conda創建和使用python的虛擬環境

https://uoa-eresearch.github.io/eresearch-cookbook/recipe/2014/11/20/conda/

當我們使用服務器的時候，會存在多個用戶，並且可能系統管理員也安裝了anaconda，這樣python指向的環境有肯能是管理員的目錄，

我們可以通過 conda env list 查看存在的環境，以及當前使用的是哪個環境， 可以根據pytorch的不同版本安裝在相應的環境中，便於適應不同的項目

$conda env list
# conda environments:
#
pytorch1.0               /home/username1/.conda/envs/pytorch1.0
                         /home/username1/anaconda2
base                  *  /home/username2/install/anaconda2

其中星號表示當前使用的環境路徑，我們可以通過以下方式修改

1. 創建虛擬環境

conda create -n env_name python=2.7.14

env_name：要創建的虛擬環境名稱

2. 激活環境

source activate env_name

3. 查看環境

conda env list

顯示結果，當前環境已經變為我們設置的目錄了

# conda environments:
#
pytorch1.0            *  /home/username1/.conda/envs/pytorch1.0
                         /home/username1/anaconda2
base                     /home/username2/install/anaconda2

4. 退出環境

conda deactivate

5. 刪除環境

conda remove -n env_name --all

 注意：win10下cmd或者powershell經常無法激活虛擬環境，即如下錯誤

CommandNotFoundError: Your shell has not been properly configured to use 'conda activate'.
If your shell is Bash or a Bourne variant, enable conda for the current user with

    $ echo ". D:\Anaconda3/etc/profile.d/conda.sh" >> ~/.bashrc

or, for all users, enable conda with

    $ sudo ln -s D:\Anaconda3/etc/profile.d/conda.sh /etc/profile.d/conda.sh

The options above will permanently enable the 'conda' command, but they do NOT
put conda's base (root) environment on PATH.  To do so, run

    $ conda activate

in your terminal, or to put the base environment on PATH permanently, run

    $ echo "conda activate" >> ~/.bashrc

Previous to conda 4.4, the recommended way to activate conda was to modify PATH in
your ~/.bashrc file.  You should manually remove the line that looks like

    export PATH="D:\Anaconda3/bin:$PATH"

^^^ The above line should NO LONGER be in your ~/.bashrc file! ^^^

解決辦法：可以使用anaconda自帶的Anaconda Prompt運行