CentOS Python安裝更新與升級

Checking Current Python Version
Before updating Python, verify the installed versions on your CentOS system using:

python --version  # Checks Python 2.x (if installed)
python3 --version # Checks Python 3.x (default in CentOS 7+)

This helps determine whether an update is needed and identifies the current default version.

Updating System Packages
Ensure your system’s package index is up-to-date to avoid compatibility issues during Python installation:

sudo yum update -y  # For CentOS 7
sudo dnf update -y  # For CentOS 8+

This step installs the latest security patches and dependencies required for Python.

Installing/Updating Python via Yum/DNF (Recommended for Stability)
The easiest way to install or update Python is using CentOS’ native package manager. This method ensures compatibility with system tools but may not provide the latest Python versions.

• For CentOS 7:

  sudo yum install epel-release -y  # Enable EPEL for additional packages
  sudo yum install python3 -y       # Installs/updates Python 3 (e.g., 3.6)
  

• For CentOS 8+:

  sudo dnf install epel-release -y
  sudo dnf install python3 -y       # Installs/updates Python 3 (e.g., 3.9)
  

After installation, verify the version:

python3 --version

To set Python 3 as the default python command (optional), use:

sudo alternatives --install /usr/bin/python python /usr/bin/python3 1
sudo alternatives --config python     # Select Python 3 from the list

Installing/Updating Python from Source (For Latest Versions)
If you need a specific Python version (e.g., 3.11) or custom optimizations, compile from source. This method requires manual dependency management but offers flexibility.

• Install Dependencies:

  sudo yum groupinstall "Development Tools" -y  # Compilers, make, etc.
  sudo yum install openssl-devel bzip2-devel libffi-devel wget -y  # Python build dependencies
  

• Download and Extract Source Code:
  Visit the Python official website to get the latest version link. For example, for Python 3.11.6:

  cd /usr/src  # Recommended directory for source files
  sudo wget https://www.python.org/ftp/python/3.11.6/Python-3.11.6.tgz
  sudo tar xzf Python-3.11.6.tgz
  cd Python-3.11.6
  

• Configure, Compile, and Install:

  sudo ./configure --enable-optimizations  # Optimizes Python performance
  sudo make altinstall                     # Avoids overwriting system Python (installs as python3.11)
  

  Note: Use altinstall instead of install to prevent conflicts with the system’s default Python.
• Verify Installation:

  python3.11 --version  # Replace with your installed version
  

Managing Multiple Python Versions with pyenv
For users needing multiple Python versions (e.g., 3.8 for legacy apps, 3.11 for new projects), pyenv is a powerful tool. It allows easy switching between versions without affecting system stability.

• Install pyenv:

  curl https://pyenv.run | bash
  

  Add the following to your ~/.bashrc (or ~/.zshrc) to enable pyenv:

  export PATH="$HOME/.pyenv/bin:$PATH"
  eval "$(pyenv init --path)"
  eval "$(pyenv virtualenv-init -)"
  

  Reload the shell:

  source ~/.bashrc
  

• Install and Set Python Version:

  pyenv install 3.11.6  # Installs Python 3.11.6
  pyenv global 3.11.6   # Sets as the default Python for the user
  

  Verify with:

  python --version  # Should show 3.11.6
  

  To install a specific version for a project (without changing the global default):

  cd /path/to/project
  pyenv local 3.8.12  # Creates a .python-version file for the project
  

Creating Virtual Environments (Best Practice for Isolation)
After updating Python, always use virtual environments to isolate project dependencies and avoid conflicts.

• Install venv Module (comes with Python 3.3+):

  sudo yum install python3-venv -y
  

• Create and Activate a Virtual Environment:

  python3 -m venv myenv  # Creates a virtual environment named 'myenv'
  source myenv/bin/activate  # Activates the environment (changes prompt to (myenv))
  

  Once activated, install packages using pip (e.g., pip install numpy). Deactivate with deactivate when done.

Key Notes for a Safe Update

• Backup Data: Before making system-level changes, back up important files (e.g., /etc, /home).
• Check Compatibility: Ensure your applications (e.g., web servers, scripts) support the new Python version. Test in a staging environment first.
• Avoid Overwriting System Python: CentOS relies on Python 2/3 for system tools (e.g., yum). Always use altinstall or tools like pyenv to prevent breakage.