Python unable to find lxml module

Python unable to find lxml module - python

I wrote a script some times ago that contain
from lxml import etree
But, unfortunatly it is not working anymore.
In doubt i checked installation with :
sudo apt-get install python-lxml
sudo pip install lxml
sudo apt-get install libxml2-dev
sudo apt-get install libxslt1-dev
I checked if it could be my python version with :
me#pc:~$ python
Python 2.7.3 (default, Sep 14 2012, 14:11:57)
[GCC 4.1.2 20061115 (prerelease) (Debian 4.1.1-21)] on linux2
Type "help", "copyright", "credits" or "license" for more information.
>>> import lxml
Traceback (most recent call last):
File "<stdin>", line 1, in <module>
ImportError: No module named lxml
My os is ubuntu 12.04.1 LTS with Python 2.7.3.
All seems fine. I can't see what could be the problem.

Your solution cited in edit, which use the xml.etree instead of lxml.etree is not the better way to do it, as these module have known incompatibilities, and mainly because lxml is certainly more optimised.
A good way to make a clean environment available is to use virtualenv :
$ virtualenv myproject
$ cd myproject
$ ./bin/pip install lxml # Repeat this with other dependencies
[wait for download and compiling]
Then, use ./bin/python to execute your script.
The advantages of this method are :
you can have different versions of dependencies between your system and your project
even if you break everything in your virtual environment, you will not compromised the rest of your system
you do not need root privileges to make an installation
As a reference, a more powerful but slightly more complex way to achieve this is to use buildout, but it can looks like hunting flies with a bazooka if you just want to execute a simple one-file script.

Solved the problem.
It seems that a software that i installed messed out my python path. The python that i was using when calling python in a terminal was the one installed by the software, and the one called by my script was the one installed on my system.
So, i just removed the python path of the software from the path variable of bash.

I had this problem when running tests in PyCharm. I could import lxml when using the terminal and virtual environment, but using the same virtual environment to run the tests resulted in the ImportError.
In my case upgrading from lxml 3.3.5 to 4.2.5 fixed the problem.

This likely has something do to with your Python environment. Here are three troubleshooting methods, from least to most cumbersome
1) Re-install via pip
pip uninstall lxml
pip install lxml
2) Re-Install via IDE
uninstalling it from the terminal (pip uninstall lxml)
adding from lxml import etree at the beginning of a python file
letting my IDE (PyCharm) show a missing import error
hovering over the error and installing it from the IDE via the error-fixing pop-up (not terminal)
3) Re-create virtualenv
Assuming you're working in a virtual environment (if not, shame to you and your family): delete and create a new environment.

if youre dealing with conda, i made the "discovery, that my conda install lxml does not work propperly after "successfully" installing
try uninstalling and reinstalling with pip, that worked for me
conda remove lxml
pip install lxml

For Python 3.6, it is very tricky.
I have the same problem and try to install the latest version, lxml 3.8. But I still get the error. And then I use lxml 3.7.3, then it is ok.

Related

cannot use pyperclip module in python shell after successful download [duplicate]

