Python version manage

• pyenv
  • installation
  • problems
• python-is-python3

pyenv

pyenv’s installation refer to pyenv homepage.
if your network is not good, you can use gitee, clone reporitory to ~/.pyenv and edit your ~/.bashrc:

pyenv可在一台机器上安装不同版本的 python.
安后可以在当前目录或者全局设置不同的 python 版本:

# 列出所有python版本
pvenv versions
# 全局切换到version版本
pyenv global <version>
# 当前路径切换到version版本
pyenv local <version>
# list all python versions
Pyenv install -l

installation

如果网络不好, 可以用克隆gitee 仓库到~/.pyenv目录:

git clone https://gitee.com/mirrors/pyenv.git ~/.pyenv

然后往~/.bashrc添加内容, 可以用命令行添加:

echo 'export PYENV_ROOT="$HOME/.pyenv"' >> ~/.bashrc
echo 'command -v pyenv >/dev/null || export PATH="$PYENV_ROOT/bin:$PATH"' >> ~/.bashrc
echo 'eval "$(pyenv init -)"' >> ~/.bashrc

problems

1. install very slow

   pyenv install <version> may very slow and fail eventually, we can download the .tar file manually and put it in the ~/.pyenv/cache folder, then run pyenv install <version> again.
   donwload link: https://www.python.org/ftp/python/
   if ~/.pyenv/cache directory not exist, create it manually.
   or use this command, replace 2.7.6 with your version:

   $ export v=3.8.10; wget https://registry.npmmirror.com/-/binary/python/$v/Python-$v.tar.xz -P ~/.pyenv/cache/; ~/.pyenv/bin/pyenv install $v
   

2. install error

   your build environment need some packages, see: https://github.com/pyenv/pyenv/wiki#suggested-build-environment
   in ubuntu, execute this command:

   sudo apt update; sudo apt install build-essential libssl-dev zlib1g-dev \
   libbz2-dev libreadline-dev libsqlite3-dev curl \
   libncursesw5-dev xz-utils tk-dev libxml2-dev libxmlsec1-dev libffi-dev liblzma-dev
   

python-is-python3

In Ubuntu 20, the default Python version is 3.8.10, not supporting Python2, entering Python Shell is to enter python3, Python is an invalid command. how to alias python to python3?
we can use alias python=python3 to alias python to python3, add this line to ~/.bashrc to make it permanent.
another solution is install python-is-python3:

 sudo apt install python-is-python3

https://askubuntu.com/questions/320996/how-to-make-python-program-command-execute-python-3