Preserving Python 2

First, locate the Python installation and back up the Python 2.7 symlink.

# Navigate to home directory and find Python locations
cd ~
whereis python

# Check existing Python symlinks in /usr/bin
cd /usr/bin
ls -l python*

# Back up the python symlink
mv python python.backup

Downloading and Installing Python 3

Download Python 3 from the official Python FTP server: https://www.python.org/ftp/python/

# Create directory for Python 3 and download the source
cd /usr/local
mkdir python3
cd python3
wget https://www.python.org/ftp/python/3.6.8/Python-3.6.8.tgz

# Extract the archive
sudo tar -xvf Python-3.6.8.tgz

# Configure and compile Python 3
cd Python-3.6.8
./configure --prefix=/usr/local/python3
make && sudo make install

If you encounter a zlib error during compilation:

# Restore original Python symlink temporarily
mv /usr/bin/python.backup /usr/bin/python

# Install zlib development libraries
yum install zlib-devel -y

# Re-backup the symlink
mv /usr/bin/python /usr/bin/python.backup

# Retry the compilation
make clean
./configure --prefix=/usr/local/python3
make && sudo make install

Create a symbolic link for Python 3:

ln -s /usr/local/python3/bin/python3 /usr/bin/python

Modiyfing YUM Configuration

YUM depends on Python 2, so update its configuration files:

# Update YUM to use Python 2
sed -i 's#/usr/bin/python#/usr/bin/python2#g' /usr/bin/yum

# Update URL grabber extension
sed -i 's#/usr/bin/python#/usr/bin/python2#g' /usr/libexec/urlgrabber-ext-down

Configuring PIP

Create a symbolic link for pip:

ln -s /usr/local/python3/bin/pip3 /usr/bin/pip

Setting Up PIP Mirror

Configure pip to use a mirrer for faster downloads:

# Create pip configuration directory
mkdir -p ~/.pip
cd ~/.pip

# Create configuration file
cat > pip.conf << 'EOF'
[global]
index-url = http://pypi.douban.com/simple
[install]
use-mirrors = true
mirrors = http://pypi.douban.com/simple/
trusted-host = pypi.douban.com
EOF

For Windows systems, create a pip.ini file at: C:\Users\[Username]\AppData\Roaming\pip\

With the same content as above.

Complete Installation Script

Here's a consolidated script for installing Python 3.6.8:

#!/bin/bash

# Install required dependencies
yum install zlib-devel -y

# Backup original Python symlink
mv /usr/bin/python /usr/bin/python.backup

# Create Python 3 directory
mkdir -p /usr/local/python3
cd /usr/local/python3

# Download and extract Python 3.6.8
wget https://www.python.org/ftp/python/3.6.8/Python-3.6.8.tgz
tar -xf Python-3.6.8.tgz

# Compile and install
cd Python-3.6.8
./configure --prefix=/usr/local/python3
make && sudo make install

# Create symbolic links
ln -sf /usr/local/python3/bin/python3 /usr/bin/python
ln -sf /usr/local/python3/bin/pip3 /usr/bin/pip

# Update YUM configuration
sed -i 's#/usr/bin/python#/usr/bin/python2#g' /usr/bin/yum
sed -i 's#/usr/bin/python#/usr/bin/python2#g' /usr/libexec/urlgrabber-ext-down

# Configure pip mirror
mkdir -p ~/.pip
cat > ~/.pip/pip.conf << 'EOF'
[global]
index-url = http://pypi.douban.com/simple
[install]
use-mirrors = true
mirrors = http://pypi.douban.com/simple/
trusted-host = pypi.douban.com
EOF

# Verify installation
python --version
pip --version