有一个类matplotlib.axes.AxesSubplot，但是模块matplotlib.axes没有属性AxesSubplot

Question

编码

import matplotlib.pyplot as plt
fig = plt.figure()
ax = fig.add_subplot(111)
print type(ax)

给出输出

<class 'matplotlib.axes.AxesSubplot'>

然后是代码

import matplotlib.axes
matplotlib.axes.AxesSubplot

引发异常

AttributeError: 'module' object has no attribute 'AxesSubplot'

总而言之，有一个类matplotlib.axes.AxesSubplot，但是模块matplotlib.axes没有attribute
AxesSubplot。到底是怎么回事？

我正在使用Matplotlib 1.1.0和Python 2.7.3。

Answer 1

嘿。这是因为有 是 无AxesSubplot类..直到有需要，当一个人从建SubplotBase。这是通过以下方法实现的axes.py：

def subplot_class_factory(axes_class=None):
    # This makes a new class that inherits from SubplotBase and the
    # given axes_class (which is assumed to be a subclass of Axes).
    # This is perhaps a little bit roundabout to make a new class on
    # the fly like this, but it means that a new Subplot class does
    # not have to be created for every type of Axes.
    if axes_class is None:
        axes_class = Axes

    new_class = _subplot_classes.get(axes_class)
    if new_class is None:
        new_class = new.classobj("%sSubplot" % (axes_class.__name__),
                                 (SubplotBase, axes_class),
                                 {'_axes_class': axes_class})
        _subplot_classes[axes_class] = new_class

    return new_class

因此它是即时生成的，但是它是的子类SubplotBase：

>>> import matplotlib.pyplot as plt
>>> fig = plt.figure()
>>> ax = fig.add_subplot(111)
>>> print type(ax)
<class 'matplotlib.axes.AxesSubplot'>
>>> b = type(ax)
>>> import matplotlib.axes
>>> issubclass(b, matplotlib.axes.SubplotBase)
True