Linux學習5-CentOS安裝Python3.6環境和pip3

前言

centos7 自帶有 python，但是卻是 python2 版本的 python，如果你想安裝個python3怎么辦呢？
如果直接刪除python2的話，可能會引起其他的問題，因為有些東西是依賴python2的，最好的解決辦法是python3和python2共存，新安裝一個python3的環境。

python2

先找到系統的python安裝在哪個目錄，查看對應版本號和相關安裝包
cd / 先回到根目錄
whereis python 查看python所在目錄/usr/bin
cd /usr/bin 切到python目錄
ll python* 查看python開頭的相關文件詳情

[root@yoyo /]# cd /
[root@yoyo /]#  whereis python
python: /usr/bin/python /usr/bin/python2.7 /usr/lib/python2.7 /usr/lib64/python2.7 /etc/python /usr/include/python2.7 /usr/share/man/man1/python.1.gz
[root@yoyo /]# cd /usr/bin
[root@yoyo bin]# ll python*
lrwxrwxrwx. 1 root root    7 Oct 15  2017 python -> python2
lrwxrwxrwx. 1 root root    9 Oct 15  2017 python2 -> python2.7
-rwxr-xr-x. 1 root root 7136 Aug  4  2017 python2.7
[root@yoyo bin]# 

從查看的結果可以看到python指向的是python2 ，python2指向的是python2.7。那也就是在控制台輸入python、python2、python2.7都是運行python2.7

如果我們安裝一個python3.6的環境，讓python3指向3.6， python2指向python2.7, 那就可以完美的共存了

yum安裝依賴

先安裝相關依賴

yum -y install zlib-devel bzip2-devel openssl-devel ncurses-devel sqlite-devel readline-devel tk-devel gdbm-devel db4-devel libpcap-devel xz-devel mysql-devel

安裝python3

從python安裝包的歷史版本中https://www.python.org/ftp/python/，找到需要的安裝包，比如我這里選3.6.8版本

從眾多的包里面找到Python-3.6.8.tgz包，那么下載地址拼接下就是：https://www.python.org/ftp/python/3.6.8/Python-3.6.8.tgz

在Centos 7系統里面新建一個目錄，用於存放下載的python3安裝包，比如： /root/python36

[root@yoyo ~]# mkdir /root/python36

cd到 root/pyrhon36目錄，用wget下載3.6.8安裝包

[root@yoyo python36]# wget https://www.python.org/ftp/python/3.6.8/Python-3.6.8.tgz

[root@yoyo~]# cd /root/pyrhon36
[root@yoyo python3]# wget https://www.python.org/ftp/python/3.6.8/Python-3.6.8.tgz
--2018-12-29 13:37:12--  https://www.python.org/ftp/python/3.6.8/Python-3.6.8.tgz
Resolving www.python.org (www.python.org)... 151.101.108.223, 2a04:4e42:1a::223
Connecting to www.python.org (www.python.org)|151.101.108.223|:443... connected.
HTTP request sent, awaiting response... 200 OK
Length: 23010188 (22M) [application/octet-stream]
Saving to: ‘Python-3.6.8.tgz’

100%[===============================================================================>] 23,010,188  14.2MB/s   in 1.5s   

2018-12-29 13:37:14 (14.2 MB/s) - ‘Python-3.6.8.tgz’ saved [23010188/23010188]

[root@yoyo python36]# 

等待下載完成之后會在當前目錄下出現一個tgz包，tar命令解壓這個包到當前目錄就可以

[root@yoyo python36]# tar -xvf Python-3.6.8.tgz
[root@yoyo python36]# ll
total 22476
drwxr-xr-x 17  501  501     4096 Dec 24 11:01 Python-3.6.8
-rw-r--r--  1 root root 23010188 Dec 24 11:01 Python-3.6.8.tgz

解壓完之后需要編譯Python-3.6.8包下的文件，先cd過去執行完這句命令之后，把python的安裝目錄指定一下，這樣的話，里面的一些bin目錄、lib目錄就都會存放在這個目錄下面。
如果不指定這個安裝目錄的話，最后python的安裝文件將分散到linux的默認目錄，不在一塊。我們指定安裝目錄，以后卸載的話直接刪除目錄就可以干凈卸載了。

