Flask hello.py 基本应用未运行？

Question

when I enter python hello.py in the command line, I get another bash prompt. I'm not sure what could be the problem since I'm able to run a virtualenv and when I check which version of flask I have the latest version, >>> '0.10.1' installed.

Opals-MacBook-Pro:~ opalkale$ cd myproject
Opals-MacBook-Pro:myproject opalkale$ ls
hello.py    venv
Opals-MacBook-Pro:myproject opalkale$ . venv/bin/activate
(venv)Opals-MacBook-Pro:myproject opalkale$ python hello.py
(venv)Opals-MacBook-Pro:myproject opalkale$ 

The code for hello.py looks like:

from flask import Flask
app = Flask(__name__)

@app.route("/")
def hello():
    return "Hello World!"

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

This code was taken from: http://flask.pocoo.org/docs/quickstart/#quickstart

Answer 1

Your file does not match the example in the documentation. You've placed the if __name__ == '__main__': block inside the definition of hello() .

Whitespace is significant in Python. It needs to be placed outside the function definition (ie, aligned all the way to the left). Doing so will execute the if when the script is run. The way it exists now, you would need to import the hello module and call the hello function. That isn't what you want. Fix the indentation and you will be all set.

Answer 2

If the server already works and when you back after a while you get this error: flask command not defined .

First run this command:

pip list

... if flask is not there reinstall it again.

1. Run this command:

# In mac
venv/bin/activate
# or Windows
venv/Scripts/activate

2. Install Flask running:

pip install Flask

3. Set environment variable

export FLASK_APP=yourServerName

4. Run flask back agan

flask run

Answer 3

Python always is a headache with these spaces. I use sublime text editor that helps me to figure out these spacing syntax issues really quick.

In your case, just move if name == " main ": to the left, so that that if is out of the function return above.

Hope that helps.

Answer 4

You must take care of Indentation . Tab and four blank spaces are different in it. Go with four blank spaces. You can re-create like below. I'm providing custom port also.

    from flask import Flask
    app = Flask(__name__)


    @app.route("/")
    def hello():
        return "Hello World!"


    if __name__ == "__main__":
        app.run(host='0.0.0.0', port=5000)