Conda虚拟环境嵌套导致的一系列路径问题
最近在linux上是用conda虚拟环境出现很多问题。
比如使用conda activate py3.7激活环境后发现python搜索路径依然是默认路径：
In [1]: import sys In [2]: sys.path Out[2]: ['/home/sherry/anaconda3/bin', '/home/sherry', '/home/sherry/git/models/research', '/home/sherry/git/models/research/slim', '/home/sherry/anaconda3/lib/python37.zip', '/home/sherry/anaconda3/lib/python3.7', '/home/sherry/anaconda3/lib/python3.7/lib-dynload', '', '/home/sherry/.local/lib/python3.7/site-packages', '/home/sherry/anaconda3/lib/python3.7/site-packages', '/home/sherry/anaconda3/lib/python3.7/site-packages/IPython/extensions', '/home/sherry/.ipython']
同时pip的安装路径也不太对，问题同这篇文章，但是后来里面的方法也失效了，不得不在.bashrc.sh里用alias指定 pip path
(py3.7) sherry@lambda-1:~$ which pip /home/sherry/anaconda3/envs/py3.7/bin/pip (py3.7) sherry@lambda-1:~$ type pip pip is /home/sherry/anaconda3/bin/pip
alias pip=/home/sherry/anaconda3/envs/py3.7/bin/pip
参考这篇文章之后发现，问题可能在于环境嵌套。
每次登陆进linux系统后默认进入base环境，再用conda activate激活虚拟环境，会导致发生环境嵌套，具体可以通过conda info中的shell level参数查看：
(py3.7) sherry@lambda-1:~$ conda info active environment : py3.7 active env location : /home/sherry/anaconda3/envs/py3.7 shell level : 2 user config file : /home/sherry/.condarc populated config files : conda version : 4.8.3 conda-build version : 3.18.11 python version : 3.7.7.final.0 virtual packages : __cuda=11.0 __glibc=2.27 base environment : /home/sherry/anaconda3 (writable) channel URLs : https://repo.anaconda.com/pkgs/main/linux-64 https://repo.anaconda.com/pkgs/main/noarch https://repo.anaconda.com/pkgs/r/linux-64 https://repo.anaconda.com/pkgs/r/noarch package cache : /home/sherry/anaconda3/pkgs /home/sherry/.conda/pkgs envs directories : /home/sherry/anaconda3/envs /home/sherry/.conda/envs platform : linux-64 user-agent : conda/4.8.3 requests/2.23.0 CPython/3.7.7 Linux/5.4.0-42-generic ubuntu/18.04.3 glibc/2.27 UID:GID : 1004:1022 netrc file : None offline mode : False
这里shell level是2说明发生嵌套，关于嵌套的更多说明如下：
当已经激活某个环境时，再次 conda activate envname 将发生环境嵌套，而不是切换。
多个环境嵌套时，软件包可能产生异常行为。
Python 需格外小心！若最内层环境没有安装 Python，所有与 Python 有关的程序（尤其是 pip ）将逐层向外 fallback 直至 base，很容易造成污染。
可通过 conda info 的 shell level 来检查嵌套情况。
如非特别必要，不建议使用环境嵌套。
默认允许 2 层环境嵌套，可通过 conda config --set max_shlvl number 调至更高或将该特性关闭。
解决方法先用conda deactivate退出base，再激活py3.7，python搜索路径即可恢复正常。
(base) sherry@lambda-1:~$ conda deactivate sherry@lambda-1:~$ conda activate py3.7 (py3.7) sherry@lambda-1:~$ which pip /home/sherry/anaconda3/envs/py3.7/bin/pip (py3.7) sherry@lambda-1:~$ type pip pip is /home/sherry/anaconda3/envs/py3.7/bin/pip (py3.7) sherry@lambda-1:~$ conda info active environment : py3.7 active env location : /home/sherry/anaconda3/envs/py3.7 shell level : 1 user config file : /home/sherry/.condarc populated config files : conda version : 4.8.3 conda-build version : 3.18.11 python version : 3.7.7.final.0 virtual packages : __cuda=11.0 __glibc=2.27 base environment : /home/sherry/anaconda3 (writable) channel URLs : https://repo.anaconda.com/pkgs/main/linux-64 https://repo.anaconda.com/pkgs/main/noarch https://repo.anaconda.com/pkgs/r/linux-64 https://repo.anaconda.com/pkgs/r/noarch package cache : /home/sherry/anaconda3/pkgs /home/sherry/.conda/pkgs envs directories : /home/sherry/anaconda3/envs /home/sherry/.conda/envs platform : linux-64 user-agent : conda/4.8.3 requests/2.23.0 CPython/3.7.7 Linux/5.4.0-42-generic ubuntu/18.04.3 glibc/2.27 UID:GID : 1004:1022 netrc file : None offline mode : False
In [1]: import sys In [2]: sys.path Out[2]: ['/home/sherry/anaconda3/envs/py3.7/bin', '/home/sherry', '/home/sherry/git/models/research', '/home/sherry/git/models/research/slim', '/home/sherry/anaconda3/envs/py3.7/lib/python37.zip', '/home/sherry/anaconda3/envs/py3.7/lib/python3.7', '/home/sherry/anaconda3/envs/py3.7/lib/python3.7/lib-dynload', '', '/home/sherry/.local/lib/python3.7/site-packages', '/home/sherry/anaconda3/envs/py3.7/lib/python3.7/site-packages', '/home/sherry/anaconda3/envs/py3.7/lib/python3.7/site-packages/IPython/extensions', '/home/sherry/.ipython']
