1. 注册google，登录Google Drive, 在My Drive 下新创建一个文件夹作为ipynb 根目录（文件名随意， 后面步骤要用到）， 然后Colab Notebooks新建文件夹放package（文件名随意， 后面步骤也需要用到

2. Open Colab -> create  ipynb

① 挂载google drive以及添加sys path

import os, sys 
# 挂载google drive
from google.colab import drive 
drive.mount('/content/gdrive') 

nb_path = '/content/notebooks'
os.symlink('/content/gdrive/My Drive/Colab Notebooks', nb_path)
sys.path.insert(0, nb_path)  # or append(nb_path)

 ② 安装
!pip install --target=$nb_path <package_name>

# 将安装包安装到指定路径（这里安装到Colab Notebooks/python_package目录下）
# !pip install --target=$nb_path d2l 

3. 以后每新建一个ipynb,粘贴以下代码段至文件开头并运行，即可使用python_package中的模块

import sys
from google.colab import drive
drive.mount('/content/gdrive')
sys.path.insert(0,"/content/gdrive/My Drive/Colab Notebooks/python_package/")

原作者博客：http://profeitm.blogspot.com/2020/12/how-to-permanently-install-module-on.html