Xtykutl

I try to setup a website based on Flask on a Raspberry Pi 3B+, with Apache2 (2.4.25), and mod_wsgi, but I am unable to import the module flask_cors in Python3.5...

I installed mod_wsgi with the command ssudo apt-get install libapache2-mod-wsgi

Because I only plan on using the Raspberry for hosting my website, I tried to install the packages needed by Flask system-wide, with the version 3.5 of Python, with the following command: pip3 install -r requirements.txt where requirements.txt is the following:

click==6.7

Flask==0.12.3

Flask-Cors==3.0.3

itsdangerous==0.24

Jinja2==2.9.6

MarkupSafe==1.0

six==1.11.0

Werkzeug==0.12.2

Requests==2.20.0

I think I understood that on a Raspi, it is best to import the modules wit the command pip3 install -U <module> because the packages are not installed on the default location for python, which is confirmed in my case by the following command python -m site that yields the following information:

sys.path = [

    '/home/pi/.local/lib/python3.5/site-packages',

    '/usr/lib/python35.zip',

    '/usr/lib/python3.5',

    '/usr/lib/python3.5/plat-arm-linux-gnueabihf',

    '/usr/lib/python3.5/lib-dynload',

    '/usr/local/lib/python3.5/dist-packages',

    '/usr/local/lib/python3.5/dist-packages/virtualenv-16.1.0-py3.5.egg',

    '/usr/lib/python3/dist-packages',

]

USER_BASE: '/home/pi/.local' (exists)

USER_SITE: '/home/pi/.local/lib/python3.5/site-packages' (exists)

ENABLE_USER_SITE: True

My Flask and dependencies are indeed installed in the /home/pi/.local/lib/python3.5/site-packages folder. But this does not seem to be a problem because when checking for importing on a python shell, everything seems fine systemwide:

pi@raspberrypi:~ $ python3

Python 3.5.3 (default, Sep 27 2018, 17:25:39) 

[GCC 6.3.0 20170516] on linux

Type "help", "copyright", "credits" or "license" for more information.

>>> from flask_cors import CORS

>>> 

Knowing that, I tried to put the following files to setup my apache server:

flaskregul.conf in the folder /etc/apache2/sites-enabled:

<VirtualHost *:80>

    WSGIScriptAlias / /var/www/flaskregul/flaskregul.wsgi

    Alias /static/ /var/www/flaskregul/dist/static/

    <Directory /var/www/flaskregul/dist/static>

        WSGIProcessGroup flaskregul

            WSGIApplicationGroup %{GLOBAL}

        Order allow,deny

        Allow from all

    </Directory>

    ErrorLog /var/log/apache2/flask.monnomdedomaine.com.log

    LogLevel warn

    CustomLog ${APACHE_LOG_DIR}/access.log combined

</VirtualHost>

flaskregul.wsgi in /var/www/flaskregul:

import sys

sys.path.insert(0,"/var/www/flaskregul") # path to my __init__.py file

sys.path.insert(0,"/home/pi/.local/lib/python3.5/site-packages") # path to the site-packages folder where the modules are installed by pip3

from __init__ import app as application

__init__.py in /var/www/flaskregul:

from flask import Flask

from flask_cors import CORS

I encounter an impossibilty to specifically import the flask_cors module, because the launching of the file __init__.py yields the following errors in the file /var/log/apache2/flask.monnomdedomaine.com.log:

[Sat Nov 10 00:37:22.220394 2018] [wsgi:error] [pid 6804:tid 1955591216] [client 192.168.1.67:33550] mod_wsgi (pid=6804): Target WSGI script '/var/www/flaskregul/flaskregul.wsgi' cannot be loaded as Python module.

[Sat Nov 10 00:37:22.220972 2018] [wsgi:error] [pid 6804:tid 1955591216] [client 192.168.1.67:33550] mod_wsgi (pid=6804): Exception occurred processing WSGI script '/var/www/flaskregul/flaskregul.wsgi'.

