Let's say something like this is being returned.

No module named '_ctypes'

I could reproduce this by running Python with the -m ctypes option.

~]# /usr/local/bin/python3.10.2/bin/python3.10 -m ctypes
Traceback (most recent call last):
  File "/usr/local/bin/python3.10.2/lib/python3.10/runpy.py", line 187, in _run_module_as_main
    mod_name, mod_spec, code = _get_module_details(mod_name, _Error)
  File "/usr/local/bin/python3.10.2/lib/python3.10/runpy.py", line 146, in _get_module_details
    return _get_module_details(pkg_main_name, error)
  File "/usr/local/bin/python3.10.2/lib/python3.10/runpy.py", line 110, in _get_module_details
    __import__(pkg_name)
  File "/usr/local/bin/python3.10.2/lib/python3.10/ctypes/__init__.py", line 8, in <module>
    from _ctypes import Union, Structure, Array
ModuleNotFoundError: No module named '_ctypes

I got this after installing Python from source and my system did not contain the libffi-dev or libffi-devel package.

]# yum list installed | grep libffi
libffi.x86_64                       3.0.13-19.el7            @rhel-7-server-rpms

I resolved this by first installing the libffi-devel package.

dnf install libffi-devel

And validated the libffi-devel package was installed.

~]# yum list installed | grep libffi
libffi.x86_64                       3.0.13-19.el7            @rhel-7-server-rpms
libffi-devel.x86_64                 3.0.13-19.el7            @rhel-7-server-rpms

Then I reinstalled Python from source and I no longer got the error.