在linux下修改環境變量，切換不一樣版本的python的path

這個Linux系統下原本裝了python2，並且是好幾個。還裝了anaconda，自帶python3。個人目的是想讓python環境變量默認使用python3。python

查看當前python版本：apache

[liusiyi@localhost ~]$ python --version
Python 2.7.5

用which 看一下當前使用的python的路徑：bash

[liusiyi@localhost ~]$ which python
/usr/bin/python

用whereis 確認全部python路徑（但這個不全，由於沒有anaconda）：app

[liusiyi@localhost ~]$ whereis python
python: /usr/bin/python /usr/bin/python2.7 /usr/bin/python2.7-config /usr/lib/python2.7 /usr/lib64/python2.7 /etc/python /usr/include/python2.7 /usr/share/man/man1/python.1.gz

改用echo $PATH再次確認（這裏也沒包含anaconda）：python2.7

[liusiyi@localhost ~]$ echo $PATH
/appcom/kylin/bin:/appcom/hadoop/bin:/appcom/hadoop/sbin:/usr/lib/jdk/bin:/usr/local/bin:/usr/bin:/usr/local/sbin:/usr/sbin:/home/shijuan355/bin:/appcom/hadoop/bin:/appcom/hadoop/sbin:/home/shijuan355/bin:/appcom/ganglia/sbin:/appcom/ganglia/bin:/appcom/sqoop/bin:/appcom/hive/bin:/appcom/hbase/bin:/appcom/zookeeper/bin:/appcom/R/bin:/appcom/apache/bin:/appcom/oozie/bin:/appcom/btrace/bin:/appcom/storm/bin:/appcom/rocketmq//bin:/appcom/hbase/bin:/appcom/hbase/sbin:/appcom/R2/bin:/appcom/R3/bin:/appcom/spark/bin:/appcom/spark/sbin:/appcom/kafka/bin:/appcom/flume/bin:/appcom/odpp/bin:

用export PATH=添加python3路徑：oop

[liusiyi@localhost ~]$ export PATH=/appcom/AnacondaInstall/anaconda3/bin:$PATH

這時候用python --version 看仍是Python 2.7.5。由於bash命令export PATH=/appcom/AnacondaInstall/anaconda3/bin:$PATH，使PATH自增，既PATH=PATH+"/appcom/AnacondaInstall/anaconda3/bin:"；一般是把這行bash命令寫到末尾。spa

下面採用在~/.bashrc 裏添加一行「export PATH=/appcom/AnacondaInstall/anaconda3/bin:$PATH」的方式，這個只對當前用戶生效，是比較穩妥的作法。.net

修改前的 ~/.bashrc：code

[liusiyi@localhost  ~]$ cat ~/.bashrc
# .bashrc

# Source global definitions
if [ -f /etc/bashrc ]; then
        . /etc/bashrc
fi

# Uncomment the following line if you don't like systemctl's auto-paging feature:
# export SYSTEMD_PAGER=

# User specific aliases and functions

修改後的 ~/.bashrc，最後多了一行：orm

[liusiyi@localhost  ~]$ cat ~/.bashrc
# .bashrc

# Source global definitions
if [ -f /etc/bashrc ]; then
        . /etc/bashrc
fi

# Uncomment the following line if you don't like systemctl's auto-paging feature:
# export SYSTEMD_PAGER=

# User specific aliases and functions
export PATH=/appcom/AnacondaInstall/anaconda3/bin:$PATH

這時候有兩個方法讓這個環境變量生效。一、關閉當前終端窗口，從新打開一個新終端窗口就能生效；二、輸入「source ~/.bashrc」命令，當即生效。

如今再來查看，python3已經成爲默認的環境變量：

[liusiyi@localhost ~]$ which python
/appcom/AnacondaInstall/anaconda3/bin/python

[liusiyi@localhost ~]$ python --version
Python 3.6.3 :: Anaconda, Inc.

還有不少其餘方法能實現不一樣版本的python切換環境變量默認值。不少文章都講過。

python中path路徑的優先匹配順序：https://blog.csdn.net/wangzhaotongalex/article/details/50127431

切換Python2和Python3的4種方法：https://blog.csdn.net/jasonfqw/article/details/72974187