I get 'ImportError: No module named web' despite the fact that it is installed

I would like to run a simple 'Hello world' app. Every time I run it I get

'ImportError: No module named web'

I installed web.py using pip and using easy_install several times. I tried uninstalling it and installing again. I tried installing it a as sudo. Nothing seems to work. I use OS X

Code of the application:

import web

urls = (
  '/', 'index'
)

app = web.application(urls, globals())

class index:
    def GET(self):
        greeting = "Hello World"
        return greeting

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

I tried to run this app using this commend:

python /Users/mptorz/webversion/bin/app.py http://0.0.0.0:8080/

However I know that this is not an issue of the code, because I am basically doing this course http://learnpythonthehardway.org/book/ex50.html.

I thought it might be interesting. I have just tried again to reinstall web.py and I have got this error:

pc7:~ mptorz$ pip uninstall web.py
Uninstalling web.py-0.40.dev0:
  /usr/local/lib/python2.7/site-packages/web.py-0.40.dev0-py2.7.egg
Proceed (y/n)? y
Exception:
Traceback (most recent call last):
  File "/usr/local/lib/python2.7/site-packages/pip/basecommand.py", line 215, in main
    status = self.run(options, args)
  File "/usr/local/lib/python2.7/site-packages/pip/commands/uninstall.py", line 76, in run
    requirement_set.uninstall(auto_confirm=options.yes)
  File "/usr/local/lib/python2.7/site-packages/pip/req/req_set.py", line 336, in uninstall
    req.uninstall(auto_confirm=auto_confirm)
  File "/usr/local/lib/python2.7/site-packages/pip/req/req_install.py", line 742, in uninstall
    paths_to_remove.remove(auto_confirm)
  File "/usr/local/lib/python2.7/site-packages/pip/req/req_uninstall.py", line 115, in remove
    renames(path, new_path)
  File "/usr/local/lib/python2.7/site-packages/pip/utils/__init__.py", line 267, in renames
    shutil.move(old, new)
  File "/usr/local/Cellar/python/2.7.12/Frameworks/Python.framework/Versions/2.7/lib/python2.7/shutil.py", line 300, in move
    rmtree(src)
  File "/usr/local/Cellar/python/2.7.12/Frameworks/Python.framework/Versions/2.7/lib/python2.7/shutil.py", line 247, in rmtree
    rmtree(fullname, ignore_errors, onerror)
  File "/usr/local/Cellar/python/2.7.12/Frameworks/Python.framework/Versions/2.7/lib/python2.7/shutil.py", line 252, in rmtree
    onerror(os.remove, fullname, sys.exc_info())
  File "/usr/local/Cellar/python/2.7.12/Frameworks/Python.framework/Versions/2.7/lib/python2.7/shutil.py", line 250, in rmtree
    os.remove(fullname)
OSError: [Errno 13] Permission denied: '/usr/local/lib/python2.7/site-packages/web.py-0.40.dev0-py2.7.egg/EGG-INFO/dependency_links.txt'

I tried doing the same with sudo and I got this error.

pc7:~ mptorz$ sudo pip uninstall web.py
Password:
The directory '/Users/mptorz/Library/Caches/pip/http' or its parent directory is not owned by the current user and the cache has been disabled. Please check the permissions and owner of that directory. If executing pip with sudo, you may want sudo's -H flag.
Uninstalling web.py-0.40.dev0:
  /usr/local/lib/python2.7/site-packages/web.py-0.40.dev0-py2.7.egg
Proceed (y/n)? y
  Successfully uninstalled web.py-0.40.dev0
The directory '/Users/mptorz/Library/Caches/pip/http' or its parent directory is not owned by the current user and the cache has been disabled. Please check the permissions and owner of that directory. If executing pip with sudo, you may want sudo's -H flag.

