For what I've read I need Python-Dev, how do I install it on OSX?

I think the problem I have, is, my Xcode was not properly installed, and I don't have the paths where I should.

This previous question:

http://stackoverflow.com/questions/2685887/where-is-gcc-on-osx-i-have-installed-xcode-already

Was about I couldn't find gcc, now I can't find Python.h

Should I just link my /Developer directory to somewhere else in /usr/ ???

This is my output:

$ sudo easy_install mercurial
Password:
Searching for mercurial
Reading http://pypi.python.org/simple/mercurial/
Reading http://www.selenic.com/mercurial
Best match: mercurial 1.5.1
Downloading http://mercurial.selenic.com/release/mercurial-1.5.1.tar.gz
Processing mercurial-1.5.1.tar.gz
Running mercurial-1.5.1/setup.py -q bdist_egg --dist-dir /tmp/easy_install-_7RaTq/mercurial-1.5.1/egg-dist-tmp-l7JP3u
mercurial/base85.c:12:20: error: Python.h: No such file or directory
...

Thanks in advance.