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-bash: /usr/bin/yum: /usr/bin/python: bad interpreter: Permission denied

I am new in centos.I am try to do an application on it.For my application I need to install python 2.7.But the default one on server was python 2.6. So tried to upgrade the version .And accidentally I deleted the folder /usr/bin/python.After that I Installed python 2.7 through make install.I created the folder again /usr/bin/python and run command sudo ln -s /usr/bin/python2.7 /usr/bin/python. After this when I tried to run YUM commands I am getting the error
-bash: /usr/bin/yum: /usr/bin/python: bad interpreter: Permission denied
drwxrwxrwx 2 root root 4096 Mar 8 00:19 python
this is permission showing for the directory /usr/bin/python

CentOS requires that /usr/bin/python be pointed to Python 2.6, not any other version. Run the following commands:
sudo rm -rf /usr/bin/python
sudo ln -s /usr/bin/python2.6 /usr/bin/python
to at least fix that part of it. Next time you're building Python, use the defaults and install it to /usr/local/bin, not /usr/bin. That's what the /usr/local hierarchy is for - user-installed programs. /usr and /usr/bin should only be for system-installed programs (such as those installed by yum or its graphical equivalents), and you should keep out unless you know what you're doing. To use identically-named programs in /usr/local/bin instead of their counterparts in /usr/bin, open your ~/.bashrc or ~/.bash_profile (whichever your system uses) and add the following as the last line:
export PATH=/usr/local/bin:$PATH
Restart your shell session, and you should be all set.

yum doesn't work with python2.7.
You should do the following
vim /usr/bin/yum
change
#!/usr/bin/python
to
#!/usr/bin/python2.6
If your python2.6 was deleted, then reinstall them and point the directory in /usr/bin/yum to your python2.6 directory.

It is very simple; because the Python package was removed, the yum command won't work.
Please use below link to install packages:
Go to Link and download python package
wget http://mirror.centos.org/centos/7/sclo/x86_64/rh/python27/python27-1.1-26.1.el7.x86_64.rpm
rpm -ivh python27-1.1-26.1.el7.x86_64.rpm
Then yum will work.

this problem is that yum file start head write #!/usr/local/bin/python2.6， write binary file， is not dir， is python binary file

Resolution for CentOs 7:
dnf reinstall python-2.7.5-92.el7_9.x86_64
dnf reinstall yum
Remove python3 first using dnf if it is installed already.

-bash: /usr/bin/yum: /usr/bin/python: bad interpreter: Permission denied then
first remove python follow command line
-- sudo rpm -e python
second check which package install this command line
-- sudo rpm -q python
then install package
-- sudo yum install python*
i think this problem solve

My python installation is broken/corrupted. How do I fix it?

I followed these instructions on my RedHat Linux version 7 server (which originally just had Python 2.6.x installed):
beginning of instructions
install build tools
sudo yum install make automake gcc gcc-c++ kernel-devel git-core -y
install python 2.7 and change default python symlink
sudo yum install python27-devel -y
sudo rm /usr/bin/python
sudo ln -s /usr/bin/python2.7 /usr/bin/python
yum still needs 2.6, so write it in and backup script
sudo cp /usr/bin/yum /usr/bin/_yum_before_27
sudo sed -i s/python/python2.6/g /usr/bin/yum
sudo sed -i s/python2.6/python2.6/g /usr/bin/yum
should display now 2.7.5 or later:
python -V
end of instructions
The above commands and comments were taken from:
http://www.lecloud.net/post/61401763496/install-update-to-python-2-7-and-latest-pip-on
The python -v command returned this:
-bash: python: command not found
Now it is as if I have no Python installed. I don't want yum to break. I tried installing Python 3.4.
whereis python shows this:
python: /usr/bin/python2.6 /usr/bin/python2.6-config /usr/bin/python /usr/lib/python2.6 /usr/lib64/python2.6 /usr/local/bin/python2.7 /usr/local/bin/python3.4m-config /usr/local/bin/python2.7-config /usr/local/bin/python3.4 /usr/local/bin/python3.4m /usr/local/lib/python2.7 /usr/local/lib/python3.4 /usr/include/python2.6 /usr/share/man/man1/python.1.gz
What should I do now? I want a working installation of Python. For certain things I'm doing, I need it to be 2.7 or higher. I want yum to still work.

