当DISPLAY未定义时，使用matplotlib生成PNG

Question

我正在尝试将networkx与Python一起使用。当我运行此程序时，它会收到此错误。有什么遗漏吗？

#!/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

---

我现在得到一个不同的错误：

#!/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

---

我现在得到一个不同的错误：

#!/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

Answer 1

主要问题是（在你的系统上）matplotlib默认选择x-using后端。我在我的一台服务器上遇到了同样的问题。我的解决方案是将以下代码添加到之前读取任何其他pylab / matplotlib / pyplot 导入的地方：

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

另一种方法是将其设置在.matplotlibrc

中

Answer 2

正如Reinout的回答一样。

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。就是这样。

Answer 3

干净的答案是花一点时间正确准备你的执行环境。

准备执行环境的第一项技巧是使用matplotlibrc文件，as wisely recommended by Chris Q.，设置

backend : Agg

在该文件中。您甚至可以控制 - 无需更改代码 - how and where matplotlib looks for and finds the matplotlibrc file。

准备执行环境的第二种技巧是使用MPLBACKEND environment variable（并告知用户使用它）：

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来使其工作。我采用这种方法，例如，在持续集成中进行测试，并在没有显示器的远程机器上运行。

在你的Python代码中将matplotlib后端硬编码为“Agg”就好像用一把大锤子将方形钉子钉入一个圆孔中，相反，你可能只是告诉matplotlib它需要是一个方孔。

Answer 4

通过Spark使用matplotlib时出错了。 matplotlib.use('Agg')对我不起作用。最后，以下代码适用于我。更多here

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

Answer 5

我将重复@Ivo Bosticky所说的可以忽略的内容。将这些行放在py文件的非常开头。

import matplotlib
matplotlib.use('Agg') 

或者会有错误

*/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,*

这将解决所有显示问题

Answer 6

登录服务器以执行代码时 请改用：

ssh -X username@servername

-X将删除无显示名称和$ DISPLAY环境变量 错误

：）

Answer 7

我发现这个代码段在X和no-X环境之间切换时效果很好。

.comp-insp-th .th-cell .flex{
  -ms-flex:1 0 30px !important;
}

Answer 8

你在哪个系统？看起来你有一个带X11的系统，但没有正确设置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

Answer 9

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

它对我有用。

Answer 10

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，root不被允许这样做，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

Answer 11

为确保您的代码可在Windows，Linux和OSX上以及在具有和不具有显示功能的系统之间移植，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

Answer 12

对于Google Cloud Machine学习引擎：

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)