docs/examples/lib/example-demo.py

"""A simple interactive demo to illustrate the use of IPython's Demo class.

Any python script can be run as a demo, but that does little more than showing
it on-screen, syntax-highlighted in one shot.  If you add a little simple
markup, you can stop at specified intervals and return to the ipython prompt,
resuming execution later.
"""
from __future__ import print_function

print('Hello, welcome to an interactive IPython demo.')
print('Executing this block should require confirmation before proceeding,')
print('unless auto_all has been set to true in the demo object')

# The mark below defines a block boundary, which is a point where IPython will
# stop execution and return to the interactive prompt.
# Note that in actual interactive execution, 
# <demo> --- stop ---

x = 1
y = 2

# <demo> --- stop ---

# the mark below makes this block as silent
# <demo> silent

print('This is a silent block, which gets executed but not printed.')

# <demo> --- stop ---
# <demo> auto
print('This is an automatic block.')
print('It is executed without asking for confirmation, but printed.')
z = x+y

print('z=',x)

# <demo> --- stop ---
# This is just another normal block.
print('z is now:', z)

print('bye!')