我正在尝试绘制图表（inline) of nltk代替jupyter-notebook。但出现错误：

TclError: no display name and no $DISPLAY environment variable

我尝试过设置$DISPLAY到不同的值：

$env DISPLAY=0.0
# or
$env DISPLAY=inline
# or
$env DISPLAY=

但出现错误（或类似错误）：

TclError: couldn't connect to display "0.0"

这是我的代码https://github.com/hyzhak/nltk-experiments/blob/master/main.ipynb https://github.com/hyzhak/nltk-experiments/blob/master/main.ipynb最后一个单元格。

环境：官方anaconda3 docker --continuumio/anaconda3:4.4.0 https://github.com/ContinuumIO/docker-images https://github.com/ContinuumIO/docker-images. With nltk==3.2.3 inside.

Python 3.6.1 |Anaconda 4.4.0 (64-bit)| (default, May 11 2017, 13:09:58) 
Type "copyright", "credits" or "license" for more information.

IPython 5.3.0 -- An enhanced Interactive Python.

我该如何解决这个错误以及inline nltk内的图形jupyter notebook?

Update 1

http://www.nltk.org/_modules/nltk/draw/tree.html#draw_trees http://www.nltk.org/_modules/nltk/draw/tree.html#draw_trees根据 nltk 树绘制的来源，它使用tkinter.

Update 2

我在官方 nltk github 存储库中问了同样的问题https://github.com/nltk/nltk/issues/1765 https://github.com/nltk/nltk/issues/1765

Update 3

我认为错误的原因可能是无头主机（docker）。我已经安装了xvfb但似乎已经足够注意了。

RUN apt-get install -y xvfb

Solution

我以为xvfb默认情况下启动，但应该显式运行。因此，在启动它后，我可以制作 nltk 树形图的屏幕截图。

import os
import nltk
from IPython.display import Image

chunkGram = r"""Chunk: {<RB.?>*<VB.?>*<NNP>+<NN>?}"""
chunkParser = nltk.RegexpParser(chunkGram)

tagged = [('Tonight', 'NN'), ('we', 'PRP'), ('are', 'VBP'), ('comforted', 'VBN'), ('by', 'IN'), ('the', 'DT'), ('hope', 'NN'), ('of', 'IN'), ('a', 'DT'), ('glad', 'JJ'), ('reunion', 'NN'), ('with', 'IN'), ('the', 'DT'), ('husband', 'NN'), ('who', 'WP'), ('was', 'VBD'), ('taken', 'VBN'), ('so', 'RB'), ('long', 'RB'), ('ago', 'RB'), (',', ','), ('and', 'CC'), ('we', 'PRP'), ('are', 'VBP'), ('grateful', 'JJ'), ('for', 'IN'), ('the', 'DT'), ('good', 'JJ'), ('life', 'NN'), ('of', 'IN'), ('Coretta', 'NNP'), ('Scott', 'NNP'), ('King', 'NNP'), ('.', '.')]
chunked = chunkParser.parse(tagged)
nltk.draw.tree.TreeView(chunked)._cframe.print_to_file('output.ps')
os.system('convert output.ps output.png')

Image(filename='output.png') 

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