Why does localhost:5000 not work in Flask Python?

Question

I'm using flask app factory pattern like and have this helloworld.py file

from flask import Flask

app = Flask(__name__)


@app.route('/')
def index():
    return 'This is the home page'


if __name__=="__name__":
    app.run(debug=True)

Then I run the app in Terminal :

python helloworld.py

(venv) C:\Users\Jayalakshmi.S1\myproject>python helloworld.py

(venv) C:\Users\Jayalakshmi.S1\myproject>

But when I go to http://localhost:5000 it doesn't work. It says:

Can’t reach this page

Make sure the web address http://127.0.0.1:5000 is correct

What could be wrong?

abarnert · Accepted Answer · 2018-05-11 06:44:15Z

4

The problem is that you wrote if __name__=="__name__": instead of if __name__=="__main__":.

Since that will never be true, your app.run never happens. That's why when you run the script, it just returns immediately, instead of printing out something like * Running on http://127.0.0.1:5000/ and then waiting.

You also almost always want to run Flask this way:

set FLASK_APP=helloworld.py
flask run

… instead of:

python helloworld.py

edited May 11, 2018 at 6:44

answered May 11, 2018 at 6:42

abarnert

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4 Comments

Jayalakshmi Over a year ago

Thank you...Thank you so much

Cleb Over a year ago

Shouldn't this be export instead of set?!

abarnert Over a year ago

@Cleb On Windows?

abarnert Over a year ago

@Cleb Well, that's actually bash, not Unix… but close enough; most people on Unix systems (with a terminal) are either using bash, or know what they're doing (and anyone using bash on Windows knows what they're doing). But anyway, the OP is clearly on Windows, given the C:\Users\Jayalakshmi.S1\myproject>, so it shouldn't be export.

Raja Simon · Accepted Answer · 2018-05-11 06:42:48Z

1

Your if condition is wrong. You should mention the main module which you're running...

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

answered May 11, 2018 at 6:42

Raja Simon

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