During the past years, I have installed many Python libraries with various Python versions. To make them ready to work immediately, I installed them blindly without control. Currently they're causing problems when I tried to install pynest which invokes numpy, scipy and matplotlib. After struggling, I am going to clean and reinstall Python and the libraries.
After investigation, I found Python 2.5/2.6/2.7/3.2 on my system, and each of them has some copies or other things at: (my OS == Mac OS X 10.7.5 Lion)
/Library/Frameworks/
/opt/local/Library/Frameworks/
/opt/local/bin/
/Applications/
/usr/local/bin/
/usr/bin/
/System/Library/Frameworks/
I know I'm crazy to have these. Now I have removed all these except the things in /System/Libarary/Frameworks (I never remove any thing from /System/Library/). After the clean work, which python now gives /usr/bin/python which links to /System/Library/Frameworks.
Now, is it a clear environment for me to reinstall python? How to double check that there's no other versions existing? How should I reinstall them to guarantee that they and their libraries won't be everywhere and have many copies again?
I want to install a clean Python 2.7 onto a proper location, and make my system know exactly where it is and never install any libraries somewhere else. Please give me some advice that how to manage it like in a professional way.
For your information, here is my current $PATH, I think it should be modified:
/opt/local/bin:/opt/local/sbin:/opt/nest/lib/python2.7/site-packages:/usr/local/lib/python2.7/site-packages:/Library/Frameworks/Python.framework/Versions/2.7/bin:/usr/texbin:/Library/Frameworks/Python.framework/Versions/3.2/bin:/usr/bin:/bin:/usr/sbin:/sbin:/usr/local/bin:/usr/texbin:/Library/Frameworks/Python.framework/Versions/3.2/lib/python3.2/site-packages/django/bin:/usr/X11/bin:/opt/local/bin:/opt/local/sbin:/usr/local/lib/python2.7/site-packages:/Library/Frameworks/Python.framework/Versions/2.7/bin:/Library/Frameworks/Python.framework/Versions/3.2/bin
Please let me know If you need more information. Thank you!
UPDATE:
I'm rethinking profoudly why it becomes so crazy. I believe it's because I installed things via:
easy_install / macports / homebrew / fink / pip sometimes;
.dmg sometimes;
.pkg sometimes;
compile source code sometimes;
and they made things at different locations. I wonder what's the mechanism behind these ways? How do they choose target location? How to prevent them from messing things up?

Why did it get messed up?
There're a couples of different way to install Python, as the update of OP says, and they locate files in different locations. For example, macports puts things into /opt/local/, while homebrew puts things into /usr/local/. Also, Mac OS X brings a few python versions with itself. So, if you install python many times via different ways, you will get many python versions existing independently on your system.
What problem does it cause?
I don't know exactly. I guess the problem is that if you have many versions of python, then which one to use and where to find packages will be determined by the path order in your system PATH and the PYTHONPATH respectively. So you may lose control of where to install python modules. Consider that if you run sudo python setup.py install to install a module (it finds python by the root's PATH) and then try to import the module by python -c "import it" (this time it finds python by your PATH), maybe something will go wrong. This is my guess, I didn't validate it. But in my own case, something did go wrong.
How to avoid this?
I think the principle would be that be aware of that different ways and tools install things independently to different locations, so use them mindfully.
Unless you intend to, don't install the same thing twice via different
ways. (If you intend to do it for python, you might want to check out virtualenv)
Keep an eye on the path order in your PATH and consider if it's
correct.
When installing modules, be clear which python (or pip) is
running and where the module is installed.
So, how did I solve my own case?
Since it had been messing up already and seemed to be very hard to cure, so finally I solved this question by a full OS re-installation, and started to follow the DOs-and-DONTs above. For the installation of the scientific environment with python (numpy/scipy/matplotlib, which had shown problems to make me ask this question), I found this tutorial was extremely helpful. So, problem solved finally.

