Python Flask, Restarting with reloader: What does that mean [duplicate]

Question

I am trying to build y first webservice using Python Flask. I am not able to understand what does it mean for Flask to emit out Restarting with reloader, every time i run my app.

This is my code.

#!venv/bin/python
from flask import Flask
from flask import request


def buildCache():
    print 'Hello World'

buildCache()

app = Flask(__name__)


@app.route('/search')
def index():
    query = request.args.get('query','', type=str);
    return  query


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

when i run it

venv/bin/python ./app.py
Hello World
 * Running on http://127.0.0.1:5000/
 * Restarting with reloader
Hello World

I dont understand why buildCache method is being called twice? It seems to be related to "Restarting with the reoloader', what does that mean? How do i make sure that buildCache is only executed once, before the server starts.

Answer 1

This "reloads" the code whenever you make a change so that you don't have to manually restart the app to see changes. It is quite useful when you're making frequent changes.

You can turn off reloading by setting the debug parameter to False.

app.run(debug=False)

"[If debug=True] the debugger will kick in when an unhandled exception occurs and the integrated server will automatically reload the application if changes in the code are detected."

Source: http://flask.pocoo.org/docs/0.10/api/#flask.Flask.debug