Do
sudo update-alternatives --remove-all python
sudo ln -sf /usr/bin/python2.7 /usr/bin/python

I got the same issue while upgrading ubuntu 18 to 19, this made it:
sudo rm /usr/bin/python
sudo ln -s /usr/bin/python2.7 /usr/bin/python
do-release-upgrade
From:
https://bugs.launchpad.net/ubuntu/+source/ubuntu-release-upgrader/+bug/1825655

For me, nothing worked except this one:
unlink /usr/bin/python3
ln -s /usr/bin/python3.7 /usr/bin/python3
Credit: https://josephgeis.dev/2020/04/upgrading-to-ubuntu-20-04-python3/

This is easily fixed by installing the python27 package via yum. It should install in /usr/bin, and may overwrite the /usr/bin/python symlink that should be pointing to 2.6. If it did (just run ls -l python* in /usr/bin to see), remove the symlink and point it back to 2.6. Next create a symlink for /usr/local/bin/python pointing at /usr/bin/python2.7. Finally, modify your ~/.bashrc or ~/.bash_profile (whichever you use) to have /usr/local/bin before /usr/bin in your PATH:
export PATH=/usr/local/bin:$PATH
at the very end of the file. This way, /usr/bin/python remains linked to Python 2.6, which is what the system expects, and when you run python at the command line it'll start up 2.7. You shouldn't have to make any changes to the yum script either - just blanket replacing python with python2.6 without understanding what you're doing is not a very good idea.
I'd also recommend installing Python 3.4 in /usr/local/bin if possible, where the binary will be named python3 by convention. Even if it installs in /usr/bin, you'll still have the choice of running python3 or python3.4 to specify which version you want. I work on a CentOS system that has each version of Python from 2.4 up to 3.4 installed, all in /usr/local/bin (I'm sure this was done manually, and not via yum), while the only python* in /usr/bin is 2.6. I couldn't find a python3 package for RedHat (I may not have been looking hard enough), so I'd recommend building the latest version from source (3.4.3 as of this writing). Unzip the tarball in a suitable directory, check out the README file, then, in the Python-3.4.3 directory, run ./configure --help to see what the options are, and if you need to change anything. As long as you have gcc installed, and don't need to link to any weird math libraries or anything, you should just be able to run:
./configure
make
make test
sudo make install
and it'll install to /usr/local/bin. Check the messages at the end of the make step, as it'll list any modules it wasn't able to build there. Fails usually happen because you don't have a required library installed, so look in setup.py in the base directory in the detect_modules() function (starting on line 449, and stretching all the way down to line 1564). Install both the lib and the -devel packages so you get the necessary headers.
This same process can also be followed if you want to install the latest 2.7.9, instead of RH's 2.7.5. One of the major (in my eyes) advantages of 2.7.9 is that pip is installed by default, making third-party module installation that much easier.
Good luck!

Is it possible to install another version of Python to Virtualenv?

I have a shared account in a web-hosting that has Python 2.4 installed, but my code is not compatible with 2.4. Is it possible to install Python 2.6 directly to Virtualenv?
Note: I don´t have permission to install it in the shared server.

