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• What is python-dev package?
  • python-dev is a package that contain Python C API. It is used because of its high performance.
  • The discussion about this matter is here, http://stackoverflow.com/questions/31002091/what-is-python-dev-package-used-for.
• There is a Python virtual environment wrapper, however I would not install it and keep using the method that is from Flask website.
• All in all I prefer to make Python virtual environment with the method from Flask guide for this moment. And I would not use the method from this book until I got clear understanding on what is the benefit of each others.
• There is this touch command that is native to Linux. It is used to create an empty file. This is pretty neat to make a blank .md file or blank .py file.
• What is the usage coding:utf-8 in the beginning of the Flask entry file?
  • To tell Python which encoding used for this application.
  • Also to prevent from nasty bug (?).
• What is __name__ means in Python programming?
  • I think it used to determine the root of the project.
  • In case the __name__ is not __main__ then the executed codes might comes from other packages.
  • Check here, http://stackoverflow.com/questions/419163/what-does-if-name-main-do.

if __name__ == "__main__":
    app.run(

• If you want to test your Flask project try to use these commands.

export FLASK_APP=your_entry_file.py
flask run

• Or you can just run Flask application using python your_entry_file.py without even export FLASK_APP=your_entry_file.py. I am not sure what are the differences.
• What happened if you change to other Python virtual environment without using deactivate first?
  • If you want to refactor your project you need to make new virtual environment delete the venv folder and initiate virtualenv venv again.
  • Because, otherwise the path is still tact into the old directory.