更換python版本後出現 No module named "apt_pkg"

python版本: 默認版本原來是python2.7,  先裝了python3.5=python3.5.3 , 後又裝了python3.6=python3.6.1

將默認版本改爲python3.6後就出現No module named "apt_pkg"的問題,按照如下方式可解決：

$ sudo apt-get remove --purge python-apt
$ sudo apt-get install python-apt -f
$ sudo find / -name "apt_pkg.cpython-35m-x86_64-linux-gnu.so"
$ cd /usr/lib/python3/dist-packages/
$ sudo cp apt_pkg.cpython-35m-x86_64-linux-gnu.so apt_pkg.cpython-36m-x86_64-linux-gnu.so