Then I tried to do this:

pc7:~ mptorz$ sudo pip install web.py
The directory '/Users/mptorz/Library/Caches/pip/http' or its parent directory is not owned by the current user and the cache has been disabled. Please check the permissions and owner of that directory. If executing pip with sudo, you may want sudo's -H flag.
The directory '/Users/mptorz/Library/Caches/pip' or its parent directory is not owned by the current user and caching wheels has been disabled. check the permissions and owner of that directory. If executing pip with sudo, you may want sudo's -H flag.
Collecting web.py
  Downloading web.py-0.38.tar.gz (91kB)
    100% |████████████████████████████████| 92kB 199kB/s 
Installing collected packages: web.py
  Running setup.py install for web.py ... done
Successfully installed web.py-0.38

When I run the app I still get the same error 'ImportError: No module named web'.

I was asked to add the result of python -c "print(import('sys').path)":

pc7:~ mptorz$ python -c "print(__import__('sys').path)"
['', '/Library/Python/2.7/site-packages/pip-8.1.2-py2.7.egg', '/System/Library/Frameworks/Python.framework/Versions/2.7/lib/python27.zip', '/System/Library/Frameworks/Python.framework/Versions/2.7/lib/python2.7', '/System/Library/Frameworks/Python.framework/Versions/2.7/lib/python2.7/plat-darwin', '/System/Library/Frameworks/Python.framework/Versions/2.7/lib/python2.7/plat-mac', '/System/Library/Frameworks/Python.framework/Versions/2.7/lib/python2.7/plat-mac/lib-scriptpackages', '/System/Library/Frameworks/Python.framework/Versions/2.7/Extras/lib/python', '/System/Library/Frameworks/Python.framework/Versions/2.7/lib/python2.7/lib-tk', '/System/Library/Frameworks/Python.framework/Versions/2.7/lib/python2.7/lib-old', '/System/Library/Frameworks/Python.framework/Versions/2.7/lib/python2.7/lib-dynload', '/System/Library/Frameworks/Python.framework/Versions/2.7/Extras/lib/python/PyObjC', '/Library/Python/2.7/site-packages']

Somone also suggested trying "python -m pip install web.py" It resulted in this error:

pc7:~ mptorz$  python -m pip install web.py
Collecting web.py
  Downloading web.py-0.38.tar.gz (91kB)
    100% |████████████████████████████████| 92kB 215kB/s 
Installing collected packages: web.py
  Running setup.py install for web.py ... error
    Complete output from command /usr/bin/python -u -c "import setuptools, tokenize;__file__='/private/var/folders/w6/f08g43wn1zg6ny5b_lq414cr0000gn/T/pip-build-pn7SCD/web.py/setup.py';exec(compile(getattr(tokenize, 'open', open)(__file__).read().replace('\r\n', '\n'), __file__, 'exec'))" install --record /var/folders/w6/f08g43wn1zg6ny5b_lq414cr0000gn/T/pip-tBblX5-record/install-record.txt --single-version-externally-managed --compile:
    running install
    running build
    running build_py
    creating build
    creating build/lib
    creating build/lib/web
    copying web/__init__.py -> build/lib/web
    copying web/application.py -> build/lib/web
    copying web/browser.py -> build/lib/web
    copying web/db.py -> build/lib/web
    copying web/debugerror.py -> build/lib/web
    copying web/form.py -> build/lib/web
    copying web/http.py -> build/lib/web
    copying web/httpserver.py -> build/lib/web
    copying web/net.py -> build/lib/web
    copying web/python23.py -> build/lib/web
    copying web/session.py -> build/lib/web
    copying web/template.py -> build/lib/web
    copying web/test.py -> build/lib/web
    copying web/utils.py -> build/lib/web
    copying web/webapi.py -> build/lib/web
    copying web/webopenid.py -> build/lib/web
    copying web/wsgi.py -> build/lib/web
    creating build/lib/web/wsgiserver
    copying web/wsgiserver/__init__.py -> build/lib/web/wsgiserver
    copying web/wsgiserver/ssl_builtin.py -> build/lib/web/wsgiserver
    copying web/wsgiserver/ssl_pyopenssl.py -> build/lib/web/wsgiserver
    creating build/lib/web/contrib
    copying web/contrib/__init__.py -> build/lib/web/contrib
    copying web/contrib/template.py -> build/lib/web/contrib
    running install_lib
    creating /Library/Python/2.7/site-packages/web
    error: could not create '/Library/Python/2.7/site-packages/web': Permission denied

