Step-1: Creating & activating venv Windows:

  python -m venv venv
  ./venv/Scripts/activate

Linux:

  python -m venv venv
  source venv/bin/activate

Step-2: Installing Dependencies

  pip install -r requirements.txt

Step-3: Running application Windows:

  > $env:PYTHONDONTWRITEBYTECODE=1;$env:FLASK_APP="app";$env:FLASK_ENV = "development"
  > flask run

Linux:

  > export PYTHONDONTWRITEBYTECODE=1 FLASK_APP="app" FLASK_ENV="development"
  > flask run

  pip install -r requirements.txt

1. Creating pycache files Windows-powershell-Solution:

  $env:PYTHONDONTWRITEBYTECODE=1

Linux:

export PYTHONDONTWRITEBYTECODE=1

1. While activating venv this error occures in Windows:

       + CategoryInfo          : SecurityError: (:) [], PSSecurityException
       + FullyQualifiedErrorId : UnauthorizedAccess

   Solution: Execute this command and retry activating venv.

     Set-ExecutionPolicy -ExecutionPolicy RemoteSigned -Scope CurrentUser