Here is what was confusing me and how I solved it.
$ which python
/usr/bin/python
$ which python3
/usr/local/bin/python3
$ ls /usr/local/bin/python
ls: /usr/local/bin/python: No such file or directory
So notice I didn't have a HomeBrew installation of python2.7, but did have the python3 installation. The version under /usr/bin/python is using the system default. You can tell based on the module search path:
$ /usr/bin/python
Python 2.7.10 (default, Feb 7 2017, 00:08:15)
[GCC 4.2.1 Compatible Apple LLVM 8.0.0 (clang-800.0.34)] on darwin
`enter code here`Type "help", "copyright", "credits" or "license" for
more information.
>>> import sys
>>> sys.path
['', '/Library/Python/2.7/...
Notice the '/Library/Python'... that's Mac OS's version of python. But I want to stay strictly on a user installed version (i.e. HomeBrew).
So here's what I did to fix this:
$ brew install python
...
Warning: python 2.7.13 is already installed, it's just not linked.
You can use `brew link python` to link this version.
$ brew link --overwrite python
$ which python
/usr/local/bin/python
$ python
Python 2.7.10 (default, Feb 7 2017, 00:08:15)
[GCC 4.2.1 Compatible Apple LLVM 8.0.0 (clang-800.0.34)] on darwin
Type "help", "copyright", "credits" or "license" for more information.
>>> import sys
>>> sys.path
['', '/usr/local/Cellar/python/2.7.13...
Its no longer /Library/.. but /usr/local.
Now its finding all of my pip installed modules! Problem solved!
UPDATE:
After updating brew to version 1.5.4, it seems the symbolic links were removed. And now you have to add this to your path:
export PATH="/usr/local/opt/python/libexec/bin:$PATH"
Read the Caveats section in 'brew info python':
==> Caveats
This formula installs a python2 executable to /usr/local/bin.
If you wish to have this formula's python executable in your PATH then add
the following to ~/.bash_profile:
export PATH="/usr/local/opt/python/libexec/bin:$PATH"
Pip and setuptools have been installed. To update them
pip2 install --upgrade pip setuptools
You can install Python packages with
pip2 install <package>
They will install into the site-package directory
/usr/local/lib/python2.7/site-packages
See: https://docs.brew.sh/Homebrew-and-Python.html

In order to install a python distributions into specific folder, you can use the --prefix scheme during python installation. Using the prefix scheme, you can for example install Python 2.7 into the folder /opt/py27. Now, in order to use the new installed Python distribution you have to: cleanup you PATH and LD_LIBRARY_PATH:
Remove all 'old' Python paths and
configure (according to my example) the environment variables like this:
PATH: Add /opt/py27/bin
LD_LIBRARY_PATH: Add /opt/py27/lib
That's it.
(In case you need multiple environments of Python installed at the same time, I'd suggest to have a look at virtualenv)

tl;dr
brew install python
Symptoms
I had similar issues with python programs not finding dependencies.
My python3 version was a broken symlink.
My pip was pointing to a python 3.8
And my pip3 was pointing to 3.9
python -V was outputting some python 2.7 version
python3 -V was outputting some python3.8 version
Solution
I ran brew install python and it fixed all my problems.

pip installed module but python gives Import error [duplicate]

Here is what was confusing me and how I solved it.
$ which python
/usr/bin/python
$ which python3
/usr/local/bin/python3
$ ls /usr/local/bin/python
ls: /usr/local/bin/python: No such file or directory
So notice I didn't have a HomeBrew installation of python2.7, but did have the python3 installation. The version under /usr/bin/python is using the system default. You can tell based on the module search path:
$ /usr/bin/python
Python 2.7.10 (default, Feb 7 2017, 00:08:15)
[GCC 4.2.1 Compatible Apple LLVM 8.0.0 (clang-800.0.34)] on darwin
`enter code here`Type "help", "copyright", "credits" or "license" for
more information.
>>> import sys
>>> sys.path
['', '/Library/Python/2.7/...
Notice the '/Library/Python'... that's Mac OS's version of python. But I want to stay strictly on a user installed version (i.e. HomeBrew).
So here's what I did to fix this:
$ brew install python
...
Warning: python 2.7.13 is already installed, it's just not linked.
You can use `brew link python` to link this version.
$ brew link --overwrite python
$ which python
/usr/local/bin/python
$ python
Python 2.7.10 (default, Feb 7 2017, 00:08:15)
[GCC 4.2.1 Compatible Apple LLVM 8.0.0 (clang-800.0.34)] on darwin
Type "help", "copyright", "credits" or "license" for more information.
>>> import sys
>>> sys.path
['', '/usr/local/Cellar/python/2.7.13...
Its no longer /Library/.. but /usr/local.
Now its finding all of my pip installed modules! Problem solved!
UPDATE:
After updating brew to version 1.5.4, it seems the symbolic links were removed. And now you have to add this to your path:
export PATH="/usr/local/opt/python/libexec/bin:$PATH"
Read the Caveats section in 'brew info python':
==> Caveats
This formula installs a python2 executable to /usr/local/bin.
If you wish to have this formula's python executable in your PATH then add
the following to ~/.bash_profile:
export PATH="/usr/local/opt/python/libexec/bin:$PATH"
Pip and setuptools have been installed. To update them
pip2 install --upgrade pip setuptools
You can install Python packages with
pip2 install <package>
They will install into the site-package directory
/usr/local/lib/python2.7/site-packages
See: https://docs.brew.sh/Homebrew-and-Python.html

