Flask Installed, But Modulenotfounderror: No Module Named 'Flask'

Flask ImportError: No Module Named Flask

Try deleting the virtualenv you created. Then create a new virtualenv with:

virtualenv flask

Then:

cd flask

Now let's activate the virtualenv

source bin/activate

Now you should see (flask) on the left of the command line.

_{Edit: In windows there is no "source" that's a linux thing, instead execute the activate.bat file, here I do it using Powershell: PS C:\DEV\aProject> & .\Flask\Scripts\activate)}

Let's install flask:

pip install flask

Then create a file named hello.py (NOTE: see UPDATE Flask 1.0.2 below):

from flask import Flask
app = Flask(__name__)

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

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

and run it with:

python hello.py

UPDATE Flask 1.0.2

With the new flask release there is no need to run the app from your script. hello.py should look like this now:

from flask import Flask
app = Flask(__name__)

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

and run it with:

FLASK_APP=hello.py flask run

Make sure to be inside the folder where hello.py is when running the latest command.

All the steps before the creation of the hello.py apply for this case as well

Python ModuleNotFoundError: No module named 'flask'

Try to delete the venv or make a new one.

1. Then create a new venv like this:
   virtualenv flask

2. Go to the flask directory
   : cd flask

3. Activate it: scripts\activate

   • You should see (flask) on the left of the command line.

4. Install flask again: pip install flask

5. Run your file again.

ModuleNotFoundError: No module named 'flask'

pip can for some reason point to system-wide pip (which on many systems corresponds to Python 2.7). In order to use pip from the virtualenv, use python -m pip command. The following command will do the trick:

pip uninstall flask && python -m pip install flask

Another possibility is that you installed flask via apt and not pip. Here's the difference between the two: What is the difference between `sudo apt install python3-flask` and `pip3 install Flask`?

So now the flask command is available system-wide.

If this is the case, uninstalling flask with apt and installing it with pip should do the trick:

sudo apt remove python-flask
pip install flask

(this is my guess that the apt package is called python-flask.

ModuleNotFoundError: No module named 'flask' - Ubuntu Remote Server

@Abhilash looks like the problem isn't the code, it's about the setup.

By default, Python will look for flask environment configurations in the home directory, which generally is stored in the .env file. In your case that is the virtual environment. Hence the error.

Follow the steps below:

Go to your user's document directory, e.g.

cd /home/rahul/Documents/

Create a separate folder for your flask application:

mkdir flask_test_app

Go into the above directory:

cd flask_test_app

Create Virtual Environment here:

virtualenv .env

Activate this virtual environment:

source .env/bin/activate

It should show the something like below:

(.env) rahul@ramco:~/Documents/flask_test_app

Install Flask:

pip install Flask

Put the flask app file created in the current folder, i.e., app.py file.

Run the application:

python app.py

This will start the flask app on flask's default port 5000, and will display something like below in the terminal:

 * Tip: There are .env files present. Do "pip install python-dotenv" to use them.
 * Serving Flask app "app" (lazy loading)
 * Environment: production
   WARNING: Do not use the development server in a production environment.
   Use a production WSGI server instead.
 * Debug mode: on
 * Running on http://127.0.0.1:5000/ (Press CTRL+C to quit)
 * Restarting with stat
 * Tip: There are .env files present. Do "pip install python-dotenv" to use them.
 * Debugger is active!
 * Debugger PIN: 303-406-109

NOTE: Try to avoid creating a virtual environment in the home directory, if you have to then use some other name like .venv or venv. So that it won't conflict with the default configurations.

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