ModuleNotFoundError：没有名为“ flask”的模块-Ubuntu远程服务器

Question

I'm currently on Ubuntu 16.04 that I created through Digitalocean Droplet. I'm trying to run a simple flask application. I'm following this GUIDE However, I'm stuck on this step You can run the Flask app simply by running the following command: when I try running python app.py , I get the following...

Traceback (most recent call last):
  File "app.py", line 1, in <module>
    from flask import Flask
ModuleNotFoundError: No module named 'flask'
Error in sys.excepthook:
Traceback (most recent call last):
  File "/usr/lib/python3/dist-packages/apport_python_hook.py", line 63, in apport_excepthook
    from apport.fileutils import likely_packaged, get_recent_crashes
  File "/usr/lib/python3/dist-packages/apport/__init__.py", line 5, in <module>
    from apport.report import Report
  File "/usr/lib/python3/dist-packages/apport/report.py", line 30, in <module>
    import apport.fileutils
  File "/usr/lib/python3/dist-packages/apport/fileutils.py", line 23, in <module>
    from apport.packaging_impl import impl as packaging
  File "/usr/lib/python3/dist-packages/apport/packaging_impl.py", line 23, in <module>
    import apt
  File "/usr/lib/python3/dist-packages/apt/__init__.py", line 23, in <module>
    import apt_pkg
ModuleNotFoundError: No module named 'apt_pkg'

Original exception was:
Traceback (most recent call last):
  File "app.py", line 1, in <module>
    from flask import Flask
ModuleNotFoundError: No module named 'flask'

Also, flask is already installed.

Requirement already satisfied: flask in /usr/local/lib/python3.5/dist-packages (1.0.2)
Requirement already satisfied: Werkzeug>=0.14 in /usr/local/lib/python3.5/dist-packages (from flask) (0.14.1)
Requirement already satisfied: itsdangerous>=0.24 in /usr/local/lib/python3.5/dist-packages (from flask) (0.24)
Requirement already satisfied: Jinja2>=2.10 in /usr/local/lib/python3.5/dist-packages (from flask) (2.10)
Requirement already satisfied: click>=5.1 in /usr/local/lib/python3.5/dist-packages (from flask) (6.7)
Requirement already satisfied: MarkupSafe>=0.23 in /usr/lib/python3/dist-packages (from Jinja2>=2.10->flask) (0.23)

While the environment is active, I get the below stack trace when I run python app.py

Traceback (most recent call last):
  File "app.py", line 10, in <module>
    app.run(debug=True)
  File "/home/.env/lib/python3.5/site-packages/flask/app.py", line 910, in run
    cli.load_dotenv()
  File "/home/.env/lib/python3.5/site-packages/flask/cli.py", line 608, in load_dotenv
    dotenv.load_dotenv(path)
  File "/home/.env/lib/python3.5/site-packages/dotenv/main.py", line 255, in load_dotenv
    return DotEnv(f, verbose=verbose).set_as_environment_variables(override=override)
  File "/home/.env/lib/python3.5/site-packages/dotenv/main.py", line 95, in set_as_environment_variables
    for k, v in self.dict().items():
  File "/home/.env/lib/python3.5/site-packages/dotenv/main.py", line 74, in dict
    values = OrderedDict(self.parse())
  File "/home/.env/lib/python3.5/site-packages/dotenv/main.py", line 79, in parse
    f = self._get_stream()
  File "/home/.env/lib/python3.5/site-packages/dotenv/main.py", line 62, in _get_stream
    return io.open(self.dotenv_path)
IsADirectoryError: [Errno 21] Is a directory: '/home/.env'

Answer 1

@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, eg

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, ie, 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.