=True
在这两种情况下，都会出现绘图窗口。在 Tkinter 的情况下，绘图是空白的（空的），但在 Qt4 中，我确实看到了正确的结果——但错误仍然触发。同样，这在 Python 2.7 中的任何后端都可以正常工作。我错过了什么？
答案1
我可以通过删除 matplotlib 字体缓存（Python 3 和 Python 2 字体缓存）来解决这个问题，例如，
rm /home/arthur/.cache/matplotlib/fontList*.cache
我现在可以使用任何其他以下环境初始化而不会出现错误：
ipython3 --pylab
ipython3 --matplotlib tk
ipython3 --matplotlib qt4