Build and install python and mercurial from scratch on a system

wget http://www.python.org/ftp/python/2.5.4/Python-2.5.4.tgz
wget http://www.selenic.com/mercurial/release/mercurial-1.2.1.tar.gz
tar zxvf mercurial-1.2.1.tar.gz
tar zxvf Python-2.5.4.tgz

Configure and build Python using /opt - you could use /usr/local or similar but I preferred to keep it out of my $PATH:

cd Python-2.5.4
./configure --prefix=/opt
make
su -c "make install"

Test Python installed properly:

/opt/bin/python
Python 2.5.4 (r254:67916, Mar 25 2009, 12:16:36)
[GCC 3.2.3 20030502 (Red Hat Linux 3.2.3-56)] on linux2
Type "help", "copyright", "credits" or "license" for more information.

Build Mercurial, using your Python 2.5:

cd ../mercurial-1.2.1
su -c "make install PYTHON=/opt/bin/python PREFIX=/opt"

Test Mercurial installed properly:

/opt/bin/hg --version
Mercurial Distributed SCM (version 1.2.1)
Copyright (C) 2005-2009 Matt Mackall and others

You may wish to symlink hg from somewhere in your $PATH:

su -c "ln -s /opt/bin/hg /usr/local/bin/hg"

Obviously you'll need a C compiler and associated development tools installed. You may find that the Python configure command complains of missing libraries, such as zlib-devel which can be installed via yum if required

Source: http://blog.friedland.id.au/2009/03/installing-mercurial-on-rhelcentos-3.html