gistfile1.py

from flask import Flask

app = Flask('__name__')

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

app.run()

# VS

(lambda flask:
    (lambda app:
        (app,
            app.route('/')(
                lambda: 'Hello World!'
            )
        )[0]
    )(flask.Flask('__name__')).run()
)(__import__('flask'))