利用.bashrc來動態切換conda2和conda3

需求

最近想要從conda2切換到conda3，但是因為之前的許多應用還是依賴於python2的環境，於是就產生了動態切換conda3的需求

分析

筆者使用的是Ubuntu的環境，並且conda是安裝在用戶目錄下的，也就是/home/user/anaconda2,成功安裝conda3之后，也會在用戶目錄下生成目錄/home/user/anaconda3,於是我想應該只需要動態切換一些環境變量就能實現動態切換了

解決方案

安裝anaconda3

去官方目錄下載最新版本的anaconda3,筆者下載好的文件是：Anaconda3-2019.10-Linux-x86_64.sh, 在終端目錄下運行：

$ bash Anaconda3-2019.10-Linux-x86_64.sh

在安裝的最后一步會提示需不需要運行conda init，這個時候選擇yes

這項功能會在~/.bashrc文件下生成一段shell代碼

# >>> conda initialize >>>
# !! Contents within this block are managed by 'conda init' !!
__conda_setup="$('/home/user/anaconda3/bin/conda' 'shell.bash' 'hook' 2> /dev/null)"
if [ $? -eq 0 ]; then
    eval "$__conda_setup"
else
    if [ -f "/home/user/anaconda3/etc/profile.d/conda.sh" ]; then
# . "/home/user/anaconda3/etc/profile.d/conda.sh"  # commented out by conda initialize
    else
# export PATH="/home/user/anaconda3/bin:$PATH"  # commented out by conda initialize
    fi
fi
unset __conda_setup
# <<< conda initialize <<<

筆者之前安裝的anaconda2生成的代碼是這樣的

# added by Anaconda2 5.3.0 installer
# >>> conda init >>>
# !! Contents within this block are managed by 'conda init' !!
__conda_setup="$(CONDA_REPORT_ERRORS=false '/home/user/anaconda2/bin/conda' shell.bash hook 2> /dev/null)"
if [ $? -eq 0 ]; then
    \eval "$__conda_setup"
else
    if [ -f "/home/user/anaconda2/etc/profile.d/conda.sh" ]; then
# . "/home/user/anaconda2/etc/profile.d/conda.sh"  # commented out by conda initialize
        CONDA_CHANGEPS1=false conda activate base
    else
        \export PATH="/home/user/anaconda2/bin:$PATH"
    fi
fi
unset __conda_setup
# <<< conda init <<<

於是筆者就想能不能把這2段初始化代碼放到shell函數中，然后用一個參數選擇初始化那一段代碼

select_conda() {

    if [ $1 == "conda2" ]
    then
        # added by Anaconda2 5.3.0 installer
        # >>> conda init >>>
        # !! Contents within this block are managed by 'conda init' !!
        __conda_setup="$(CONDA_REPORT_ERRORS=false '/home/user/anaconda2/bin/conda' shell.bash hook 2> /dev/null)"
        if [ $? -eq 0 ]; then
            \eval "$__conda_setup"
        else
            if [ -f "/home/user/anaconda2/etc/profile.d/conda.sh" ]; then
        # . "/home/user/anaconda2/etc/profile.d/conda.sh"  # commented out by conda initialize
                CONDA_CHANGEPS1=false conda activate base
            else
                \export PATH="/home/user/anaconda2/bin:$PATH"
            fi
        fi
        unset __conda_setup
        # <<< conda init <<<
    fi

    if [ $1 == "conda3" ]
    then
        # >>> conda initialize >>>
        # !! Contents within this block are managed by 'conda init' !!
        __conda_setup="$('/home/user/anaconda3/bin/conda' 'shell.bash' 'hook' 2> /dev/null)"
        if [ $? -eq 0 ]; then
            eval "$__conda_setup"
        else
            if [ -f "/home/user/anaconda3/etc/profile.d/conda.sh" ]; then
# . "/home/user/anaconda3/etc/profile.d/conda.sh"  # commented out by conda initialize
            else
# export PATH="/home/user/anaconda3/bin:$PATH"  # commented out by conda initialize
            fi
        fi
        unset __conda_setup
        # <<< conda initialize <<<
    fi

}

測試

當我想要選擇anaconda2的時候，就在~/.bashrc中加上

select_conda "conda2"

重新打開一個終端：

$ python
Python 2.7.12 (default, Oct  8 2019, 14:14:10) 
[GCC 5.4.0 20160609] on linux2
Type "help", "copyright", "credits" or "license" for more information.

當我想要選擇anaconda3的時候，就在~/.bashrc中加上

select_conda "conda3"

終端運行：

$ . ~/.bashrc
$ python
Python 3.7.4 (default, Aug 13 2019, 20:35:49)
[GCC 7.3.0] :: Anaconda, Inc. on linux
Type "help", "copyright", "credits" or "license" for more information.