In order to install a python distributions into specific folder, you can use the --prefix scheme during python installation. Using the prefix scheme, you can for example install Python 2.7 into the folder /opt/py27. Now, in order to use the new installed Python distribution you have to: cleanup you PATH and LD_LIBRARY_PATH:
Remove all 'old' Python paths and
configure (according to my example) the environment variables like this:
PATH: Add /opt/py27/bin
LD_LIBRARY_PATH: Add /opt/py27/lib
That's it.
(In case you need multiple environments of Python installed at the same time, I'd suggest to have a look at virtualenv)

tl;dr
brew install python
Symptoms
I had similar issues with python programs not finding dependencies.
My python3 version was a broken symlink.
My pip was pointing to a python 3.8
And my pip3 was pointing to 3.9
python -V was outputting some python 2.7 version
python3 -V was outputting some python3.8 version
Solution
I ran brew install python and it fixed all my problems.

matplotlib error - no module named tkinter

I tried to use the matplotlib package via Pycharm IDE on windows 10.
when I run this code:
from matplotlib import pyplot
I get the following error:
ImportError: No module named 'tkinter'
I know that in python 2.x it was called Tkinter, but that is not the problem - I just installed a brand new python 3.5.1.
EDIT: in addition, I also tried to import 'tkinter' and 'Tkinter' - neither of these worked (both returned the error message I mentioned).

For Linux
Debian based distros:
sudo apt-get install python3-tk
RPM based distros:
sudo yum install python3-tkinter
For windows:
For Windows, I think the problem is you didn't install complete Python package. Since Tkinter should be shipped with Python out of box. See: http://www.tkdocs.com/tutorial/install.html . Good python distributions for Windows can be found by the companies Anaconda or ActiveState.
Test the python module
python -c "import tkinter"
p.s. I suggest installing ipython, which provides powerful shell and necessary packages as well.

you can use
import matplotlib
matplotlib.use('agg')
import matplotlib.pyplot as plt
if you dont want to use tkinter at all.
Also dont forget to use %matplotlib inline at the top of your notebook if using one.
EDIT: agg is a different backend like tkinter for matplotlib.

For Windows users, there's no need to download the installer again. Just do the following:
Go to start menu, type Apps & features,
Search for "python" in the search box,
Select the Python version (e.g. Python 3.8.3rc1(32-bit)) and click Modify,
On the Modify Setup page click Modify,
Tick td/tk and IDLE checkbox (which installs tkinter) and click next.
Wait for installation and you're done.

On Centos, the package names and commands are different. You'll need to do:
sudo yum install tkinter
To fix the problem.

Almost all answers I searched for this issue say that Python on Windows comes with tkinter and tcl already installed, and I had no luck trying to download or install them using pip, or actviestate.com site. I eventually found that when I was installing python using the binary installer, I had unchecked the module related to TCL and tkinter. So, I ran the binary installer again and chose to modify my python version by this time selecting this option. No need to do anything manually then. If you go to your python terminal, then the following commands should show you version of tkinter installed with your Python:
import tkinter
import _tkinter
tkinter._test()

If you are using fedora then first install tkinter
sudo dnf install python3-tkinter
I don't think you need to import tkinter afterwards
I also suggest you to use virtualenv
$ python3 -m venv myvenv
$ source myvenv/bin/activate
And add the necessary packages using pip

