Flask can't see modules installed by pip

Question

I installed Flask on Python 2.7.12/Apache 2.4/Ubuntu 16.04.1 LTS. I've been using these two tutorials to get set up. I'm not running venv or any other virtual environment (unlike this post). Running a simple Flask app works fine (a la "hello world"). I have a flaskapp.wsgi and a flaskapp.py in the same directory (/var/www/html).

flaskapp.wsgi

import sys
sys.path.insert(0, "/var/www/html/flaskapp")
from flaskapp import app as application

flaskapp.py

from flask import Flask
app = Flask(__name__)

@app.route('/')
def main():
    return "hello world"

if __name__ == '__main__':
    app.run()

But when I try to import a module outside of the basic set of Flask modules, eg. httplib2 (which I installed via pip), I get a 500 HTTP error. Simply adding import httplib2 to flaskapp.py throws this error.

Looking at the Apache error logs I see the following:

[wsgi:error] mod_wsgi (pid=22739): Target WSGI script '/var/www/html/flaskapp/flaskapp.wsgi' cannot be loaded as Python module.
[wsgi:error] mod_wsgi (pid=22739): Exception occurred processing WSGI script '/var/www/html/flaskapp/flaskapp.wsgi'.
[wsgi:error] Traceback (most recent call last):
[wsgi:error] File "/var/www/html/flaskapp/flaskapp.wsgi", line 7, in <module>
[wsgi:error] from flaskapp import app as application
[wsgi:error] File "/var/www/html/flaskapp/flaskapp.py", line 7, in <module>
[wsgi:error] import httplib2
[wsgi:error] ImportError: No module named httplib2

When I run python (not using Flask), I can import httplib2 without trouble. So it seems for some reason my Flask app can't access pip's imports.

Here's what I've done to troubleshoot so far:

I checked to see where httplib2 lives, using __file__:

>>> import httplib2
>>> httplib2.__file__
'/home/andrew/.local/lib/python2.7/site-packages/httplib2/__init__.pyc'

Then I checked both sys.path and pip.get_installed_distributions() from within the Flask app:

flaskapp.py (revised)

from flask import Flask, jsonify
import pip, sys

modules = ""
for i in pip.get_installed_distributions():
    modules = modules + " " + str(i)

app = Flask(__name__)

@app.route('/')
def main():
    return jsonify({ "modules":modules, "sys.path":sys.path })

if __name__ == '__main__':
    app.run()

output:

{
  "available_modules": " Flask 0.12 Jinja2 2.9.5 itsdangerous 0.24 Werkzeug 0.11.15 MarkupSafe 0.23 click 6.7", 
  "sys.path": [
    "/usr/share/python-wheels/lockfile-0.12.2-py2.py3-none-any.whl", 
    "/usr/share/python-wheels/pkg_resources-0.0.0-py2.py3-none-any.whl", 
    "/usr/share/python-wheels/retrying-1.3.3-py2.py3-none-any.whl", 
    "/usr/share/python-wheels/requests-2.9.1-py2.py3-none-any.whl", 
    "/usr/share/python-wheels/wheel-0.29.0-py2.py3-none-any.whl", 
    "/usr/share/python-wheels/urllib3-1.13.1-py2.py3-none-any.whl", 
    "/usr/share/python-wheels/ipaddress-0.0.0-py2.py3-none-any.whl", 
    "/usr/share/python-wheels/colorama-0.3.7-py2.py3-none-any.whl", 
    "/usr/share/python-wheels/distlib-0.2.2-py2.py3-none-any.whl", 
    "/usr/share/python-wheels/pyparsing-2.0.3-py2.py3-none-any.whl", 
    "/usr/share/python-wheels/packaging-16.6-py2.py3-none-any.whl", 
    "/usr/share/python-wheels/html5lib-0.999-py2.py3-none-any.whl", 
    "/usr/share/python-wheels/CacheControl-0.11.5-py2.py3-none-any.whl", 
    "/usr/share/python-wheels/six-1.10.0-py2.py3-none-any.whl", 
    "/usr/share/python-wheels/chardet-2.3.0-py2.py3-none-any.whl", 
    "/usr/share/python-wheels/progress-1.2-py2.py3-none-any.whl", 
    "/usr/share/python-wheels/setuptools-20.7.0-py2.py3-none-any.whl", 
    "/usr/share/python-wheels/pip-8.1.1-py2.py3-none-any.whl", 
    "/var/www/html/flaskapp", 
    "/usr/lib/python2.7", 
    "/usr/lib/python2.7/plat-x86_64-linux-gnu", 
    "/usr/lib/python2.7/lib-tk", 
    "/usr/lib/python2.7/lib-old", 
    "/usr/lib/python2.7/lib-dynload", 
    "/usr/local/lib/python2.7/dist-packages", 
    "/usr/lib/python2.7/dist-packages"
  ]
}

So it can see the path where httplib2 lives, as well as the path to flask, but the available modules are only the Flask modules.

I'm not sure if this is a problem with my Apache configuration - I've consulted a number of how-tos and documentation, and this is the setup I've been using:

/etc/apache2/sites-enabled/000-default.conf

<VirtualHost *:80>

    WSGIDaemonProcess flaskapp threads=5 python-path=/var/www/html/flaskapp/flaskapp
    WSGIScriptAlias / /var/www/html/flaskapp/flaskapp.wsgi

    ErrorLog ${APACHE_LOG_DIR}/error.log
    CustomLog ${APACHE_LOG_DIR}/access.log combined

    <Directory  /var/www/html/flaskapp>
       WSGIProcessGroup flaskapp
       WSGIApplicationGroup %{GLOBAL}
       Require all granted
       WSGIScriptReloading On
    </Directory>

</VirtualHost>  

I've looked through a number of SO posts, but most seem concerned with app not being visible to WSGI. Some posts seem close, but haven't solved my problem. I'd really appreciate any advice!

Note: I'm pretty comfortable with Python, familiar-ish with Flask, but pretty novice with Apache and WSGI. Detailed explanations/links for answers concerning the latter two topics (if appropriate) would really help.

Answer 1

You should add ~/.local/ to python-path on your Apache configuration.

WSGIDaemonProcess flaskapp threads=5 python-path=/var/www/html/flaskapp/flaskapp:/home/andrew/.local

You should also try to use virtual environments, and set python-home on WSGIDaemonProcess as the environment root.

Source: http://modwsgi.readthedocs.io/en/develop/configuration-directives/WSGIDaemonProcess.html

EDIT

You can also install httplib2 with sudo just like you installed the flask packages (as seen in one of your links)