when I translate the book, if I find some typo or syntax error, it's hard to pull requests, so I open the issue.

http://www.fullstackpython.com/flask.html

this page, the example code of flask's hello world application has a syntax error, it should be like below:

from flask import Flask
app = Flask(__name__)

@app.route('/')
def hello_world():
    return 'Hello World!'

if __name__ == '__main__':
    app.run()

By the way, I have translate 2 pages(click this)into Chinese, and I have read half of the book, write excellently which provide rich resources and the checklists is very particle, I learned much from the book.