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问题：未定义DISPLAY时，使用matplotlib生成PNG
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问题：未定义DISPLAY时，使用matplotlib生成PNG

我正在尝试将networkx与Python结合使用。当我运行该程序时，出现此错误。缺少什么吗？

#!/usr/bin/env python

import networkx as nx
import matplotlib
import matplotlib.pyplot
import matplotlib.pyplot as plt

G=nx.Graph()
G.add_node(1)
G.add_nodes_from([2,3,4,5,6,7,8,9,10])
#nx.draw_graphviz(G)
#nx_write_dot(G, 'node.png')
nx.draw(G)
plt.savefig("/var/www/node.png")


Traceback (most recent call last):
  File "graph.py", line 13, in <module>
    nx.draw(G)
  File "/usr/lib/pymodules/python2.5/networkx/drawing/nx_pylab.py", line 124, in draw
    cf=pylab.gcf()
  File "/usr/lib/pymodules/python2.5/matplotlib/pyplot.py", line 276, in gcf
    return figure()
  File "/usr/lib/pymodules/python2.5/matplotlib/pyplot.py", line 254, in figure
    **kwargs)
  File "/usr/lib/pymodules/python2.5/matplotlib/backends/backend_tkagg.py", line 90, in new_figure_manager
    window = Tk.Tk()
  File "/usr/lib/python2.5/lib-tk/Tkinter.py", line 1650, in __init__
    self.tk = _tkinter.create(screenName, baseName, className, interactive, wantobjects, useTk, sync, use)
_tkinter.TclError: no display name and no $DISPLAY environment variable

我现在收到另一个错误：

#!/usr/bin/env python

import networkx as nx
import matplotlib
import matplotlib.pyplot
import matplotlib.pyplot as plt

matplotlib.use('Agg')

G=nx.Graph()
G.add_node(1)
G.add_nodes_from([2,3,4,5,6,7,8,9,10])
#nx.draw_graphviz(G)
#nx_write_dot(G, 'node.png')
nx.draw(G)
plt.savefig("/var/www/node.png")
/usr/lib/pymodules/python2.5/matplotlib/__init__.py:835: UserWarning:  This call to matplotlib.use() has no effect
because the the backend has already been chosen;
matplotlib.use() must be called *before* pylab, matplotlib.pyplot,
or matplotlib.backends is imported for the first time.

  if warn: warnings.warn(_use_error_msg)
Traceback (most recent call last):
  File "graph.py", line 15, in <module>
    nx.draw(G)
  File "/usr/lib/python2.5/site-packages/networkx-1.2.dev-py2.5.egg/networkx/drawing/nx_pylab.py", line 124, in draw
    cf=pylab.gcf()
  File "/usr/lib/pymodules/python2.5/matplotlib/pyplot.py", line 276, in gcf
    return figure()
  File "/usr/lib/pymodules/python2.5/matplotlib/pyplot.py", line 254, in figure
    **kwargs)
  File "/usr/lib/pymodules/python2.5/matplotlib/backends/backend_tkagg.py", line 90, in new_figure_manager
    window = Tk.Tk()
  File "/usr/lib/python2.5/lib-tk/Tkinter.py", line 1650, in __init__
    self.tk = _tkinter.create(screenName, baseName, className, interactive, wantobjects, useTk, sync, use)
_tkinter.TclError: no display name and no $DISPLAY environment variable

我现在收到另一个错误：

#!/usr/bin/env python

import networkx as nx
import matplotlib
import matplotlib.pyplot
import matplotlib.pyplot as plt

matplotlib.use('Agg')

G=nx.Graph()
G.add_node(1)
G.add_nodes_from([2,3,4,5,6,7,8,9,10])
#nx.draw_graphviz(G)
#nx_write_dot(G, 'node.png')
nx.draw(G)
plt.savefig("/var/www/node.png")
/usr/lib/pymodules/python2.5/matplotlib/__init__.py:835: UserWarning:  This call to matplotlib.use() has no effect
because the the backend has already been chosen;
matplotlib.use() must be called *before* pylab, matplotlib.pyplot,
or matplotlib.backends is imported for the first time.