[Sat Nov 10 00:37:22.221936 2018] [wsgi:error] [pid 6804:tid 1955591216] [client 192.168.1.67:33550] Traceback (most recent call last):

[Sat Nov 10 00:37:22.222365 2018] [wsgi:error] [pid 6804:tid 1955591216] [client 192.168.1.67:33550]   File "/var/www/flaskregul/flaskregul.wsgi", line 1, in <module>

[Sat Nov 10 00:37:22.222395 2018] [wsgi:error] [pid 6804:tid 1955591216] [client 192.168.1.67:33550]     from __init__ import app as application

[Sat Nov 10 00:37:22.222445 2018] [wsgi:error] [pid 6804:tid 1955591216] [client 192.168.1.67:33550]   File "/var/www/flaskregul/__init__.py", line 2, in <module>

[Sat Nov 10 00:37:22.222463 2018] [wsgi:error] [pid 6804:tid 1955591216] [client 192.168.1.67:33550]     from flask_cors import CORS

[Sat Nov 10 00:37:22.222557 2018] [wsgi:error] [pid 6804:tid 1955591216] [client 192.168.1.67:33550] ImportError: No module named 'flask_cors'

Whereas the import of Flask seems fine...

I've tried to debug this by changing the WSGI script file by this one:

import sys

sys.path.insert(0,"/var/www/flaskregul")

sys.path.insert(0,"/home/pi/.local/lib/python3.5/site-packages")



def application(environ, start_response):

    status = '200 OK'



    output = u''

    output += u'sys.version = %sn' % repr(sys.version)

    output += u'sys.prefix = %sn' % repr(sys.prefix)

    output += u'sys.path = %sn' % repr(sys.path)



    response_headers = [('Content-type', 'text/plain'),

                        ('Content-Length', str(len(output)))]

    start_response(status, response_headers)



    return [output.encode('UTF-8')] 

This is a piece of advice the advice on this web page from mod_wsgi: https://modwsgi.readthedocs.io/en/develop/user-guides/checking-your-installation.html. When opening the webpage, I obtain this result:

sys.version = '3.5.3 (default, Sep 27 2018, 17:25:39) n[GCC 6.3.0 20170516]'

sys.prefix = '/usr'

sys.path = ['/home/pi/.local/lib/python3.5/site-packages', '/var/www/flaskregul', '/usr/lib/python35.zip', '/usr/lib/python3.5', '/usr/lib/python3.5/plat-arm-linux-gnueabihf', '/usr/lib/python3.5/lib-dynload', '/usr/local/lib/python3.5/dist-packages', '/usr/local/lib/python3.5/dist-packages/virtualenv-16.1.0-py3.5.egg', '/usr/lib/python3/dist-packages']

I have the impression that the path is correct! I actually succeed in importing my own modules located in the /var/www/flaskregul location...

I am lost, I don't understand why specifically the module flask_cors is unavaiblable, because it is indeed in the path:

pi@raspberrypi:~/.local/lib/python3.5/site-packages $ l | grep flask

drwxr-xr-x 5 pi pi   4096 nov.   9 23:30 flask

drwxr-xr-x 3 pi pi   4096 nov.  10 00:08 flask_cors

pi@raspberrypi:~/.local/lib/python3.5/site-packages $ l flask_cors 

total 44

-rw-r--r-- 1 pi pi 13771 nov.  10 00:08 core.py

-rw-r--r-- 1 pi pi  4937 nov.  10 00:08 decorator.py

-rw-r--r-- 1 pi pi  7405 nov.  10 00:08 extension.py

-rw-r--r-- 1 pi pi   924 nov.  10 00:08 __init__.py

drwxr-xr-x 2 pi pi  4096 nov.  10 00:08 __pycache__

-rw-r--r-- 1 pi pi    22 nov.  10 00:08 version.py

Any help would be very much appreciated! I am currently losing my hair at a worriyng rate!

Oh my god I solved it in a desperate try before giving up.

I executed the following commands on a shell: (pip is the pip of the python3.5 /!)

pip uninstall flask

pip uninstall flask_cors

sudo pip install --upgrade pip

hash -d pip

sudo pip install -U flask

sudo pip install -U flask_cors

Website up and running! :D