functions.py

# http://www.matusiak.eu/numerodix/blog/index.php/2010/03/08/python-patterns-for-graph-traversal/
# Shows that python function parameter defaults can in fact change.
# A short example:

def a(x=[]):
    x += 'b'
    print x

print a.func_defaults
# ([],)

a()
# ['b']

print a.func_defaults
# (['b'],)

a()
# ['b', 'b']

print a.func_defaults
# (['b', 'b'],)