Problem installing Python-Dev

This bit:

 python2.7-dev : Depends: python2.7 (= 2.7.3-0ubuntu3) but 2.7.3-0ubuntu3.1 is to be installed

suggests that you are using some mismatched repositories, or have some apt-pins in place keeping the version dependencies from lining up. I think, specifically, python-2.7 2.7.3-0ubuntu3.1 is in the Precise-proposed repository and the 2.7.3-0ubuntu3 version is in Precise/main proper, so you may be preferring -proposed for some but not all packages.

Can you edit your question to include the output of:

apt-cache policy python2.7-dev
apt-cache policy python2.7

and maybe:

apt-cache show python2.7

...

Reading the apt-cache output from your pastebin, it looks like you have the python2.7 2.7.3-0ubuntu3.1 from precise-updates/main installed, but python2.7-dev is from precise/main. I think your install media or an earlier "apt-get update" included the precise-updates repository, but it's not in your current sources.list.

I think you'll be able to get the install going after adding precise-updates and then apt-get update.

echo "deb http://us.archive.ubuntu.com/ubuntu/ precise-updates main restricted" | sudo tee -a /etc/apt/sources.list.d/precise-updates.list
sudo apt-get update
sudo apt-get install python2.7-dev

You shouldn't install numpy with pip, use the package Ubuntu provides:

dennis@koekblik:~$ apt-cache show python-numpy
Package: python-numpy
Priority: optional
Section: python
Installed-Size: 7616
...

As to your actual problem: try installing python2.7-dev. It will likely fail but should give you a better error message.

fastest solution:

• Install (sudo apt-get install synaptic) Synaptic Package Manager and start it
• Click on Settings-Repositories
• Select Download from: Main Server
• Click Close then click on Reload.
• Mark python-dev for installation and Synaptic will also mark all dependencies of python-dev (libexpat1-dev, libssl-dev, libssl-doc, python2.7-dev, zlib1g-dev).

I have just resolved the same problem on freshly installed Ubuntu x86 12.04.3.