Install Python 3.9.9 on Centos7

1. Download necessary dependency package

yum install -y libffi-devel zlib-devel bzip2-devel openssl-devel ncurses-devel sqlite-devel readline-devel tk-devel zlib gcc make libpcap-devel xz-devel gdbm-devel libxslt-devel libxml2-devel

yum install -y zlib-devel bzip2-devel openssl-devel ncurses-devel sqlite-devel zlib* libffi-devel readline-devel tk-devel

2. Download python3.9.9

wget https://www.python.org/ftp/python/3.9.9/Python-3.9.9.tgz

If it posted error about wget, most probably wget has not been installed yet.

yum install wget

3. Uncompressed python3.9.9 and make install

tar -zxvf Python-3.9.9.tgz
cd Python-3.9.9
./configure
make&&make install

4. configure Env Varables so that python2/python3, pip can be distinguished

mv /usr/bin/python /usr/bin/python.bak   #删除以前python2.7的软连接
ln -s /usr/local/bin/python3 /usr/bin/python
mv /usr/bin/pip /usr/bin/pip.bak (如果报错说没有pip直接跳过）
以下为没有此文件或目录报错

ln -s /usr/local/bin/pip3 /usr/bin/pip

5. Confirm if Python and Pip have been installed successfully

python
exit()
pip -V

6. Install virtualenv and virtualenvwrapper

Installation Env.: Centos7

Reference: https://www.cnblogs.com/hszstudypy/p/11510933.html

a. Install virtualenv

pip3 install virtualenv

b. Install virtualenvwrapper

pip3 install virtualenvwrapper

c. Configure global varables

(1) find / -name virtualenvwrapper.sh

WORKON_HOME=~/Envs # Set virtualenv management directory, all virtual env. you will download in futre, will be stored here

(2) vi ~/.bashrc (Add contents below)

VIRTUALENVWRAPPER_PYTHON=/usr/local/bin/python3 #Assign python 解释器的本体(注意此路径随不同的linux环境改变而改变)

export WORKON_HOME=~/Envs
export VIRTUALENVWRAPPER_VIRTUALENV=/usr/local/bin/virtualenv
export VIRTUALENVWRAPPER_VIRTUALENV=/usr/local/bin/virtualenv
source /usr/local/bin/virtualenvwrapper.sh

(3) execute source ~/.bashrc and make it work

source ~/.bashrc
reboot 

(4) virtualenvwrapper instructions

1) Create virtual Environment

mkvirtualenv demo3

2) Look up virtual env.s

lsvirtualenv or workon

3) Start or switch virtual env.s

workon [env. name]

4) Exit out virtual env.s

deactivate

5) Delete virtual env.s

rmvirtualenv [Virtual env. name]

6) Look up virtual env.s packages

pip list