问题

• 在jupyter notebook中将kernel从python3切换到python2时，出现Could not find a kernel matching Python 2. Please select a kernel的错误

解决方法

• 查看已有的ipykernel环境
  jupyter kernelspec list
  如下图所示，表明python3的ipython内核已安装

Available kernels:
  python3    /home/ozh/.local/share/jupyter/kernels/python3

• 安装python2环境
  conda create --name pythonn27 python=2.7
• 切换python环境
  source activate python27
• 安装ipython内核
  conda install ipykernel
• 配置内核
  python -m ipykernel install --user
• 查看内核文件指向python版本
  位置：~/.local/share/jupyter/kernels/python2/kernel.json

{
 "display_name": "Python 2",
 "language": "python",
 "argv": [
  "/home/ozh/anaconda3/envs/python27/bin/python",
  "-m",
  "ipykernel_launcher",
  "-f",
  "{connection_file}"
 ]
}