Flask ImportError: No Module Named Flask

Question

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.

@MalikBrahimi When I run Python and then import flask and check what version I have installed, it gives back "0.10.1". So it looks like I have it installed... — anon_swe, Jul 06 '15 at 18:16
You're saying if you run python and then do `import flask` you have no errors? Is it possible you have to versions of python on your computer? — ari, Jul 06 '15 at 18:21
Can you insert `import sys; print sys.path` in that file (before the line where the error happens) and also run that in the interactive prompt? — ari, Jul 06 '15 at 18:25
@ari I tried to do the virtual environment thing but may have messed it up somehow? and yes, I'm using Python 3.3 but think I have 2.7 floating around — anon_swe, Jul 06 '15 at 18:50
You aren't using version 3, you are using version 2, and you have two copies of Python version 2 on your mac, one that came with OSX, and the other that you installed. So, all in all - it looks like you have three versions of Python; Python3, Python2 (you installed), Python2 (came with the system). Sounds like you aren't using the correct environment here; where you have installed Flask is not the system default, and this is likely the cause of your headache. — Burhan Khalid, Jul 06 '15 at 19:27
It is common nowadays to use conda - so the command would be 'conda install flask' — user1854182, Feb 17 '21 at 06:24
rare but possible: make sure your python file is not named 'flask.py' — user1854182, Feb 17 '21 at 06:25

score 165 · Accepted Answer · edited Oct 07 '20 at 05:12

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

You can place it anywhere as long as you run it with the virtualenv enabled. — Rollback, Oct 11 '17 at 13:16
Hi, I'm very new for python. Everything just works fine with virtualenv in terminal. But, my problem is I'm using IDE Atom... can atom run the code at the same virtualenv environment? — boog, Feb 13 '19 at 07:56

score 62 · Answer 2 · answered Nov 04 '17 at 19:18

62

For python 3 use

pip3 install flask

answered Nov 04 '17 at 19:18

Khalid Bin Huda

1,185
13
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4

After changing my python version from 2.7 to 3, it worked! – Ricardo Silva Nov 28 '17 at 22:16
Yes this works! Instead of doing pip install flask (which is for python 2), if you are using python3, you need to use pip3 install flask or other extensions of flask. To change your python version, you can use alias python="python3". – Lulu May 06 '19 at 02:52

score 12 · Answer 3 · answered Jun 01 '17 at 05:38

12

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.

answered Jun 01 '17 at 05:38

Julian

2,015
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or by doing this `export PYTHONPATH=/root/environments/my_env/lib/python3.6/site-packages/` – Carlos Oliveira Dec 16 '19 at 00:25

score 9 · Answer 4 · answered Jun 22 '17 at 04:40

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?

score 9 · Answer 5 · edited Dec 09 '18 at 07:40

9

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!

edited Dec 09 '18 at 07:40

rawplutonium

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answered Sep 24 '18 at 16:25

Bogdan001

91
1
1

Not sure why this is working, probably something to do with the path. Any insight on this? – nscalf Mar 22 '19 at 01:15

score 6 · Answer 6 · answered Oct 04 '18 at 13:09

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.

score 3 · Answer 7 · edited Aug 24 '17 at 08:21

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

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

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

score 3 · Answer 8 · answered Aug 16 '17 at 17:52

3

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.

answered Aug 16 '17 at 17:52

Norman Pilusa

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Ah its the simple things. I had the wrong libapache mod wsgi in my dockerfile after upgrading to python 3... have a +1 – Craicerjack Sep 21 '17 at 15:16

score 3 · Answer 9 · answered Jun 21 '18 at 20:20

3

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 :)

answered Jun 21 '18 at 20:20

Abid

250
6
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score 2 · Answer 10 · answered Aug 19 '20 at 23:31

2

Another thing - if you're using python3, make sure you are starting your server with python3 server.py, not python server.py

answered Aug 19 '20 at 23:31

Evan

1,156
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I upvoted this - such an common/easy mistake! – Brendan Metcalfe Jan 12 '21 at 20:52

score 1 · Answer 11 · edited Oct 16 '17 at 22:19

1

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).