Here are the options for virtualenv
$ virtualenv
You must provide a DEST_DIR
Usage: virtualenv [OPTIONS] DEST_DIR
Options:
--version show program's version number and exit.
-h, --help show this help message and exit.
-v, --verbose Increase verbosity.
-q, --quiet Decrease verbosity.
-p PYTHON_EXE, --python=PYTHON_EXE
The Python interpreter to use, e.g.,
--python=python2.5 will use the python2.5 interpreter
to create the new environment. The default is the
interpreter that virtualenv was installed with
(/usr/bin/python)
--clear Clear out the non-root install and start from scratch
--no-site-packages Don't give access to the global site-packages dir to
the virtual environment
--unzip-setuptools Unzip Setuptools or Distribute when installing it
--relocatable Make an EXISTING virtualenv environment relocatable.
This fixes up scripts and makes all .pth files
relative
--distribute Use Distribute instead of Setuptools. Set environ
variable VIRTUALENV_USE_DISTRIBUTE to make it the
default
--prompt==PROMPT Provides an alternative prompt prefix for this
environment
1) What you want to do is install python to a directory that you are able to write too.
You can follow the instructions here.
For Python 2.7.1
Python source
mkdir ~/src
mkdir ~/.localpython
cd ~/src
wget http://www.python.org/ftp/python/2.7.1/Python-2.7.1.tgz
tar -zxvf Python-2.7.1.tgz
cd Python-2.7.1
make clean
./configure --prefix=/home/${USER}/.localpython
make
make install
2) Install virtualenv
virtualenv source
cd ~/src
wget http://pypi.python.org/packages/source/v/virtualenv/virtualenv-1.5.2.tar.gz#md5=fbcefbd8520bb64bc24a560c6019a73c
tar -zxvf virtualenv-1.5.2.tar.gz
cd virtualenv-1.5.2/
~/.localpython/bin/python setup.py install
3) Create a virtualenv using your local python
virtualenv docs
mkdir /home/${USER}/virtualenvs
cd /home/${USER}/virtualenvs
~/.localpython/bin/virtualenv py2.7 --python=/home/${USER}/.localpython/bin/python2.7
4) Activate the environment
cd ~/virtualenvs/py2.7/bin
source ./activate
5) Check
(py2.7)$ python
Python 2.7.1 (r271:86832, Mar 31 2011, 15:31:37)
[GCC 4.4.5] on linux2
Type "help", "copyright", "credits" or "license" for more information.
>>> exit()
(py2.7)$ deactivate
$ python
Python 2.6.6 (r266:84292, Sep 15 2010, 15:52:39)
[GCC 4.4.5] on linux2
Type "help", "copyright", "credits" or "license" for more information.
>>>

Pre-requisites:
sudo easy_install virtualenv
sudo pip install virtualenvwrapper
Installing virtualenv with Python2.6:
You could manually download, build and install another version of Python to /usr/local or another location.
If it's another location other than /usr/local, add it to your PATH.
Reload your shell to pick up the updated PATH.
From this point on, you should be able to call the following 2 python binaries from your shell python2.5 and python2.6
Create a new instance of virtualenv with python2.6:
mkvirtualenv --python=python2.6 yournewenv

Now a days, the easiest way I found to have a more updated version of Python is to install it via conda into a conda environment.
Install conda(you may need a virtualenv for this)
pip install conda
Installing a new Python version inside a conda environent
I'm adding this answer here because no manual download is needed. conda will do that for you.
Now create an environment for the Python version you want. In this example I will use 3.5.2, because it it the latest version at this time of writing (Aug 2016).
conda create -n py35 python=3.5.2
Will create a environment for conda to install packages
To activate this environment(I'm assuming linux otherwise check the conda docs):
source activate py35
Now install what you need either via pip or conda in the environemnt(conda has better binary package support).
conda install <package_name>

Full guide with pyenv
If pyenv is not installed then install it with pyenv-installer:
$ curl https://pyenv.run | bash
To use any custom python version, e.g. 3.5.6 use the following:
pyenv install 3.5.6
pyenv virtualenv 3.5.6 NAME_OF_YOUR_ENV
cd YOUR_PROJECT_PATH
pyenv local NAME_OF_YOUR_ENV

The usual approach is to download the source and build and install locally (but not directly in virtualenv), and then create a new virtualenv using that local Python install. On some systems, it may be possible to download and install a prebuilt python, rather than building from source.

