使用jupyter notebook时， 一直加载不出来
解决办法：在show函数里设置block参数为True
plt.show(block=True)
设置后图像就可以正常加载出来了
matplotlib文档对show函数的解释翻译：
matplotlib.pyplot.show( *args , **kw )
显示一个图形。在 ipython 及其 pylab 模式下运行时，显示所有图形并返回 ipython 提示符。
在非交互模式下，显示所有图形并阻塞，直到图形关闭；在交互模式下，除非在从非交互模式更改为交互模式之前创建图形（不推荐），否则它不起作用。在这种情况下，它会显示数字但不会阻塞。
单个实验性关键字参数block可以设置为 True 或 False 以覆盖上述阻止行为
原文档：
matplotlib.pyplot.show(*args, **kw)
Display a figure. When running in ipython with its pylab mode, display all figures and return to the ipython prompt.
In non-interactive mode, display all figures and block until the figures have been closed; in interactive mode it has no effect unless figures were created prior to a change from non-interactive to interactive mode (not recommended). In that case it displays the figures but does not block.
A single experimental keyword argument, block, may be set to True or False to override the blocking behavior described above.
感兴趣的可以自己去看看文档
pyplot — Matplotlib 2.0.2 documentationhttps://matplotlib.org/2.0.2/api/pyplot_api.html
