1.查看yum文件

cat /usr/bin/yum
# 或者
cat /bin/yum

但是我没搞懂 这两个目录下的文件有啥区别，cat看是一样的

2.结果显示

centos7.9的

#!/usr/bin/python
import sys
try:
    import yum
except ImportError:
    print >> sys.stderr, """\
There was a problem importing one of the Python modules
required to run yum. The error leading to this problem was:

   %s

Please install a package which provides this module, or
verify that the module is installed correctly.

It's possible that the above module doesn't match the
current version of Python, which is:
%s

If you cannot solve this problem yourself, please go to
the yum faq at:
  http://yum.baseurl.org/wiki/Faq

""" % (sys.exc_value, sys.version)
    sys.exit(1)

sys.path.insert(0, '/usr/share/yum-cli')
try:
    import yummain
    yummain.user_main(sys.argv[1:], exit_code=True)
except KeyboardInterrupt, e:
    print >> sys.stderr, "\n\nExiting on user cancel."
    sys.exit(1)

centos8.5.2

#!/usr/libexec/platform-python
# The dnf executable script.
#
# Copyright (C) 2012-2016 Red Hat, Inc.
#
# This copyrighted material is made available to anyone wishing to use,
# modify, copy, or redistribute it subject to the terms and conditions of
# the GNU General Public License v.2, or (at your option) any later version.
# This program is distributed in the hope that it will be useful, but WITHOUT
# ANY WARRANTY expressed or implied, including the implied warranties of
# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General
# Public License for more details.  You should have received a copy of the
# GNU General Public License along with this program; if not, write to the
# Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
# 02110-1301, USA.  Any Red Hat trademarks that are incorporated in the
# source code or documentation are not subject to the GNU General Public
# License and may only be used or replicated with the express permission of
# Red Hat, Inc.
#

from __future__ import unicode_literals
import sys


def suppress_keyboard_interrupt_message():
    """Prevent unsightly KeyboardInterrupt tracebacks.

    Nothing will be printed to the terminal after an uncaught
    :class:`exceptions.KeyboardInterrupt`.

    """
    old_excepthook = sys.excepthook

    def new_hook(type, value, traceback):
        if type != KeyboardInterrupt:
            old_excepthook(type, value, traceback)
        else:
            pass

    sys.excepthook = new_hook


# do this ASAP to prevent tracebacks after ^C during imports
suppress_keyboard_interrupt_message()

if __name__ != "__main__":
    sys.stderr.write('The executable DNF module must not be imported.')
    sys.exit(1)

here = sys.path[0]
if here != '/usr/bin':
    # git checkout
    import os
    dnf_toplevel = os.path.dirname(here)
    sys.path[0] = dnf_toplevel

from dnf.cli import main
main.user_main(sys.argv[1:], exit_code=True)

3.查看文件第一行的python软连接指向

ls -lha /usr/bin/python

4.输出结果

lrwxrwxrwx 1 root root 7 7月  27 12:01 /usr/bin/python -> python2

5.从输出的结果可以看到当前yum依赖的python版本，切不可一些和更改引用关系