[root@yoyo python36]# cd Python-3.6.8
[root@yoyo Python-3.6.8]# ./configure --prefix=/root/python36

在當前目錄root/pyrhon36/Python-3.6.8執行make，執行完之后，接着輸入make install

[root@yoyo Python-3.6.8]# make

[root@yoyo Python-3.6.8]# make install

耐心等待，喝杯咖啡就安裝完成就行了，時間會有點長。

添加軟鏈接

由於系統默認的python是指向python2，這里執行把新安裝的python3.6指向給/usr/bin/python3就可以了

[root@yoyo bin]# ln -s  /root/python36/bin/python3.6 /usr/bin/python3
[root@yoyo bin]# python3 -V
Python 3.6.8
[root@yoyo bin]# python3
Python 3.6.8 (default, Dec 29 2018, 13:48:00) 
[GCC 4.8.5 20150623 (Red Hat 4.8.5-16)] on linux
Type "help", "copyright", "credits" or "license" for more information.
>>> exit()
[root@yoyo bin]# 

輸入python3 -V可以看到版本號，這樣系統默認的就是python3.6.8版本了，如果想用python2.7版本，直接輸入python2就可以了

[root@yoyo bin]# python2
Python 2.7.5 (default, Aug  4 2017, 00:39:18) 
[GCC 4.8.5 20150623 (Red Hat 4.8.5-16)] on linux2
Type "help", "copyright", "credits" or "license" for more information.
>>> exit()

pip環境

python3安裝完成之后，如果想用pip安裝一些第三方包，系統會默認安裝到python2的環境里面。
添加pip3的軟鏈接，這樣輸入pip3 install 就能把安裝包安裝到python3的環境了。

[root@yoyo bin]# ln -s /root/python36/bin/pip3  /usr/bin/pip3
[root@yoyo bin]# pip3 -V
pip 19.2.3 from /usr/local/python3/lib/python3.6/site-packages/pip (python 3.6)
[root@yoyo bin]# pip2 -V
pip 18.1 from /usr/lib/python2.7/site-packages/pip (python 2.7)
[root@yoyo bin]# ll pip*
lrwxrwxrwx 1 root root  27 Jan  2 16:47 pip3 -> /usr/local/python3/bin/pip3
-rwxr-xr-x 1 root root 216 Jan  2 11:05 pip2
-rwxr-xr-x 1 root root 216 Jan  2 11:05 pip2.7
-rwxr-xr-x 1 root root 232 Jan  2 16:53 pip.bak

如果要安裝python3的第三方包，那就輸入pip3 install xx包名

[root@yoyo bin]# pip3 install requests
Looking in indexes: http://mirrors.aliyun.com/pypi/simple/
Collecting requests
  Downloading http://mirrors.aliyun.com/pypi/packages/7d/e3/20f3d364d6c8e5d2353c72a67778eb189176f08e873c9900e10c0287b84b/requests-2.21.0-py2.py3-none-any.whl (57kB)
    100% |████████████████████████████████| 61kB 2.2MB/s 
Requirement already satisfied: idna<2.9,>=2.5 in /usr/local/python3/lib/python3.6/site-packages (from requests) (2.8)
Requirement already satisfied: certifi>=2017.4.17 in /usr/local/python3/lib/python3.6/site-packages (from requests) (2018.11.29)
Requirement already satisfied: chardet<3.1.0,>=3.0.2 in /usr/local/python3/lib/python3.6/site-packages (from requests) (3.0.4)
Requirement already satisfied: urllib3<1.25,>=1.21.1 in /usr/local/python3/lib/python3.6/site-packages (from requests) (1.24.1)
Installing collected packages: requests
Successfully installed requests-2.21.0
[root@yoyo bin]# python 
Python 3.6.8 (default, Jan  2 2019, 16:43:17) 
[GCC 4.8.5 20150623 (Red Hat 4.8.5-16)] on linux
Type "help", "copyright", "credits" or "license" for more information.
>>> import requests
>>> exit()
[root@yoyo bin]# 

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