  if warn: warnings.warn(_use_error_msg)
Traceback (most recent call last):
  File "graph.py", line 15, in <module>
    nx.draw(G)
  File "/usr/lib/python2.5/site-packages/networkx-1.2.dev-py2.5.egg/networkx/drawing/nx_pylab.py", line 124, in draw
    cf=pylab.gcf()
  File "/usr/lib/pymodules/python2.5/matplotlib/pyplot.py", line 276, in gcf
    return figure()
  File "/usr/lib/pymodules/python2.5/matplotlib/pyplot.py", line 254, in figure
    **kwargs)
  File "/usr/lib/pymodules/python2.5/matplotlib/backends/backend_tkagg.py", line 90, in new_figure_manager
    window = Tk.Tk()
  File "/usr/lib/python2.5/lib-tk/Tkinter.py", line 1650, in __init__
    self.tk = _tkinter.create(screenName, baseName, className, interactive, wantobjects, useTk, sync, use)
_tkinter.TclError: no display name and no $DISPLAY environment variable
点击查看英文原文

I am trying to use networkx with Python. When I run this program it get this error. Is there anything missing?

#!/usr/bin/env python

import networkx as nx
import matplotlib
import matplotlib.pyplot
import matplotlib.pyplot as plt

G=nx.Graph()
G.add_node(1)
G.add_nodes_from([2,3,4,5,6,7,8,9,10])
#nx.draw_graphviz(G)
#nx_write_dot(G, 'node.png')
nx.draw(G)
plt.savefig("/var/www/node.png")


Traceback (most recent call last):
  File "graph.py", line 13, in <module>
    nx.draw(G)
  File "/usr/lib/pymodules/python2.5/networkx/drawing/nx_pylab.py", line 124, in draw
    cf=pylab.gcf()
  File "/usr/lib/pymodules/python2.5/matplotlib/pyplot.py", line 276, in gcf
    return figure()
  File "/usr/lib/pymodules/python2.5/matplotlib/pyplot.py", line 254, in figure
    **kwargs)
  File "/usr/lib/pymodules/python2.5/matplotlib/backends/backend_tkagg.py", line 90, in new_figure_manager
    window = Tk.Tk()
  File "/usr/lib/python2.5/lib-tk/Tkinter.py", line 1650, in __init__
    self.tk = _tkinter.create(screenName, baseName, className, interactive, wantobjects, useTk, sync, use)
_tkinter.TclError: no display name and no $DISPLAY environment variable

I get a different error now:

#!/usr/bin/env python

import networkx as nx
import matplotlib
import matplotlib.pyplot
import matplotlib.pyplot as plt

matplotlib.use('Agg')

G=nx.Graph()
G.add_node(1)
G.add_nodes_from([2,3,4,5,6,7,8,9,10])
#nx.draw_graphviz(G)
#nx_write_dot(G, 'node.png')
nx.draw(G)
plt.savefig("/var/www/node.png")

/usr/lib/pymodules/python2.5/matplotlib/__init__.py:835: UserWarning:  This call to matplotlib.use() has no effect
because the the backend has already been chosen;
matplotlib.use() must be called *before* pylab, matplotlib.pyplot,
or matplotlib.backends is imported for the first time.

  if warn: warnings.warn(_use_error_msg)
Traceback (most recent call last):
  File "graph.py", line 15, in <module>
    nx.draw(G)
  File "/usr/lib/python2.5/site-packages/networkx-1.2.dev-py2.5.egg/networkx/drawing/nx_pylab.py", line 124, in draw
    cf=pylab.gcf()
  File "/usr/lib/pymodules/python2.5/matplotlib/pyplot.py", line 276, in gcf
    return figure()
  File "/usr/lib/pymodules/python2.5/matplotlib/pyplot.py", line 254, in figure
    **kwargs)
  File "/usr/lib/pymodules/python2.5/matplotlib/backends/backend_tkagg.py", line 90, in new_figure_manager
    window = Tk.Tk()
  File "/usr/lib/python2.5/lib-tk/Tkinter.py", line 1650, in __init__
    self.tk = _tkinter.create(screenName, baseName, className, interactive, wantobjects, useTk, sync, use)
_tkinter.TclError: no display name and no $DISPLAY environment variable

