Experimenting and messing with Python (v2.7) source code, inspired by two blog posts, Replacing import with accio: A Dive into Bootstrapping and Python's Grammar and Python internals: adding a new statement to Python.

First step is to clone and install. Details as to why we need this intermediary version of Python can be read in this article

git clone git@github.com:dr4ke616/custom_python.git
cd intermediary_python/
./configure --with-pydebug
make clean && make -s -j2
cd bin/
export PATH=`pwd`:$PATH

Now we go to the my_python directory and install the new version

cd ../../my_python
./configure --with-pydebug
make clean && make -s -j2
cd bin/
export PATH=`pwd`:$PATH
cd ../../

We can test now with:

python test_custom_python.py

>>> print "hello"
  File "<stdin>", line 1
    print 'hello'
                ^
SyntaxError: invalid syntax

>>> shout 'hello'
hello

Checkout test_custom_python.py for some more examples