Python “ModuleNotFoundError：没有名为‘flask’的模块”

Question

I am a beginner with the python programming. I have python 3 installed in my local system. I coding along as part of a tutorial video and as part of the tutorial, i have created a virtual environment and created an app.py file with the below content.

from flask import Flask

app = Flask(__name__)

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

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

I have installed all the dependencies like flask and pytest in the virtual environment as per the tutorial using gitbash.But when i run the command python3 app.py in gitbash i get the below error message

 File "C:\path\Python\python-github-actions-example\src\app.py", line 1, in <module>
    from flask import Flask
ModuleNotFoundError: No module named 'flask'
(myvenv)

I checked the python version and it is python 3.9.7

If i run python app.py i get the output. Why is it not running even though correct version is installed

Any idea why?

Answer 1

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.

Answer 2

After you do what @krmogi says in their post above: https://stackoverflow.com/a/69623603/13855522

Start the app with python app.py not python3 app.py

Answer 3

Some times you need to change/select de versión/env if you after installed. like it if work for you.