I get a different error now:

#!/usr/bin/env python

import networkx as nx
import matplotlib
import matplotlib.pyplot
import matplotlib.pyplot as plt

matplotlib.use('Agg')

G=nx.Graph()
G.add_node(1)
G.add_nodes_from([2,3,4,5,6,7,8,9,10])
#nx.draw_graphviz(G)
#nx_write_dot(G, 'node.png')
nx.draw(G)
plt.savefig("/var/www/node.png")

/usr/lib/pymodules/python2.5/matplotlib/__init__.py:835: UserWarning:  This call to matplotlib.use() has no effect
because the the backend has already been chosen;
matplotlib.use() must be called *before* pylab, matplotlib.pyplot,
or matplotlib.backends is imported for the first time.

  if warn: warnings.warn(_use_error_msg)
Traceback (most recent call last):
  File "graph.py", line 15, in <module>
    nx.draw(G)
  File "/usr/lib/python2.5/site-packages/networkx-1.2.dev-py2.5.egg/networkx/drawing/nx_pylab.py", line 124, in draw
    cf=pylab.gcf()
  File "/usr/lib/pymodules/python2.5/matplotlib/pyplot.py", line 276, in gcf
    return figure()
  File "/usr/lib/pymodules/python2.5/matplotlib/pyplot.py", line 254, in figure
    **kwargs)
  File "/usr/lib/pymodules/python2.5/matplotlib/backends/backend_tkagg.py", line 90, in new_figure_manager
    window = Tk.Tk()
  File "/usr/lib/python2.5/lib-tk/Tkinter.py", line 1650, in __init__
    self.tk = _tkinter.create(screenName, baseName, className, interactive, wantobjects, useTk, sync, use)
_tkinter.TclError: no display name and no $DISPLAY environment variable

回答 0

主要问题是（在您的系统上）matplotlib默认情况下选择使用x的后端。我在其中一台服务器上遇到了同样的问题。对我来说，解决方案是在任何其他pylab / matplotlib / pyplot导入之前先读取的位置添加以下代码：

import matplotlib
# Force matplotlib to not use any Xwindows backend.
matplotlib.use('Agg')

另一种方法是在您的.matplotlibrc中进行设置

点击查看英文原文

The main problem is that (on your system) matplotlib chooses an x-using backend by default. I just had the same problem on one of my servers. The solution for me was to add the following code in a place that gets read before any other pylab/matplotlib/pyplot import:

import matplotlib
# Force matplotlib to not use any Xwindows backend.
matplotlib.use('Agg')

The alternative is to set it in your .matplotlibrc

回答 1

只是对Reinout的回答的补充。

解决此类问题的永久方法是编辑.matplotlibrc文件。通过找到它

>>> import matplotlib
>>> matplotlib.matplotlib_fname()
# This is the file location in Ubuntu
'/etc/matplotlibrc'

然后将该文件中的后端修改为backend : Agg。这就对了。

点击查看英文原文

Just as a complement of Reinout’s answer.

The permanent way to solve this kind of problem is to edit .matplotlibrc file. Find it via

>>> import matplotlib
>>> matplotlib.matplotlib_fname()
# This is the file location in Ubuntu
'/etc/matplotlibrc'

Then modify the backend in that file to backend : Agg. That is it.

