python tclerror_python – _tkinter.TclError：没有显示名称和没...

我在服务器中运行一个简单的python脚本：

import matplotlib.pyplot as plt

import numpy as np

x = np.random.randn(60)

y = np.random.randn(60)

plt.scatter(x, y, s=20)

out_png = 'path/to/store/out_file.png'

plt.savefig(out_png, dpi=150)

我尝试在这个安装了matplotlib 1.5.1的服务器中使用命令python example.py,但失败并出现错误：

Traceback (most recent call last):

File "example.py", line 7, in

plt.scatter(x, y, s=20)

File "/home/USER/.virtualenvs/nnet/lib/python2.7/site-packages/matplotlib/pyplot.py", line 3241, in scatter

ax = gca()

File "/home/USER/.virtualenvs/nnet/lib/python2.7/site-packages/matplotlib/pyplot.py", line 928, in gca

return gcf().gca(**kwargs)

File "/home/USER/.virtualenvs/nnet/lib/python2.7/site-packages/matplotlib/pyplot.py", line 578, in gcf

return figure()

File "/home/USER/.virtualenvs/nnet/lib/python2.7/site-packages/matplotlib/pyplot.py", line 527, in figure

**kwargs)

File "/home/USER/.virtualenvs/nnet/lib/python2.7/site-packages/matplotlib/backends/backend_tkagg.py", line 84, in new_figure_manager

return new_figure_manager_given_figure(num, figure)

File "/home/USER/.virtualenvs/nnet/lib/python2.7/site-packages/matplotlib/backends/backend_tkagg.py", line 92, in new_figure_manager_given_figure

window = Tk.Tk()

File "/usr/local/lib/python2.7/lib-tk/Tkinter.py", line 1810, in __init__

self.tk = _tkinter.create(screenName, baseName, className, interactive, wantobjects, useTk, sync, use)

_tkinter.TclError: no display name and no $DISPLAY environment variable

这里发生了什么？