Matplotlib:删除有关matplotlib.use()的警告

Question

在我使用的Python模块中matplotlib,我想确保它在我通过远程计算机运行脚本时也能正常工作ssh.所以我这样做:

import matplotlib
matplotlib.use('Agg')
from matplotlib.backends.backend_pdf import PdfPages
import matplotlib.mlab as mlab
import matplotlib.pyplot as plt
import numpy as np
import pylab
import scipy.stats
import scipy.stats.mstats

有用.太糟糕了,当我直接在机器上运行它(不是远程机器!)时,它给了我以下警告:

对matplotlib.use()的这个调用没有效果,因为已经选择了后端; 必须 在首次导入pylab,matplotlib.pyplot或matplotlib.backends 之前调用matplotlib.use().

如何删除此邮件？

Answer 1

虽然我无法测试这个Ipython告诉我"人们可以设置warn = False以禁止警告."

资源:

matplotlib.use?

Type:       function
String Form:<function use at 0x98da02c>
File:       /usr/lib/pymodules/python2.7/matplotlib/__init__.py
Definition: matplotlib.use(arg, warn=True)
Docstring:
Set the matplotlib backend to one of the known backends.

The argument is case-insensitive.  For the Cairo backend,
the argument can have an extension to indicate the type of
output.  Example:

    use('cairo.pdf')

will specify a default of pdf output generated by Cairo.

.. note::

    This function must be called *before* importing pyplot for
    the first time; or, if you are not using pyplot, it must be called
    before importing matplotlib.backends.  If warn is True, a warning
    is issued if you try and call this after pylab or pyplot have been
    loaded.  In certain black magic use cases, e.g.
    :func:`pyplot.switch_backends`, we are doing the reloading necessary to
    make the backend switch work (in some cases, e.g. pure image
    backends) so one can set warn=False to supporess the warnings.

To find out which backend is currently set, see
:func:`matplotlib.get_backend`.

在文档中找到拼写错误总是很有趣.

Answer 2

警告消息通常很重要，我建议不要忽略。我在寻找使用 sphinx 构建文档的解决方案时发现了您的问题。我收到了类似的消息，以及警告的一些附加上下文：

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.

The backend was originally set to 'Qt5Agg' by the following code:
File "setup.py", line 131, in <module>
'psql' : ['psycopg2>=2.7.1'],

然后我在https://github.com/conchoecia/pauvre/issues/18找到了解决方案。进口订单如下：

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

在修复之前，我只对模块进行了以下导入

from mymod.utils import plotutils
import mymod.plots as plots
import matplotlib.pyplot as plt

我认为这个问题的导入订单导致了警告消息。但是，我无法根据您提供的信息重现您的警告。如果能从该警告中看到更多的内容就太好了。

经过与其他开发人员的更多讨论后，很明显我导入的 pyplot 位于该文件中，而它属于我需要使用 plt 的模块中。

了解渲染非常重要，您可以在 https://matplotlib.org/faq/usage_faq.html#what-is-a-backend 和 https://matplotlib.org/api/matplotlib_configuration_api.html#matplotlib 获取更多信息。使用 请记住其他正在进行的代码可能会更改或默认后端名称。