回答 2

明确的答案是花一些时间正确准备执行环境。

你必须准备执行环境第一种方法是使用一个matplotlibrc文件，明智地由克里斯Q.建议，设置

backend : Agg

在那个文件中。您甚至可以控制matplotlib查找和查找matplotlibrc文件的方式和位置，而无需更改代码。

准备执行环境的第二种技术是使用MPLBACKEND环境变量（并通知您的用户使用它）：

export MPLBACKEND="agg"
python <program_using_matplotlib.py>

这很方便，因为您甚至不必在磁盘上提供另一个文件即可完成此工作。我采用了这种方法，例如进行持续集成测试，并在没有显示器的远程计算机上运行。

在您的Python代码中将matplotlib后端硬编码为“ Agg”，就像用大铁锤将方钉砸成一个圆孔，相反，您本可以告诉matplotlib它必须是方孔。

点击查看英文原文

The clean answer is to take a little bit of time correctly prepare your execution environment.

The first technique you have to prepare your execution environment is to use a matplotlibrc file, as wisely recommended by Chris Q., setting

backend : Agg

in that file. You can even control — with no code changes — how and where matplotlib looks for and finds the matplotlibrc file.

The second technique you have to prepare your execution environment is to use the MPLBACKEND environment variable (and inform your users to make use of it):

export MPLBACKEND="agg"
python <program_using_matplotlib.py>

This is handy because you don’t even have to provide another file on disk to make this work. I have employed this approach with, for example, testing in continuous integration, and running on remote machines that do not have displays.

Hard-coding your matplotlib backend to “Agg” in your Python code is like bashing a square peg into a round hole with a big hammer, when, instead, you could have just told matplotlib it needs to be a square hole.

回答 3

通过Spark使用matplotlib时出现错误。matplotlib.use('Agg')对我不起作用。最后，以下代码对我有用。这里更多

import matplotlib.pyplot as plt.
plt.switch_backend('agg')
点击查看英文原文

I got the error while using matplotlib through Spark. matplotlib.use('Agg') doesn’t work for me. In the end, the following code works for me. More here

import matplotlib.pyplot as plt.
plt.switch_backend('agg')

回答 4

我将重复@Ivo Bosticky所说的话，但可以忽略。将这些行放在py文件的非常开头。

import matplotlib
matplotlib.use('Agg')

否则会出错 

* / usr / lib / pymodules / python2.7 / matplotlib / __ init__.py:923：UserWarning：此对matplotlib.use（）的调用无效
因为已经选择了后端；
必须在pylab，matplotlib.pyplot，*之前调用matplotlib.use（）

这将解决所有显示问题

点击查看英文原文

I will just repeat what @Ivo Bosticky said which can be overlooked. Put these lines at the VERY start of the py file.

import matplotlib
matplotlib.use('Agg')

Or one would get error 

*/usr/lib/pymodules/python2.7/matplotlib/__init__.py:923: UserWarning:  This call to   matplotlib.use() has no effect
because the the backend has already been chosen;
matplotlib.use() must be called *before* pylab, matplotlib.pyplot,*

This will resolve all Display issue

回答 5

我发现此片段在X和非X环境之间切换时效果很好。

import os
import matplotlib as mpl
if os.environ.get('DISPLAY','') == '':
    print('no display found. Using non-interactive Agg backend')
    mpl.use('Agg')
import matplotlib.pyplot as plt
点击查看英文原文

I found this snippet to work well when switching between X and no-X environments.

import os
import matplotlib as mpl
if os.environ.get('DISPLAY','') == '':
    print('no display found. Using non-interactive Agg backend')
    mpl.use('Agg')
import matplotlib.pyplot as plt

回答 6

登录服务器以执行代码时，请改用以下命令：

ssh -X username@servername

在-X将摆脱没有显示名称并且没有$ DISPLAY环境变量错误

:)

点击查看英文原文

When signing into the server to execute the code use this instead:

ssh -X username@servername

the -X will get rid of the no display name and no $DISPLAY environment variable error

:)

回答 7

您在什么系统上？看起来您的系统具有X11，但未正确设置DISPLAY环境变量。尝试执行以下命令，然后重新运行程序：

export DISPLAY=localhost:0
点击查看英文原文

What system are you on? It looks like you have a system with X11, but the DISPLAY environment variable was not properly set. Try executing the following command and then rerunning your program:

export DISPLAY=localhost:0

回答 8

import matplotlib
matplotlib.use('Agg')
import matplotlib.pyplot as plt

这个对我有用。

点击查看英文原文 
import matplotlib
matplotlib.use('Agg')
import matplotlib.pyplot as plt

It works for me.