On CentOS 7 and Python 3.4, the command is sudo yum install python34-tkinter
On Redhat 7.4 with Python 3.6, the command is sudo yum install rh-python36-python-tkinter

For windows users, re-run the installer. Select Modify. Check the box for tcl/tk and IDLE. The description for this says "Installs tkinter"

On Ubuntu, early 2018, there is no python3.6-tk on ubuntu's (xenial/16.04) normal distributions, so even if you have earlier versions of python-tk this won't work.
My solution was to use set everything up with python 3.5:
sudo apt install python3.5-tk
virtualenv --python=`which python3.5` python-env
source python-env/bin/activate
pip install -r requirements.txt
And now matplotlib can find tkinter.
EDIT:
I just needed 3.6 afterall, and the trick was to:
sudo apt install tk-dev
and then rebuild python3.6, after tk-dev, eg:
./configure
make
make install

If you are using python 3.6, this worked for me:
sudo apt-get install python3.6-tk
instead of
sudo apt-get install python3-tk
Which works for other versions of python3

For the poor guys like me using python 3.7. You need the python3.7-tk package.
sudo apt install python3.7-tk
$ python
Python 3.7.4 (default, Sep 2 2019, 20:44:09)
[GCC 5.4.0 20160609] on linux
Type "help", "copyright", "credits" or "license" for more information.
>>> import tkinter
Traceback (most recent call last):
File "<stdin>", line 1, in <module>
ModuleNotFoundError: No module named 'tkinter'
>>> exit()
Note. python3-tk is installed. But not python3.7-tk.
$ sudo apt install python3.7-tk
Reading package lists... Done
Building dependency tree
Reading state information... Done
Suggested packages:
tix python3.7-tk-dbg
The following NEW packages will be installed:
python3.7-tk
0 upgraded, 1 newly installed, 0 to remove and 34 not upgraded.
Need to get 143 kB of archives.
After this operation, 534 kB of additional disk space will be used.
Get:1 http://ppa.launchpad.net/deadsnakes/ppa/ubuntu xenial/main amd64 python3.7-tk amd64 3.7.4-1+xenial2 [143
kB]
Fetched 143 kB in 0s (364 kB/s)
Selecting previously unselected package python3.7-tk:amd64.
(Reading database ... 256375 files and directories currently installed.)
Preparing to unpack .../python3.7-tk_3.7.4-1+xenial2_amd64.deb ...
Unpacking python3.7-tk:amd64 (3.7.4-1+xenial2) ...
Setting up python3.7-tk:amd64 (3.7.4-1+xenial2) ...
After installing it, all good.
$ python3
Python 3.7.4 (default, Sep 2 2019, 20:44:09)
[GCC 5.4.0 20160609] on linux
Type "help", "copyright", "credits" or "license" for more information.
>>> import tkinter
>>> exit()

On CentOS 6.5 with python 2.7 I needed to do: yum install python27-tkinter

Sometimes (for example in osgeo4w distribution) tkinter is removed.
Try changing matplotlib backend editing matplotlibrc file located in [python install dir]/matplotlib/mpl-data/matplotlibrc changing The backend parameter from backend: TkAgg to something other like backend: Qt4Aggas described here: http://matplotlib.org/faq/usage_faq.html#what-is-a-backend

Since I'm using Python 3.7 on Ubuntu I had to use:
sudo apt-get install python3.7-tk

