Env. Variables not set while running Minimal Flask application

Your code is correct. Try setting the Command-Line variable like this :

setx FLASK_APP run.py

And then run it : flask run.

I fixed the same problem by closing the command window and restart it.

You have to set the FLASK_APP variable outside of the virtual environment. I’m assuming the reason that it worked after @Fang restarted the command window is because that action automatically exited the virtual environment.

So, if you’re in the virtual environment (indicated by a (venv) at the start of line on command window), then type the following commands:

deactivate

set FLASK_APP=run.py

venvscriptsactivate

flask run

Did you run your terminal as administrator? I had the same problem, and running cmd/PowerShell as admin fixed it for me.

Edit: I spoke too soon. Running as admin did nothing.

The real answer (to my problem, at least) is a combination of some of the other answers.

1. Instead of using set FLASK_APP = myApp.py, use setx FLASK_APP myApp.py
2. Restart the terminal, and FLASK_APP will have the new value

1. export FLASK_APP=run.py
2. flask run --host=0.0.0.0

then can run normally, output something like:

 * Serving Flask app "hello"
 * Forcing debug mode on
 * Running on http://0.0.0.0:5000/ (Press CTRL+C to quit)
 * Restarting with stat
 * Debugger is active!
 * Debugger pin code: 353-795-063

Success with setx FLASK_APP test.py . Note: if not run, close command line and start other one.

D:projectsflask-oauthlibpy2>.evnScriptsactivate

(.evn) D:projectsflask-oauthlibpy2>setx FLASK_APP test.py

SUCCESS: Specified value was saved.

(.evn) D:projectsflask-oauthlibpy2>flask run
 * Serving Flask app "flask-oauthlibpy2.test"
 * Running on http://127.0.0.1:5000/ (Press CTRL+C to quit)
127.0.0.1 - - [24/May/2017 14:35:06] "GET / HTTP/1.1" 200 -

Just drop the space around ‘=’ !

After half an hour searching for solution, I finally get what does ‘You did not provide the FLASK_APP environment variable’ mean. Because what I set is ‘FLASK_APP ‘ variable (with space).

had a similar problem. got resolved by using the following:
flask run –no-reload

learnt this from flask documentation http://flask.pocoo.org/docs/0.12/server/

If you are using powershell it does not works i dont know why
please use cmd.exe
since i use VScode editor it provide powershell as a terminal(ctrl + back-tick) by default so i was trying to run flask app on the powershell and it was giving me same response as you are getting

1. open cmd.exe (or if you are VSCode user like me simply write cmd on that terminal, or you can also press Ctrl + Shift + C to open a windowed cmd terminal)

2. set FLASK_APP=hello.py (without spaces, only for first run then it remember until restart of cmd)

3. flask run (or just flask will also work)

note: this is only for windows user

I had got the same issue while running the first hello world for flask.

Ideally there should not be any space between
so use
set FLASK_APP=run.py

I was having this same problem running the commands as stated in Flask quick start. using Powershell on windows 10

projects>set export FLASK_APP=hello.py
projects>flask run
 * Running on http://127.0.0.1:5000/

I needed to type python <filename.py> while being in the directory containing the file with
from flask import Flask
app = Flask(name)

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

after that you will get a message with an IP address in it

 * Running on http://127.0.0.1:5000/ (Press CTRL+C to quit)

you copy IP address into your browser and your to that point you should see your hello world statement then.

I wonder why this is missing from the answer.

Here is a simple solution:

add app.run(port=5000)

from flask import Flask
app = Flask(__name__)

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

app.run(port=5000)

and then in the same directory run the command

python run.app

Just drop the space around equal to sign.
set FLASK_APP=python_file_name.py

I was having the same problem, but the following command worked for me in PowerShell:

python -m flask run

I had the same issue on windows and found a solution from the flask documentation: https://flask.palletsprojects.com/en/1.1.x/tutorial/factory/

My file structure:
Flask_folder>>app

(NB! app folder contains: __init_.py and routes.py)

> set FLASK_APP=app

> set FLASK_ENV=development

> flask run

Here is what worked for me:

• Step 1: Open your CMD Command prompt
• Step 2: Go on the same directory in which my python file was on.
• Step 3: in the CMD command prompt run the command setx FLASK_APP sqlAlchemy.py
• Step 4: close terminal
• Step 5: In the CMD command prompt run the command python - m flask run

I have an Alienware laptop and am using Windows 10.

Not sure it worked but it was a combination of trial and ever.
Depending on the OS you have the solution will vary it seems.
IT could be an environmental variable issue but again not sure.

–
Here are other possible solutions that didn’t work for me but I gathered them up as possibilities.

• OPTION 2
• set FLASK_APP=sqlalchemy.py
  • flask run
• OPTION 3
• set FLASK_APP=app
• set FLASK_ENV=development
  • flask run
    Hope this helps.

Different shell programs have different ways to set the environment variable in it. So that Flask can discover you application correctly.

• Unix Bash/Zsh (Linux, Mac, etc.):

  $ export FLASK_APP=hello
  $ flask run
  

• Windows CMD:

  > set FLASK_APP=hello
  > flask run
  

• Windows PowerShell:

  > $env:FLASK_APP = "hello"
  > flask run
  

You can find more infomation in the Flask docs.

    > set FLASK_APP=Your_file_name.py
    > set FLASK_ENV=development
    > flask run

it must be work for windows user only

You should leave a space between the equal sign and the file name like this in PowerShell in Windows.

set FLASK_APP= market.py

this worked for me.