不能使用 matplotlib.use('Agg')，图形总是显示在屏幕上 [英] Can't use matplotlib.use('Agg'), graphs always show on the screen

问题描述

我正在研究 matplotlib，不知道如何只保存图形而不将其打印在屏幕上.

I'm studying matplotlib and don't know how to just save the graph and not print it on the screen.

所以我在网上做了一些研究，很多答案都说解决方案是matplotlib.use('Agg').并且必须在导入 matplotlib.pyplot 或 pylab 之前.

So I've done some research on the Internet, many answers said the solution is matplotlib.use('Agg'). And it must be before importing matplotlib.pyplot or pylab.

然后当我将它添加到脚本的第一行时，它根本不起作用.

Then when I added it in the first line of my script, it doesn't work at all.

import matplotlib
matplotlib.use('Agg') 
import numpy as np
import pandas as pd
import matplotlib.pyplot as plt

E:Program FilesAnaconda3libsite-packagesmatplotlib\__init__.py:1401: UserWarning:  This call to matplotlib.use() has no effect
because the backend has already been chosen;
matplotlib.use() must be called *before* pylab, matplotlib.pyplot,
or matplotlib.backends is imported for the first time.

  warnings.warn(_use_error_msg)

我使用 Anaconda Spyder，所以我重新启动内核并再次运行我的脚本，我得到了同样的错误信息.

I use Anaconda Spyder, so I restarted kernel and ran my script again, I got same wrong information.

然后我再次重启内核，直接在控制台输入如下代码:

Then I restarted kernel again and directly typed the following code in the console:

In[1]: import matplotlib as mpl

In[2]: mpl.use('Agg')

E:Program FilesAnaconda3libsite-packagesmatplotlib\__init__.py:1401: UserWarning:  This call to matplotlib.use() has no effect
because the backend has already been chosen;
matplotlib.use() must be called *before* pylab, matplotlib.pyplot,
or matplotlib.backends is imported for the first time.

  warnings.warn(_use_error_msg)

另外，如果我在脚本末尾删除 'plt.show()' 或添加 'plt.ioff()'，图表将始终打印在屏幕上.

Also, if I delete 'plt.show()' at the end of script or add 'plt.ioff()', the graph will always print on the screen.

感谢大家的回答.现在我有两个解决方案:

Thanks for everyone's answer. Now I have two solutions:

1. 只需使用 plt.close() ，这不会改变后端并且不会显示图形.

1. just use plt.close() , this will not change the backend and the figure doesn't show up.

使用plt.switch_backend('Agg')，这会将后端切换为'agg'，屏幕上不会打印任何图形.

use plt.switch_backend('Agg'), this will switch the backend to 'agg' and no figure printed on the screen.

推荐答案

可以尝试切换后端.显然 Spyder 会先加载 matplotlib，而 use 没有任何效果.这可能会有所帮助:如何在matplotlib/Python中切换后端

You can try to switch the backend. Apparently Spyder loads matplotlib before you do, and use has no effect. This may be helpful: How to switch backends in matplotlib / Python

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