This procedure installs Python2.7 anywhere and eliminates any absolute path references within your env folder (managed by virtualenv). Even virtualenv isn't installed absolutely.
Thus, theoretically, you can drop the top level directory into a tarball, distribute, and run anything configured within the tarball on a machine that doesn't have Python (or any dependencies) installed.
Contact me with any questions. This is just part of an ongoing, larger project I am engineering. Now, for the drop...
Set up environment folders.
$ mkdir env
$ mkdir pyenv
$ mkdir dep
Get Python-2.7.3, and virtualenv without any form of root OS installation.
$ cd dep
$ wget http://www.python.org/ftp/python/2.7.3/Python-2.7.3.tgz
$ wget https://raw.github.com/pypa/virtualenv/master/virtualenv.py
Extract and install Python-2.7.3 into the pyenv dir. make clean is optional if you are doing this a 2nd, 3rd, Nth time...
$ tar -xzvf Python-2.7.3.tgz
$ cd Python-2.7.3
$ make clean
$ ./configure --prefix=/path/to/pyenv
$ make && make install
$ cd ../../
$ ls
dep env pyenv
Create your virtualenv
$ dep/virtualenv.py --python=/path/to/pyenv/bin/python --verbose env
Fix the symlink to python2.7 within env/include/
$ ls -l env/include/
$ cd !$
$ rm python2.7
$ ln -s ../../pyenv/include/python2.7 python2.7
$ cd ../../
Fix the remaining python symlinks in env. You'll have to delete the symbolically linked directories and recreate them, as above. Also, here's the syntax to force in-place symbolic link creation.
$ ls -l env/lib/python2.7/
$ cd !$
$ ln -sf ../../../pyenv/lib/python2.7/UserDict.py UserDict.py
[...repeat until all symbolic links are relative...]
$ cd ../../../
Test
$ python --version
Python 2.7.1
$ source env/bin/activate
(env)
$ python --version
Python 2.7.3
Aloha.

I'm using virtualenvwrapper and don't want to modify $PATH, here's how:
$ which python3
/usr/local/bin/python3
$ mkvirtualenv --python=/usr/local/bin/python3 env_name

You may use pyenv.
There are a lot of different versions anaconda, jython, pypy and so on...
https://github.com/yyuu/pyenv
Installation as simple as pyenv install 3.2.6
pyenv install --list
Available versions:
2.1.3
2.2.3
2.3.7
2.4
2.4.1
2.4.2
2.4.3
2.4.4
2.4.5
2.4.6
2.5
2.5.1
2.5.2
2.5.3
2.5.4
2.5.5
2.5.6
2.6.6
...

Although the question specifically describes installing 2.6, I would like to add some importants points to the excellent answers above in case someone comes across this. For the record, my case was that I was trying to install 2.7 on an ubuntu 10.04 box.
First, my motivation towards the methods described in all the answers here is that installing Python from deadsnake's ppa's has been a total failure. So building a local Python is the way to go.
Having tried so, I thought relying to the default installation of pip (with sudo apt-get install pip) would be adequate. This unfortunately is wrong. It turned out that I was getting all shorts of nasty issues and eventually not being able to create a virtualenv.
Therefore, I highly recommend to install pip locally with wget https://raw.github.com/pypa/pip/master/contrib/get-pip.py && python get-pip.py --user. This related question gave me this hint.
Now if this doesn't work, make sure that libssl-dev for Ubuntu or openssl-dev for CentOS is installed. Install them with apt-get or yum and then re-build Python (no need to remove anything if already installed, do so on top). get-pip complains about that, you can check so by running import ssl on a py shell.
Last, don't forget to declare .local/bin and local python to path, check with which pip and which python.

