在樹莓派中以 python 指令啟動 python3 環境的方法

樹莓派或其他 Linux 作業系統通常預載 Python 2 與 Python 3, 且把 python 指令預設給了 Python 2 而不是 Python 3, 由於現在 Python 3 已成為主流, 每次在樹莓派要進入 Python 3 的 IDLE 環境都因為習慣直接打 python 而進入預設的 Python 2 環境, 必須 exit() 後再輸入 python3 指令, 要怎樣才能讓 python 指令直接啟動 Python 3 環境呢? 很簡單, 只要修改 ~/.bashrc 這個檔案, 在裡面添加下面這一列別名應對資料即可 :

alias python=python 3   

注意, ~/.bashrc 這個檔案是系統檔, 必須用 sudo 權限才能存取. 

首先用 cat 顯示此檔案之內容 :

pi@raspberrypi:~ $ sudo cat ~/.bashrc    

# ~/.bashrc: executed by bash(1) for non-login shells.

# see /usr/share/doc/bash/examples/startup-files (in the package bash-doc)

# for examples

# If not running interactively, don't do anything

case $- in

    *i*) ;;

      *) return;;

esac

# don't put duplicate lines or lines starting with space in the history.

# See bash(1) for more options

HISTCONTROL=ignoreboth

# append to the history file, don't overwrite it

shopt -s histappend

# for setting history length see HISTSIZE and HISTFILESIZE in bash(1)

HISTSIZE=1000

HISTFILESIZE=2000

# check the window size after each command and, if necessary,

# update the values of LINES and COLUMNS.

shopt -s checkwinsize

# If set, the pattern "**" used in a pathname expansion context will

# match all files and zero or more directories and subdirectories.

#shopt -s globstar

# make less more friendly for non-text input files, see lesspipe(1)

#[ -x /usr/bin/lesspipe ] && eval "$(SHELL=/bin/sh lesspipe)"

# set variable identifying the chroot you work in (used in the prompt below)

if [ -z "${debian_chroot:-}" ] && [ -r /etc/debian_chroot ]; then

    debian_chroot=$(cat /etc/debian_chroot)

fi

# set a fancy prompt (non-color, unless we know we "want" color)

case "$TERM" in

    xterm-color|*-256color) color_prompt=yes;;

esac

# uncomment for a colored prompt, if the terminal has the capability; turned

# off by default to not distract the user: the focus in a terminal window

# should be on the output of commands, not on the prompt

force_color_prompt=yes

if [ -n "$force_color_prompt" ]; then

    if [ -x /usr/bin/tput ] && tput setaf 1 >&/dev/null; then

        # We have color support; assume it's compliant with Ecma-48

        # (ISO/IEC-6429). (Lack of such support is extremely rare, and such

        # a case would tend to support setf rather than setaf.)

        color_prompt=yes

    else

        color_prompt=

    fi

fi

if [ "$color_prompt" = yes ]; then

    PS1='${debian_chroot:+($debian_chroot)}\[\033[01;32m\]\u@\h\[\033[00m\]:\[\033[01;34m\]\w \$\[\033[00m\] '

else

    PS1='${debian_chroot:+($debian_chroot)}\u@\h:\w\$ '

fi

unset color_prompt force_color_prompt

# If this is an xterm set the title to user@host:dir

case "$TERM" in

xterm*|rxvt*)

    PS1="\[\e]0;${debian_chroot:+($debian_chroot)}\u@\h: \w\a\]$PS1"

    ;;

*)

    ;;

esac

# enable color support of ls and also add handy aliases

if [ -x /usr/bin/dircolors ]; then

    test -r ~/.dircolors && eval "$(dircolors -b ~/.dircolors)" || eval "$(dircolors -b)"

    alias ls='ls --color=auto'

    #alias dir='dir --color=auto'

    #alias vdir='vdir --color=auto'

    alias grep='grep --color=auto'

    alias fgrep='fgrep --color=auto'

    alias egrep='egrep --color=auto'

fi

# colored GCC warnings and errors

#export GCC_COLORS='error=01;31:warning=01;35:note=01;36:caret=01;32:locus=01:quote=01'

# some more ls aliases

#alias ll='ls -l'

#alias la='ls -A'

#alias l='ls -CF'

# Alias definitions.

# You may want to put all your additions into a separate file like

# ~/.bash_aliases, instead of adding them here directly.

# See /usr/share/doc/bash-doc/examples in the bash-doc package.

if [ -f ~/.bash_aliases ]; then

    . ~/.bash_aliases

fi

# enable programmable completion features (you don't need to enable

# this, if it's already enabled in /etc/bash.bashrc and /etc/profile

# sources /etc/bash.bashrc).

if ! shopt -oq posix; then

  if [ -f /usr/share/bash-completion/bash_completion ]; then

    . /usr/share/bash-completion/bash_completion

  elif [ -f /etc/bash_completion ]; then

    . /etc/bash_completion

  fi

fi

只要用 nano 開啟此檔案 : 

pi@raspberrypi:~ $ sudo nano ~/.bashrc    

然後在 "some more aliases" 這一列底下添加下列指令即可 : 

alias python=python 3