Maybe you installed python from source. In this case, you can recompile python with tcl/tk supported.
Complie and install tcl/tk from http://www.tcl.tk/software/tcltk/download.html, I'll suppose you installed python at /home/xxx/local/tcl-tk/.
# install tcl
wget -c https://prdownloads.sourceforge.net/tcl/tcl8.6.9-src.tar.gz
tar -xvzf tcl8.6.9-src.tar.gz
cd tcl8.6.9
./configure --prefix=/home/xxx/local/tcl-tk/
make
make install
# install tk
wget -c https://prdownloads.sourceforge.net/tcl/tk8.6.9.1-src.tar.gz
tar -xvzf tk8.6.9.1-src.tar.gz
cd tk8.6.9.1
./configure --prefix=/home/xxx/local/tcl-tk/
make
make install
Recompile python with tcl/tk supported, for example:
# download the source code of python and decompress it first.
cd <your-python-src-dir>
./configure --prefix=/home/xxx/local/python \
--with-tcltk-includes=/home/xxx/local/tcl-tk/include \
--with-tcltk-libs=/home/xxx/local/tcl-tk/lib
make
make install

I had the same issue on Win x86/64 because my custom Python3.7 installation did not include Tcl packages, so just modify or re-install your python
https://www.python.org/downloads/release/python-370/

Download Python Setup file and click modify then tick the tcl/tk and install.
After installation is complete go to folder where python is installed ( Default is C:\Users*Your username*\AppData\Local\Programs\Python\Python39\Lib) .
Copy the tkinter folder and paste it in the lib folder of your pycharm project.
Error should be resolved

Follow these steps to easily install Tkinter on your PyCharm IDE:
First go to the File:
Second is go to New Project Setup > Settings for new projects:
And then click the Settings for new projects and you'll get redirected in here:
Please click the + symbol in there:
after that install future and there you go...

If you’re having pip(which you probably do), open up cmd or powershell on Windows or a terminal window on OS X or Linux and try this(make sure python is in the system path if you’re on Windows):
pip install tkinter
It should take a while to install tkinter, and then try to execute this code block:
from tkinter import *
root = Tk()
# Your code goes here
root.mainloop()
Hope that this helps! Thank you!

Installing VTK for Python

I'm trying to install VTK module for python, I am however unsuccesful in doing so. I have downloaded a VTK tar-file, but I'm unable to extract it. I'm capable of extracting other tar-files, so there must be something specific with this file I suppose.
This is my error:
gzip: stdin: invalid compressed data--format violated
tar: Child returned status 1
tar: Error is not recoverable: exiting now
I hope somebody can help me with this.

The answer depends on the operating system you are using. This will be a lot easier if you can find a package or installer for your specific operating system and/or distribution.
Linux
If you are using Linux then look for the corresponding package in the distribution's package manager. For example, on Ubuntu Linux you should be able to install it using the following command:
sudo apt-get install python-vtk
Microsoft Windows
If you are using Microsoft Windows, the easiest way would be to install Python(x,y). It comes with VTK support.
Additionally, Anaconda also includes VTK package as well as support for virtual environments. It might be a good option for some folks.
Mac OS X
If you are using Mac OS X, try installing everything via MacPorts.
As #Nil mentioned in comments below, a standalone python interface to VTK is now provided by VTK developers. You may download it for Windows, Darwin, and Linux from here.
As mentioned by #Nil, VTK used to offer vtkpython binaries on their download page. However, they've dropped this since VTK-8.x.x as mentioned here:
Sorry, about that. We decided to drop the vtkpython binaries for 8. I want to focus our energies on supporting python wheel installs instead. There’s no timeline yet for a complete solution but we’ve made some good progress toward that recently here: https://github.com/jcfr/VTKPythonPackage.
Thus, the recommended way of installing vtkpython now is (see this page):
$ python -m pip install --upgrade pip
$ python -m pip install vtk