No, but you can install an isolated Python build (such as ActivePython) under your $HOME directory.
This approach is the fastest, and doesn't require you to compile Python yourself.
(as a bonus, you also get to use ActiveState's binary package manager)

I have not found suitable answer, so here goes my take, which builds upon #toszter answer, but does not use system Python (and you may know, it is not always good idea to install setuptools and virtualenv at system level when dealing with many Python configurations):
#!/bin/sh
mkdir python_ve
cd python_ve
MYROOT=`pwd`
mkdir env pyenv dep
cd ${MYROOT}/dep
wget https://pypi.python.org/packages/source/s/setuptools/setuptools-15.2.tar.gz#md5=a9028a9794fc7ae02320d32e2d7e12ee
wget https://raw.github.com/pypa/virtualenv/master/virtualenv.py
wget https://www.python.org/ftp/python/2.7.9/Python-2.7.9.tar.xz
xz -d Python-2.7.9.tar.xz
cd ${MYROOT}/pyenv
tar xf ../dep/Python-2.7.9.tar
cd Python-2.7.9
./configure --prefix=${MYROOT}/pyenv && make -j 4 && make install
cd ${MYROOT}/pyenv
tar xzf ../dep/setuptools-15.2.tar.gz
cd ${MYROOT}
pyenv/bin/python dep/virtualenv.py --no-setuptools --python=${MYROOT}/pyenv/bin/python --verbose env
env/bin/python pyenv/setuptools-15.2/setup.py install
env/bin/easy_install pip
echo "virtualenv in ${MYROOT}/env"
The trick of breaking chicken-egg problem here is to make virtualenv without setuptools first, because it otherwise fails (pip can not be found). It may be possible to install pip / wheel directly, but somehow easy_install was the first thing which came to my mind. Also, the script can be improved by factoring out concrete versions.
NB. Using xz in the script.

First of all, Thank you DTing for awesome answer. It's pretty much perfect.
For those who are suffering from not having GCC access in shared hosting, Go for ActivePython instead of normal python like Scott Stafford mentioned. Here are the commands for that.
wget http://downloads.activestate.com/ActivePython/releases/2.7.13.2713/ActivePython-2.7.13.2713-linux-x86_64-glibc-2.3.6-401785.tar.gz
tar -zxvf ActivePython-2.7.13.2713-linux-x86_64-glibc-2.3.6-401785.tar.gz
cd ActivePython-2.7.13.2713-linux-x86_64-glibc-2.3.6-401785
./install.sh
It will ask you path to python directory. Enter
../../.localpython
Just replace above as Step 1 in DTing's answer and go ahead with Step 2 after that. Please note that ActivePython package URL may change with new release. You can always get new URL from here : http://www.activestate.com/activepython/downloads
Based on URL you need to change the name of tar and cd command based on file received.

virtualenv --python=".localpython/bin/python2.7" env

Install cx_Oracle for Python

Am on Debian 5, I've been trying to install cx_oracle module for python without any success. First, I installed oracle-xe-client and its dependency (followed tutorial in the following link here).
Then, I used the scripts in /usr/lib/oracle/xe/app/oracle/product/10.2.0/client/bin to populate environment variables such as PATH, ORACLE_HOME and NLS_LANG.
Once, this was completed, I tried to run:
sudo easy_install cx_oracle
But I keep getting the following error:
Searching for cx-oracle
Reading http://pypi.python.org/simple/cx_oracle/
Reading http://cx-oracle.sourceforge.net
Reading http://starship.python.net/crew/atuining
Best match: cx-Oracle 5.0.4
Downloading http://prdownloads.sourceforge.net/cx-oracle/cx_Oracle-5.0.4.tar.gz?download
Processing cx_Oracle-5.0.4.tar.gz
Running cx_Oracle-5.0.4/setup.py -q bdist_egg --dist-dir /tmp/easy_install-xsylvG/cx_Oracle-5.0.4/egg-dist-tmp-8KoqIx
error: cannot locate an Oracle software installation
Any idea what I missed here?

