昨天晚上我的pyplot函数还能用，今天就不行了。在终端显示，matplotlib还能正常用，但pyplot用不了。

Python 3.7.2 (tags/v3.7.2:9a3ffc0492, Dec 23 2018, 22:20:52) [MSC v.1916 32 bit (Intel)] on win32
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>>> import matplotlib
>>> import matplotlib.pyplot as plt
Traceback (most recent call last):
File "<stdin>", line 1, in <module>
File "C:\Users\王江伟\AppData\Roaming\Python\Python37\site-packages\matplotlib\pyplot.py", line 40, in <module>
from matplotlib.figure import Figure, figaspect
File "C:\Users\王江伟\AppData\Roaming\Python\Python37\site-packages\matplotlib\figure.py", line 37, in <module>
from matplotlib.axes import Axes, SubplotBase, subplot_class_factory
File "C:\Users\王江伟\AppData\Roaming\Python\Python37\site-packages\matplotlib\axes\__init__.py", line 1, in <module>
from ._subplots import *
File "C:\Users\王江伟\AppData\Roaming\Python\Python37\site-packages\matplotlib\axes\_subplots.py", line 6, in <module>
from matplotlib.axes._axes import Axes
File "C:\Users\王江伟\AppData\Roaming\Python\Python37\site-packages\matplotlib\axes\_axes.py", line 36, in <module>
import matplotlib.tri as mtri
File "C:\Users\王江伟\AppData\Roaming\Python\Python37\site-packages\matplotlib\tri\__init__.py", line 5, in <module>
from .triangulation import *
File "C:\Users\王江伟\AppData\Roaming\Python\Python37\site-packages\matplotlib\tri\triangulation.py", line 4, in <module>
import matplotlib._qhull as _qhull
ModuleNotFoundError: No module named 'matplotlib._qhull'
>>>

请问这是怎么回事？该怎么解决呢？