回答 9

要检查的另一件事是您当前的用户是否有权连接到X显示器。在我的情况下，不允许root执行此操作，并且matplotlib抱怨同样的错误。

user@debian:~$ xauth list         
debian/unix:10  MIT-MAGIC-COOKIE-1  ae921efd0026c6fc9d62a8963acdcca0
root@debian:~# xauth add debian/unix:10  MIT-MAGIC-COOKIE-1 ae921efd0026c6fc9d62a8963acdcca0
root@debian:~# xterm

来源：http : //www.debian-administration.org/articles/494 https://debian-administration.org/article/494/Getting_X11_forwarding_through_ssh_working_after_running_su

点击查看英文原文

One other thing to check is whether your current user is authorised to connect to the X display. In my case, root was not allowed to do that and matplotlib was complaining with the same error.

user@debian:~$ xauth list         
debian/unix:10  MIT-MAGIC-COOKIE-1  ae921efd0026c6fc9d62a8963acdcca0
root@debian:~# xauth add debian/unix:10  MIT-MAGIC-COOKIE-1 ae921efd0026c6fc9d62a8963acdcca0
root@debian:~# xterm

source: http://www.debian-administration.org/articles/494 https://debian-administration.org/article/494/Getting_X11_forwarding_through_ssh_working_after_running_su

回答 10

为了确保您的代码可在Windows，Linux和OSX上移植，以及对于带有和不带有显示器的系统，我建议使用以下代码段：

import matplotlib
import os
# must be before importing matplotlib.pyplot or pylab!
if os.name == 'posix' and "DISPLAY" not in os.environ:
    matplotlib.use('Agg')

# now import other things from matplotlib
import matplotlib.pyplot as plt

信用：https : //stackoverflow.com/a/45756291/207661

点击查看英文原文

To make sure your code is portable across Windows, Linux and OSX and for systems with and without displays, I would suggest following snippet:

import matplotlib
import os
# must be before importing matplotlib.pyplot or pylab!
if os.name == 'posix' and "DISPLAY" not in os.environ:
    matplotlib.use('Agg')

# now import other things from matplotlib
import matplotlib.pyplot as plt

Credit: https://stackoverflow.com/a/45756291/207661

回答 11

对于Google Cloud Machine Learning Engine：

import matplotlib as mpl
mpl.use('Agg')
from matplotlib.backends.backend_pdf import PdfPages

然后打印到文件：

#PDF build and save
    def multi_page(filename, figs=None, dpi=200):
        pp = PdfPages(filename)
        if figs is None:
            figs = [mpl.pyplot.figure(n) for n in mpl.pyplot.get_fignums()]
        for fig in figs:
            fig.savefig(pp, format='pdf', bbox_inches='tight', fig_size=(10, 8))
        pp.close()

并创建PDF：

multi_page(report_name)
点击查看英文原文

For Google Cloud Machine Learning Engine:

import matplotlib as mpl
mpl.use('Agg')
from matplotlib.backends.backend_pdf import PdfPages

And then to print to file:

#PDF build and save
    def multi_page(filename, figs=None, dpi=200):
        pp = PdfPages(filename)
        if figs is None:
            figs = [mpl.pyplot.figure(n) for n in mpl.pyplot.get_fignums()]
        for fig in figs:
            fig.savefig(pp, format='pdf', bbox_inches='tight', fig_size=(10, 8))
        pp.close()

and to create the PDF:

multi_page(report_name)
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