The alternate way, that doesn't require RPMs. You need to be root.
Dependencies
Install the following packages:
apt-get install python-dev build-essential libaio1
Download Instant Client for Linux x86-64
Download the following files from Oracle's download site:
Extract the zip files
Unzip the downloaded zip files to some directory, I'm using:
/opt/ora/
Add environment variables
Create a file in /etc/profile.d/oracle.sh that includes
export ORACLE_HOME=/opt/ora/instantclient_11_2
export LD_LIBRARY_PATH=$LD_LIBRARY_PATH:$ORACLE_HOME
Create a file in /etc/ld.so.conf.d/oracle.conf that includes
/opt/ora/instantclient_11_2
Execute the following command
sudo ldconfig
Note: you may need to reboot to apply settings
Create a symlink
cd $ORACLE_HOME
ln -s libclntsh.so.11.1 libclntsh.so
Install cx_Oracle python package
You may install using pip
pip install cx_Oracle
Or install manually
Download the cx_Oracle source zip that corresponds with your Python and Oracle version. Then expand the archive, and run from the extracted directory:
python setup.py build
python setup.py install

I recommend that you grab the rpm files and install them with alien. That way, you can later on run apt-get purge no-longer-needed.
In my case, the only env variable I needed is LD_LIBRARY_PATH, so I did:
echo export LD_LIBRARY_PATH=/usr/lib/oracle/11.2/client/lib >> ~/.bashrc
source ~/.bashrc
I suppose in your case that path variable will be /usr/lib/oracle/xe/app/oracle/product/10.2.0/client/lib.

The following worked for me, both on mac and Linux. This one command should download needed additional files, without need need to set environment variables.
python -m pip install cx_Oracle --pre
Note, the --pre option is for development and pre-release of the Oracle driver. As of this posting, it was grabbing cx_Oracle-6.0rc1.tar.gz, which was needed. (I'm using python 3.6)

Thx Burhan Khalid, I overlooked your "You need to be root" quote, but found the way when you are not the root here.
At point 7 you need to use:
sudo env ORACLE_HOME=$ORACLE_HOME python setup.py install
Or
sudo env ORACLE_HOME=/path/to/instantclient python setup.py install

Thanks Burhan Khalid. Your advice to make a a soft link make my installation finally work.
To recap:
You need both the basic version and the SDK version of instant client
You need to set both LD_LIBRARY_PATH and ORACLE_HOME
You need to create a soft link (ln -s libclntsh.so.12.1 libclntsh.so in my case)
None of this is documented anywhere, which is quite unbelievable and quite frustrating. I spent over 3 hours yesterday with failed builds because I didn't know to create a soft link.

I think it may be the sudo has no access to get ORACLE_HOME.You can do like this.
sudo visudo
modify the text add
Defaults env_keep += "ORACLE_HOME"
then
sudo python setup.py build install

Alternatively you can install the cx_Oracle module without the PIP using the following steps
Download the source from here https://pypi.python.org/pypi/cx_Oracle
[cx_Oracle-6.1.tar.gz ]
Extract the tar using the following commands (Linux)
gunzip cx_Oracle-6.1.tar.gz
tar -xf cx_Oracle-6.1.tar
cd cx_Oracle-6.1
Build the module
python setup.py build
Install the module
python setup.py install

This just worked for me on Ubuntu 16:
Download ('instantclient-basic-linux.x64-12.2.0.1.0.zip' and 'instantclient-sdk-linux.x64-12.2.0.1.0.zip') from Oracle web site and then do following script (you can do piece by piece and I did as a ROOT):
apt-get install -y python-dev build-essential libaio1
mkdir -p /opt/ora/
cd /opt/ora/
## Now put 2 ZIP files:
# ('instantclient-basic-linux.x64-12.2.0.1.0.zip' and 'instantclient-sdk-linux.x64-12.2.0.1.0.zip')
# into /opt/ora/ and unzip them -> both will be unzipped into 1 directory: /opt/ora/instantclient_12_2
rm -rf /etc/profile.d/oracle.sh
echo "export ORACLE_HOME=/opt/ora/instantclient_12_2" >> /etc/profile.d/oracle.sh
echo "export LD_LIBRARY_PATH=$LD_LIBRARY_PATH:$ORACLE_HOME" >> /etc/profile.d/oracle.sh
chmod 777 /etc/profile.d/oracle.sh
source /etc/profile.d/oracle.sh
env | grep -i ora # This will check current ENVIRONMENT settings for Oracle
rm -rf /etc/ld.so.conf.d/oracle.conf
echo "/opt/ora/instantclient_12_2" >> /etc/ld.so.conf.d/oracle.conf
ldconfig
cd $ORACLE_HOME
ls -lrth libclntsh* # This will show which version of 'libclntsh' you have... --> needed for following line:
ln -s libclntsh.so.12.1 libclntsh.so
pip install cx_Oracle # Maybe not needed but I did it anyway (only pip install cx_Oracle without above steps did not work for me...)
Your python scripts are now ready to use 'cx_Oracle'... Enjoy!