    ----------------------------------------
Command "/usr/bin/python -u -c "import setuptools, tokenize;__file__='/private/var/folders/w6/f08g43wn1zg6ny5b_lq414cr0000gn/T/pip-build-pn7SCD/web.py/setup.py';exec(compile(getattr(tokenize, 'open', open)(__file__).read().replace('\r\n', '\n'), __file__, 'exec'))" install --record /var/folders/w6/f08g43wn1zg6ny5b_lq414cr0000gn/T/pip-tBblX5-record/install-record.txt --single-version-externally-managed --compile" failed with error code 1 in /private/var/folders/w6/f08g43wn1zg6ny5b_lq414cr0000gn/T/pip-build-pn7SCD/web.py/

After doing everything I was advised here, I tried running the app again and I have got this:

pc7:~ mptorz$ python /Users/mptorz/webversion/bin/app.py http://0.0.0.0:8080/
Traceback (most recent call last):
  File "/Users/mptorz/webversion/bin/app.py", line 15, in <module>
    app.run()
  File "/Library/Python/2.7/site-packages/web/application.py", line 313, in run
    return wsgi.runwsgi(self.wsgifunc(*middleware))
  File "/Library/Python/2.7/site-packages/web/wsgi.py", line 55, in runwsgi
    server_addr = validip(listget(sys.argv, 1, ''))
  File "/Library/Python/2.7/site-packages/web/net.py", line 125, in validip
    port = int(port)
ValueError: invalid literal for int() with base 10: '//0.0.0.0:8080/'

I have just tried the home-brew solution suggested by @PhilipTzou. After I did that the output of running the app is:

pc7:~ mptorz$ python /Users/mptorz/webversion/bin/app.py http://0.0.0.0:8080/
Traceback (most recent call last):
  File "/Users/mptorz/webversion/bin/app.py", line 1, in <module>
    import web
  File "/usr/local/lib/python2.7/site-packages/web/__init__.py", line 14, in <module>
    import utils, db, net, wsgi, http, webapi, httpserver, debugerror
  File "/usr/local/lib/python2.7/site-packages/web/wsgi.py", line 8, in <module>
    import http
  File "/usr/local/lib/python2.7/site-packages/web/http.py", line 16, in <module>
    import net, utils, webapi as web
  File "/usr/local/lib/python2.7/site-packages/web/webapi.py", line 31, in <module>
    import sys, cgi, Cookie, pprint, urlparse, urllib
  File "/usr/local/Cellar/python/2.7.12/Frameworks/Python.framework/Versions/2.7/lib/python2.7/cgi.py", line 50, in <module>
    import mimetools
  File "/usr/local/Cellar/python/2.7.12/Frameworks/Python.framework/Versions/2.7/lib/python2.7/mimetools.py", line 6, in <module>
    import tempfile
  File "/usr/local/Cellar/python/2.7.12/Frameworks/Python.framework/Versions/2.7/lib/python2.7/tempfile.py", line 32, in <module>
    import io as _io
  File "/usr/local/Cellar/python/2.7.12/Frameworks/Python.framework/Versions/2.7/lib/python2.7/io.py", line 51, in <module>
    import _io
ImportError: dlopen(/usr/local/Cellar/python/2.7.12/Frameworks/Python.framework/Versions/2.7/lib/python2.7/lib-dynload/_io.so, 2): Symbol not found: __PyCodecInfo_GetIncrementalDecoder
  Referenced from: /usr/local/Cellar/python/2.7.12/Frameworks/Python.framework/Versions/2.7/lib/python2.7/lib-dynload/_io.so
  Expected in: flat namespace
 in /usr/local/Cellar/python/2.7.12/Frameworks/Python.framework/Versions/2.7/lib/python2.7/lib-dynload/_io.so

SOLUTION Finally, it worked. After running the solution suggested by @PhilipTzou and entering python /Users/mptorz/webversion/bin/app.py 8080 app.py is finally working and I can continue my python course. Thank you all for your help :)

Philip Tzou

According to the output of your sys.path, you are probably using OSX Python to run your script (app.py) but using Homebrew Python to execute PIP command. The solution is pretty simple:

brew link --overwrite python

This will change your default Python to Homebrew one. After executing this command, you can verify you are using Homebrew Python by typing this command: