python matplotlib.pyplot.gca() 函数的作用

当前的图表和子图可以使用plt.gcf()和plt.gca()获得，分别表示Get Current Figure和Get Current Axes。在pyplot模块中，许多函数都是对当前的Figure或Axes对象进行处理，比如说：plt.plot()实际上会通过plt.gca()获得当前的Axes对象ax，然后再调用ax.plot()方法实现真正的绘图。

引用
https://blog.csdn.net/weixin_34150224/article/details/85932238

Signature: plt.gca(**kwargs)
Docstring:
Get the current :class:`~matplotlib.axes.Axes` instance on the
current figure matching the given keyword args, or create one.

Examples
--------
To get the current polar axes on the current figure::

    plt.gca(projection='polar')

If the current axes doesn't exist, or isn't a polar one, the appropriate
axes will be created and then returned.