Flask ImportError: No Module Named Flask

问题:

I'm following the Flask tutorial here:

http://blog.miguelgrinberg.com/post/the-flask-mega-tutorial-part-i-hello-world

I get to the point where I try ./run.py and I get:

Traceback (most recent call last):
  File "./run.py", line 3, in <module>
    from app import app
  File "/Users/benjaminclayman/Desktop/microblog/app/__init__.py", line 1, in <module>
    from flask import Flask
ImportError: No module named flask

This looks similar to:

ImportError: No module named flask

But their solutions aren't helpful. For reference, I do have a folder named flask which one user mentioned may cause issues.

回答1:

try deleting the virtualenv you created. create a new virtualenv

virtualenv flask

then

cd flask

let's activate the virtualenv

source bin/activate

now you should see (flask) on the left of the command line. Let's install flask

pip install flask

Then create a file hello.py

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

回答2:

For python 3 use

pip3 install flask

回答3:

The only way I could solve was by adding my users python dir to myapp.wsgi file. As an example:

sys.path.append('/home/deployer/anaconda3/lib/python3.5/site-packages')

I guess that if you install the packages in the global enviroment, you should have no problem, but I had my python packages installed as user.

回答4:

I had a similar problem with flasgger.

The reason for that was that I always use

sudo pip install flask

but for some reason that's not always the way to go. Sometimes, you have to do just

pip install flask

Another gotcha is that sometimes people type pip install Flask with the cap F

Posting this here in case somebody gets stuck. Let me know if it helped.

Useful Link: What is the difference between pip install and sudo pip install?

回答5:

I was using python2 but installed this: sudo apt-get install libapache2-mod-wsgi-py3

Instead of: sudo apt-get install libapache2-mod-wsgi

Correcting the installation solved the no flask problem.

回答6:

1. Edit /etc/apache2/sites-available/FlaskApp.conf
2. Add the following two lines before the "WSGIScriptAlias" line:

WSGIDaemonProcess FlaskApp python-home=/var/www/FlaskApp/FlaskApp/venv/FlaskApp WSGIProcessGroup FlaskApp

3. Restart Apache:service apache2 restart

I'm following the Flask tutorial too.And I met the same problem.I found this way to fix it.

http://blog.miguelgrinberg.com/post/the-flask-mega-tutorial-part-i-hello-world

回答7:

Go to the flask file in microblog, then activate the virtual environment with source bin/activate, then go to flask/bin and install flask, and the rest of the packages, pip install flask. You will see flask listed inside bin directory. Try to run ./run.py again from microblog (or from wherever you have the file).

回答8:

In my case the solution was as simple as starting up my virtual environment like so:

$ venv/scripts/activate

It turns out I am still fresh to Python :)

回答9:

this is what worked for me,

sudo -H pip install flask

Or for pip3(python3) use :

sudo -H pip3 install flask

Sidenote

If you're using virtualenv it's a good idea to pip freeze >> requirements.txt to allow for the installed packages to be listed in one place. The sudo command and -H flag. For more on sudo's -H flag, look at Paul's answer. Hope this helps you.

回答10:

After activating the virtual environment and installing Flask, I created an app.py file. I run it like this : python -m flask run. Hope this will help!

回答11:

Even i too suggest u virtualenv, This might also solve ur problem.

sudo apt install python-flask

If u want to deploy in productionserver then go ahead with above solution else use virtualenv.

回答12:

enter your python interactive mode then:

import sys

sys.path

it will print your path. Check wether flask is installed in the sys.path.

For MacOS, python path is under /opt/local/Library/Frameworks/Python.framework/Versions/2.7/lib/python2.7/site-packages

But pip'll install python package by default under /Library/Python/2.7/site-packages

That's why it doesn't work for MacOS.

回答13:

It worked for me after upgrading pip:

curl https://bootstrap.pypa.io/get-pip.py | python

Found that answer here: https://stackoverflow.com/a/49748494/3197202

Then I could just install flask:

pip install flask