on Ubuntu, maybe this post will be helpful:
http://kazenotaiyo.blogspot.jp/2010/06/installing-vtk-in-ubuntu-and-making.html
The easiest way
The first and easiest is to just install the packages with the Aptitude Package Manager:
sudo apt-get install libvtk5-dev python-vtk
If you want the newest version
If you want the newest version VTK, you can also build it yourself:
Make sure CMake is installed:
sudo apt-get install cmake
Download the VTK source from the Downloads page.
Untar it:
tar xvzf vtk-5.6.0.tar.gz
Create an Out-Of-Source build and configure with CMake:
mkdir VTK_BUILD
cd VTK_BUILD
ccmake ../VTK
Make sure you enable python wrapping and set your install prefix to where you want the package to go. The default /usr/local works fine.
sudo make -j 8 install
(the -j 8 for make just makes the build process parallel assuming you've got the processors for it)
You now have VTK installed. Congrats! if you try to run vtkpython though, you'll get an error:
vtkpython: error while loading shared libraries: libvtksys.so.5.6: cannot open shared object file: No such file or directory
To fix this, append these lines to your .bash_profile, .bashrc, or .profile file in your home directory:
# add vtk paths
LD_LIBRARY_PATH="$LD_LIBRARY_PATH:/usr/local/lib/vtk-5.6"
PYTHONPATH="$PYTHONPATH:/usr/local/lib/vtk-5.6"
You'll need to reset your terminal now.
That sets up your library and python paths for the vtkpython executable.

http://www.lfd.uci.edu/~gohlke/pythonlibs/#vtk Try this! Works for windows !

I have installed vtk without a problem under win7 via pip:
> pip install vtk
Collecting vtk
Downloading vtk-8.1.0-cp36-cp36m-win_amd64.whl (24.4MB)
100% |████████████████████████████████| 24.4MB 56kB/s
Installing collected packages: vtk
Successfully installed vtk-8.1.0
With Anacond python:
> python
Python 3.6.1 |Continuum Analytics, Inc.| (default, May 11 2017, 13:25:24) [MSC v.1900 64 bit (AMD64)] on win32
Type "help", "copyright", "credits" or "license" for more information.

MacOS only:
See How to Install Mayavi on MacOS
An abridged version of this for MacOS is the following: (but I recommend the full procedure based on above link, but note that it installs Mayavi too)
The following steps seem to work on MacOS:
brew install vtk
pip install vtk
This installs vtk#9.1. You may want to install brew install vtk#8.2 instead.
Tested on:
Python: 3.9.13, MacOS: 12.4 Monterey
PS. As mentioned before, this answer may be incomplete (you may need QT too, bu tI am not sure). For a complete one including Mayavi, see My answer here . I suggest following the steps there.
I didn't update all content s here because I am not sure which steps are required if you only need VTK (not Mayavi). For example, I don't know whether you need QT or not.

What is causing ImportError: No module named pkg_resources after upgrade of Python on os X?

I just updated Python to 2.6.4 on my Mac.
I installed from the dmg package.
The binary did not seem to correctly set my Python path, so I added '/usr/local/lib/python2.6/site-packages' in .bash_profile
>>> pprint.pprint(sys.path)
['',
'/Users/Bryan/work/django-trunk',
'/usr/local/lib/python2.6/site-packages',
'/Library/Frameworks/Python.framework/Versions/2.6/lib/python26.zip',
'/Library/Frameworks/Python.framework/Versions/2.6/lib/python2.6',
'/Library/Frameworks/Python.framework/Versions/2.6/lib/python2.6/plat-darwin',
'/Library/Frameworks/Python.framework/Versions/2.6/lib/python2.6/plat-mac',
'/Library/Frameworks/Python.framework/Versions/2.6/lib/python2.6/plat-mac/lib-scriptpackages',
'/Library/Frameworks/Python.framework/Versions/2.6/lib/python2.6/lib-tk',
'/Library/Frameworks/Python.framework/Versions/2.6/lib/python2.6/lib-old',
'/Library/Frameworks/Python.framework/Versions/2.6/lib/python2.6/lib-dynload',
'/Library/Frameworks/Python.framework/Versions/2.6/lib/python2.6/site-packages']
Apparently that is not all the required paths because I can't run iPython.
$ ipython
Traceback (most recent call last):
File "/usr/local/bin/ipython", line 5, in <module>
from pkg_resources import load_entry_point
ImportError: No module named `pkg_resources`
I've done Google searches and I can't really figure out how to install pkg_resources or make sure it's on the path.
What do I need to do to fix this?

