创建RSA程序时出现ModuleNotFoundError

Question

（Python 3.7） 当我尝试导入Crypto.PublicKey时出现ModuleNotFoundError：

import crypto
from crypto.PublicKey import RSA

Traceback (most recent call last):
  File "<pyshell#10>", line 1, in <module>
    from crypto.PublicKey import RSA
  File "/Library/Frameworks/Python.framework/Versions/3.7/lib/python3.7/site-packages/crypto/PublicKey/RSA.py", line 73, in <module>
    from Crypto.Util.py3compat import *
ModuleNotFoundError: No module named 'Crypto'

否则我必须将Crypto导入为crypto（小写）

Traceback (most recent call last):
  File "<pyshell#4>", line 1, in <module>
    import Crypto
ModuleNotFoundError: No module named 'Crypto'

那么，如何正确导入Crypto的PublicKey中的RSA函数？