nameerror 3a name 27name 27 is not defined flask

1from flask import Flask
2app = Flask(_name_)
3
4@app.route("/")
5def hello():
6    return "hello world!"
7    app.run()
8    
9
10    

1from flask import Flask
2app = Flask(__name__) # underscore should be two times before and after name
3
4@app.route("/")
5def hello():
6    return "hello world!"
7    app.run()