Coexistence of python2 and python3 under centos7 system

The first step is to check the version number and installation path of Python;

From the above view, we can see that python points to python2 by default, so we don’t change it here and just keep the current state.

Note: (Because there are still many system updates that require the use of pyhton2, such as: Centos7 yum installation and update. Frameworks such as Django now use python3 by default)

The second step is to install the related dependency libraries of python3.

1. Install dependencies that may be used by python3.7 yum -y install openssl-devel bzip2-devel expat-devel gdbm-devel readline-devel sqlite-devel wget
yum -y install zlib-devel bzip2-devel openssl-devel ncurses-devel sqlite-devel readline-devel tk-devel gcc
yum -y install libffi-devel 

2. Download Python 3
cd /tmp/
wget https://www.python.org/ftp/python/3.7.4/Python-3.7.4.tgz

3. Unzip the downloaded compressed package tar -zxvf Python-3.7.4.tgz

4. Configure and compile mkdir /usr/local/python3
cd Python-3.7.4/　
 ./configure --enable-shared --prefix=/usr/local/python3 --enable-optimizations
make
make install

Step 4: After the installation is complete, create a soft link

Later use is to directly enter python and run python2. Enter python3 to run pyhton3.

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

pip3 install --upgrade pip

This step may result in the following error:

Error message:

python3: error while loading shared libraries: libpython3.7m.so.1.0: cannot open shared object file: No such file or directory

Solution: (Enter the installation directory and copy the file)

cd /tmp/Python-3.7.4/
cp libpython3.7m.so.1.0 /usr/local/lib64
cp libpython3.7m.so.1.0 /usr/lib/
cp libpython3.7m.so.1.0 /usr/lib64/ 

Step 5. Complete all installations and create a Python virtual environment for the next update

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