不见了是因为依赖冲突，给卸载掉了吧。  提供一下/var/log/apt/history.log我看看。

Start-Date: 2017-12-20  20:07:35
Commandline: apt-get remove python3
Requested-By: txs (1000)
Remove: python3-pexpect:amd64 (4.2.1-1), python3-defer:amd64 (1.0.6-2), python3-dae:amd64 (1.0.2+r2~a4bf2bd.b3), hplip-data:amd64 (3.17.6+repack0-2deepin), python3-cupshelpers:amd64 (1.5.9-2deepin), python3-notify2:amd64 (0.3-3), gedit:amd64 (3.22.0-1+deepin2), system-config-printer:amd64 (1.5.9-2deepin), python3-olefile:amd64 (0.44-1), printer-driver-m2300w:amd64 (0.51-12+b1), foomatic-db-compressed-ppds:amd64 (20170723-1), python3-xkit:amd64 (0.5.0ubuntu2), deepin-manual:amd64 (1.0.6-1), python3-xlib:amd64 (0.15~rc+nmu1), youdao-dict:amd64 (1.0.8-1), printer-driver-foo2zjs:amd64 (20170320dfsg0-2), printer-driver-postscript-hp:amd64 (3.17.6+repack0-2deepin), python3-urllib3:amd64 (1.19.1-1), python3-aptdaemon.gtk3widgets:amd64 (1.1.1+bzr982-1), dde:amd64 (15.5), python3-reportlab-accel:amd64 (3.4.0-3+b1), python3-gi-cairo:amd64 (3.22.0-2+b1), chrome-dde:amd64 (62.0.3202.62), printer-driver-escpr:amd64 (1.6.13-1), google-chrome-stable:amd64 (63.0.3239.84-1), python3-pyqt5:amd64 (5.6+dfsg-1+b1), sogoupinyin:amd64 (2.2.0.0100), python3-pil:amd64 (4.1.1-3), python3:amd64 (3.5.3-3), printer-driver-pxljr:amd64 (1.4+repack0-4+b2), python3-sip:amd64 (4.18.1+dfsg-2+b1), python3-six:amd64 (1.10.0-4), python3-requests:amd64 (2.12.4-1), python3-cups:amd64 (1.9.73-1+b1), python3-xdg:amd64 (0.25-4), fcitx-sogoupinyin-uk:amd64 (0.1.0), python3-pyqt5.qtwebkit:amd64 (5.6+dfsg-1+b1), libglib2.0-dev-bin:amd64 (2.53.4-3), ubuntu-drivers-common:amd64 (3:0.4.22+deepin), hplip:amd64 (3.17.6+repack0-2deepin), mintdrivers:amd64 (1.3.1-1), printer-driver-dymo:amd64 (1.4.0-6+b1), python3-pyqt5.qtquick:amd64 (5.6+dfsg-1+b1), python3-smbc:amd64 (1.0.15.6-1+b1), gedit-common:amd64 (3.22.0-1+deepin2), libglib2.0-dev:amd64 (2.53.4-3), python3-pkg-resources:amd64 (36.0.1-1), dh-python:amd64 (2.20170125), openprinting-ppds:amd64 (20170723-1), python3-dbus:amd64 (1.2.4-1+b2), python3-jieba:amd64 (0.36-2), python3-cairo:amd64 (1.10.0+dfsg-5+b3), python3-aptdaemon:amd64 (1.1.1+bzr982-1), lsb-release:amd64 (9.20161125), python3-gi:amd64 (3.22.0-2+b1), python3-ptyprocess:amd64 (0.5.2-1), aptdaemon:amd64 (1.1.1+bzr982-1), system-config-printer-common:amd64 (1.5.9-2deepin), python3-reportlab:amd64 (3.4.0-3), libimobiledevice-dev:amd64 (1.2.0+dfsg-4deepin), printer-driver-ptouch:amd64 (1.4.2-2+b1), python3-lxml:amd64 (3.8.0-1+b1), python3-chardet:amd64 (3.0.4-1), printer-driver-foo2zjs-common:amd64 (20170320dfsg0-2), python3-pyqt5.qtmultimedia:amd64 (5.6+dfsg-1+b1), python3-apt:amd64 (1.4.0~beta3+b1)
End-Date: 2017-12-20  20:07:51

Start-Date: 2017-12-21  09:43:42
Commandline: apt-get -y -o APT::Status-Fd=3 -c /var/lib/lastore/apt.conf -f install -- chrome-dde
Install: chrome-dde:amd64 (62.0.3202.62), google-chrome-stable:amd64 (63.0.3239.84-1, automatic), python3:amd64 (3.5.3-3, automatic), dh-python:amd64 (2.20170125, automatic), lsb-release:amd64 (9.20161125, automatic)
End-Date: 2017-12-21  09:43:47

Start-Date: 2017-12-21  10:36:15
Commandline: apt-get -y -o APT::Status-Fd=3 -c /var/lib/lastore/apt.conf -f install -- sogoupinyin
Install: sogoupinyin:amd64 (2.2.0.0100)
End-Date: 2017-12-21  10:36:20

我后来又安装了python3.6.4,在user/bin 里面创建了个叫python3.6的软连接,然后在pycharm里可以正常使用python3.6.4跑代码

系统的python千万不要乱动，python属于linux系统的底层依赖，很多系统级的服务都使用python编写，乱改系统python很容易造成系统崩溃。

如果你非要选择一个和系统版本不一致的python，建议使用conda

其实你可以添加一个Python的ppa，把系统的python3给升级上去，这样稳妥一些，只要注意不会卸载什么就行。

我是不是,需要再重新装一遍系统了......

不用啊，降级python，再把那些卸载的软件给装回来就行了。

我是自定义目录源码安装的py36，自己装的软件都在/usr/local里，py36提示让运行[./configure --## ## enable-optimizations]的时候不运行，然后自己做一个py36的软链和自带的并存就可以