This worked for me
python -m pip install cx_Oracle --upgrade
For details refer to the oracle quick start guide
https://cx-oracle.readthedocs.io/en/latest/installation.html#quick-start-cx-oracle-installation

If you are trying to install in MAC , just unzip the Oracle client which you downloaded and place it into the folder where you written python scripts.
it will start working.
There is too much problem of setting up environmental variables.
It worked for me.
Hope this helps.
Thanks

Try to reinstall it with the following code:
!pip install --proxy http://username:windowspwd#10.200.72.2:8080 --upgrade --force-reinstall cx_Oracle

If you require to install a specific version of cx_Oracle, like 7.3 which was the last version with support for Python 2, you can do the following:
python -m pip install cx_Oracle==7.3

Python: virtualenv - gtk-2.0

To add gtk-2.0 to my virtualenv I did the following:
$ virtualenv --no-site-packages --python=/usr/bin/python2.6 myvirtualenv
$ cd myvirtualenv
$ source bin/activate
$ cd lib/python2.6/
$ ln -s /usr/lib/pymodules/python2.6/gtk-2.0/
Virtualenv on Ubuntu with no site-packages
Now in the Python interpreter when I do import gtk it says: No module named gtk. When I start the interpreter with sudo it works.
Any reason why I need to use sudo and is there a way to prevent it?
Update:
Forgot to mention that cairo and pygtk work but it's not the one I need.
Update2:
Here the directory to show that I ain't crazy.
http://www.friendly-stranger.com/pictures/symlink.jpg

sudo python imports it just fine because that interpreter isn't using your virtual environment. So don't do that.
You only linked in one of the necessary items. Do the others mentioned in the answer to the question you linked as well.
(The pygtk.pth file is of particular importance, since it tells python to actually put that directory you linked onto the python path)
Update
Put that stuff in $VIRTUALENV/lib/python2.6/site-packages/ rather than the directory above that.
Looks like the .pth files aren't read from that directory - just from site-packages

This works for me (Ubuntu 11.10):
once you activate your virtualenv directory make sure 'dist-packages' exists:
mkdir -p lib/python2.7/dist-packages/
Then, make links:
For GTK2:
ln -s /usr/lib/python2.7/dist-packages/glib/ lib/python2.7/dist-packages/
ln -s /usr/lib/python2.7/dist-packages/gobject/ lib/python2.7/dist-packages/
ln -s /usr/lib/python2.7/dist-packages/gtk-2.0* lib/python2.7/dist-packages/
ln -s /usr/lib/python2.7/dist-packages/pygtk.pth lib/python2.7/dist-packages/
ln -s /usr/lib/python2.7/dist-packages/cairo lib/python2.7/dist-packages/
For GTK3:
ln -s /usr/lib/python2.7/dist-packages/gi lib/python2.7/dist-packages/

Remember to add a link to pygtk.py
ln -s /usr/lib/python2.7/dist-packages/pygtk.py lib/python2.7/dist-packages/

On Debian based Linux systems (Ubuntu, Mint) you can just install the ruamel.venvgtk package I put on PyPI. It will create the relevant links in your virtualenv during installation (if they are not yet there).
A more detailed explanation can be found in this answer

If it is not a requirement, that Python system packages are not used in the virtual environment, I would install apt install python-gtk2 (Ubuntu) and then create the virtual environment with:
virtualenv --system-site-packages .
That way, you do not pollute the system environment with your pip installations in the virtual environment, but reuse everything from the system. Especially pygtk.