問題

• 在jupyter notebook中將kernel從python3切換到python2時，出現Could not find a kernel matching Python 2. Please select a kernel的錯誤

解決方法

• 檢視已有的ipykernel環境
  jupyter kernelspec list
  如下圖所示，表明python3的ipython核心已安裝

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

• 安裝python2環境
  conda create --name pythonn27 python=2.7
• 切換python環境
  source activate python27
• 安裝ipython核心
  conda install ipykernel
• 配置核心
  python -m ipykernel install --user
• 檢視核心檔案指向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}"
 ]
}