virtualenvwrapperModuleNotFoundError: No module named '_ctypes'

CentOS 7.0
Python 3.8.0

报错

ERROR: Command errored out with exit status 1:
     command: /root/.pyenv/versions/3.8.6/bin/python3.8 -c 'import sys, setuptools, tokenize; sys.argv[0] = '"'"'/tmp/pip-install-198v7rsw/virtualenvwrapper/setup.py'"'"'; __file__='"'"'/tmp/pip-install-198v7rsw/virtualenvwrapper/setup.py'"'"';f=getattr(tokenize, '"'"'open'"'"', open)(__file__);code=f.read().replace('"'"'\r\n'"'"', '"'"'\n'"'"');f.close();exec(compile(code, __file__, '"'"'exec'"'"'))' egg_info --egg-base /tmp/pip-pip-egg-info-sxzcb4vn
         cwd: /tmp/pip-install-198v7rsw/virtualenvwrapper/
    Complete output (11 lines):
    Traceback (most recent call last):
      File "", line 1, in 
      File "/root/.pyenv/versions/3.8.6/lib/python3.8/site-packages/setuptools/__init__.py", line 23, in 
        from setuptools.dist import Distribution
      File "/root/.pyenv/versions/3.8.6/lib/python3.8/site-packages/setuptools/dist.py", line 34, in 
        from setuptools import windows_support
      File "/root/.pyenv/versions/3.8.6/lib/python3.8/site-packages/setuptools/windows_support.py", line 2, in 
        import ctypes
      File "/root/.pyenv/versions/3.8.6/lib/python3.8/ctypes/__init__.py", line 7, in 
        from _ctypes import Union, Structure, Array
    ModuleNotFoundError: No module named '_ctypes'
    ----------------------------------------

解决

yum install libffi-devel -y
ldconfig

原理

Python3中有个内置模块叫ctypes，它是Python3的外部函数库模块，它提供兼容C语言的数据类型，并通过它调用Linux系统下的共享库(Shared library)，此模块需要使用CentOS7系统中外部函数库(Foreign function library)的开发链接库(头文件和链接库)。由于在CentOS7系统中没有安装外部函数库(libffi)的开发链接库软件包，所以在安装pip的时候就报了"ModuleNotFoundError: No module named '_ctypes'"的错误

参考

https://stackoverflow.com/questions/27022373/python3-importerror-no-module-named-ctypes-when-using-value-from-module-mul