I encountered the same ImportError. Somehow the setuptools package had been deleted in my Python environment.
To fix the issue, run the setup script for setuptools:
curl https://bitbucket.org/pypa/setuptools/raw/bootstrap/ez_setup.py | python
If you have any version of distribute, or any setuptools below 0.6, you will have to uninstall it first.*
See Installation Instructions for further details.
* If you already have a working distribute, upgrading it to the "compatibility wrapper" that switches you over to setuptools is easier. But if things are already broken, don't try that.

[UPDATE] TL;DR pkg_resources is provided by either Distribute or setuptools.
[UPDATE 2] As announced at PyCon 2013, the Distribute and setuptools projects have re-merged. Distribute is now deprecated and you should just use the new current setuptools. Try this:
curl -O https://bitbucket.org/pypa/setuptools/raw/bootstrap/ez_setup.py
python ez_setup.py
Or, better, use a current pip as the high level interface and which will use setuptools under the covers.
[Longer answer for OP's specific problem]:
You don't say in your question but I'm assuming you upgraded from the Apple-supplied Python (2.5 on 10.5 or 2.6.1 on 10.6) or that you upgraded from a python.org Python 2.5. In any of those cases, the important point is that each Python instance has its own library, including its own site-packages library, which is where additional packages are installed. (And none of them use /usr/local/lib by default, by the way.) That means you'll need to install those additional packages you need for your new python 2.6. The easiest way to do this is to first ensure that the new python2.6 appears first on your search $PATH (that is, typing python2.6 invokes it as expected); the python2.6 installer should have modified your .bash_profile to put its framework bin directory at the front of $PATH. Then install easy_install using setuptools following the instructions there. The pkg_resources module is also automatically installed by this step.
Then use the newly-installed version of easy_install (or pip) to install ipython.
easy_install ipython
or
pip install ipython
It should automatically get installed to the correct site-packages location for that python instance and you should be good to go.

In case of upgrading your python on mac os 10.7 and pkg_resources doesn't work, the simplest way to fix this is just reinstall setuptools as Ned mentioned above.
sudo pip install setuptools --upgrade
or sudo easy_install install setuptools --upgrade

On my system (OSX 10.6) that package is at
/System/Library/Frameworks/Python.framework/Versions/2.6/Extras/lib/python/pkg_resources.py
I hope that helps you figure out if it's missing or just not on your path.

The reason might be because the IPython module is not in your PYTHONPATH.
If you donwload IPython and then do
python setup.py install
The setup doesn't add the module IPython to your python path.
You might want to add it to your PYTHONPATH manually. It should work after you do :
export PYTHONPATH=/pathtoIPython:$PYTHONPATH
Add this line in your .bashrc or .profile to make it permanent.

I realize this is not related to OSX, but on an embedded system (Beagle Bone Angstrom) I had the exact same error message. Installing the following ipk packages solved it.
opkg install python-setuptools
opkg install python-pip

I got this error on Ubuntu, and the following worked for me:
Removed the dropbox binaries and download them again, by running:
sudo rm -rf /var/lib/dropbox/.dropbox-dist
dropbox start -i

I encountered with the same problem when i am working on autobahn related project.
1) So I download the setuptools.-0.9.8.tar.gz form https://pypi.python.org/packages/source/s/setuptools/ and extract it.
2 )Then i get the pkg_resources module and copy it to the folder where it needed.
**in my case that folder was C:\Python27\Lib\site-packages\autobahn

In my case, package python-pygments was missed. You can fix it by command:
sudo apt-get install python-pygments
If there is problem with pandoc. You should install pandoc and pandoc-citeproc.
sudo apt-get install pandoc pandoc-citeproc

Try this only if you are ok with uninstalling python.
I uninstalled python using
brew uninstall python
then later installed using
brew install python
then it worked!

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