edited Oct 16 '17 at 22:19

CDspace

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answered Oct 16 '17 at 21:08

Miguel

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yunus · Answer 12 · 2018-05-17T07:07:59.103

1

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.

edited May 17 '18 at 07:07

answered May 08 '18 at 12:00

yunus

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score 1 · Answer 13 · answered Apr 25 '19 at 11:56

This is what worked for me when I got a similar error in Windows; 1. Install virtualenv

pip install virtualenve

Create a virtualenv

virtualenv flask
Navigate to Scripts and activate the virtualenv

activate
Install Flask

python -m pip install flask
Check if flask is installed

python -m pip list

score 1 · Answer 14 · answered Jan 29 '21 at 10:08

The simplest answer to this problem is specifying the correct path to flask in your environment. Make sure the script you are running knows how to get to the flask installation. Using print(sys.path) as mentioned above certainly helped to figure out the path(s) the script was using.

score 0 · Answer 15 · answered Aug 21 '18 at 20:50

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.

score 0 · Answer 16 · answered May 01 '19 at 16:45

The flask script is nice to start a local development server, but you would have to restart it manually after each change to your code. That is not very nice and Flask can do better. If you enable debug support the server will reload itself on code changes, and it will also provide you with a helpful debugger if things go wrong. To enable debug mode you can export the FLASK_DEBUG environment variable before running the server: forexample your file is hello.py

$ export FLASK_APP=hello.py
$ export FLASK_DEBUG=1
$ flask run

Sonic Soul · Answer 17 · 2019-09-18T16:28:09.937

in my case using Docker, my .env file was not copied, so the following env vars were not set:

.env.local: FLASK_APP=src/app.py

so in my Dockerfile i had to include:

FROM deploy as dev
COPY env ./env

which was referenced in docker-compose.yml

env_file: ./env/.env.local

another thing i had to pay attention to is the path variable to ensure my environment is used

ENV PATH $CONDA_DIR/envs/:my_environment_name_from_yml_file:/bin:$CONDA_DIR/bin:$PATH```

score 0 · Answer 18 · answered Oct 03 '19 at 11:37

0

my answer just for any users that use Visual Studio Flesk Web project :

Just Right Click on "Python Environment" and Click to "Add Environment"

answered Oct 03 '19 at 11:37

hossein andarkhora

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score 0 · Answer 19 · answered Dec 29 '19 at 11:30

If you are using Pycharm then this is the virtual environment issue.

So, at the time of creating your Python project you will have to select "Existing interpreter" option -> click "system Interpreter" -> select the correct option for example "*\AppData\Local\Programs\Python\Python3.6\python.exe".

You can use 'New Virtual Env' as well, but I have just given the quick fix that should work for Pycharm users.

score 0 · Answer 20 · answered Mar 29 '21 at 19:13

I had a similar problem using WSL and PyCharm / VSCode, the problem only occurred in the development environment and not in production. I realized that IDE's with WSL can have problems when exporting PYTHONPATH from their work directory and I started to do it manually.

score -1 · Answer 21 · answered Nov 17 '18 at 13:36

-1

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

answered Nov 17 '18 at 13:36

ivanacorovic

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score -1 · Answer 22 · answered Mar 27 '21 at 07:28

Install Specific Version:

pip install flash

Upgrade flash

sudo pip3 install --upgrade flash

Getting Dependency Error in Window 10 Use code: easy_install instead of pip install

easy_install flash

Upgrade using easy install

sudo easy_install --upgrade  flash

On OSX System to install Module: Use code: brew install instead of pip install

brew install flash

Without Using Pip :

 sudo apt-get install -y flash

On CentOS7 or Linux Fedora:

yum -y install flash

Or on Fedora try

sudo dnf install flash

Command if Homebrew screws up your path on macOS:

python -m pip install flash

For Python3 MacOs Homebrew screws

python3 -m pip install flash

Verify module from list MacOs

pip freeze | grep  flash

For Execute on Anaconda as your python package manager

 conda install -c anaconda flash

Flask ImportError: No Module Named Flask

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