Flask

For develop some internal tools.

reference docs

• https://flask.palletsprojects.com/en/1.1.x/
• https://flask-appbuilder.readthedocs.io/en/latest/intro.html
• https://github.com/luhuisicnu/The-Flask-Mega-Tutorial-zh 2017年新版The Flask Mega-Tutorial教程

pyvenv

Recommend to use pyvenv to develop flask, easy to manage the python version and packages

• https://docs.python.org/3/library/venv.html#module-venv

python3 -m venv /path/to/new/virtual/environment

source /path/to/new/virtual/environment

install flask

• https://flask-appbuilder.readthedocs.io/en/latest/installation.html#
• https://flask.palletsprojects.com/en/1.1.x/installation/#installation

# under virtual env
pip install Flask

pip install flask-appbuilder

flask fab create-app

flask run

SQLAlchemy

• English Documentation https://docs.sqlalchemy.org/en/13/index.html
• 中文文档 https://www.osgeo.cn/sqlalchemy/index.html

Sometimes, if it’s not easy to add constriant condition on model.py in database level, we can try from application level by built-in methods pre_add https://flask-appbuilder.readthedocs.io/en/latest/api.html#flask_appbuilder.baseviews.BaseCRUDView.pre_add

security

Put sensitive data in file .env

SECRET_KEY=secret key

Use os module method getenv()

import os

secret_key = os.getenv("SECRET_KEY","default value")

issue

• Use JSON

• UNIQUE Index by UniqueConstraint https://stackoverflow.com/questions/10059345/sqlalchemy-unique-across-multiple-columns

• One issue in update row https://github.com/dpgaspar/Flask-AppBuilder/issues/1397

• has_key dict check key

• if there is error in log.info( error program ), console will not show that

• error example: finally is None

  def cut_string(s: str) -> str:
    begin = s.find(",")
    end = s.rfind(",")
    s = s[begin + 1:end]
  
    if len(s) > 255:
      cut_string(s)
    else:
      return s

• flake8 complains on boolean comparison “==” in filter clause sqlalchemy query condition is false