"""Provide an iterator for automatically nesting multiple sequences.
The "nest" generator function in this module is provided to make writing
nested loops easier to accomplish. Instead of writing a for loop at each
level, one may call "nest" with each sequence as an argument and receive
items from the sequences correctly yielded back to the caller. A test is
included at the bottom of this module to demonstrate how to use the code."""
__author__ = 'Stephen "Zero" Chappell <Noctis.Skytower@gmail.com>'
__date__ = '17 February 2012'
__version__ = 1, 0, 0
################################################################################
def nest(*iterables):
"Iterate over the iterables as if they were nested in loops."
return _nest(list(map(tuple, reversed(iterables))))
def _nest(stack):
"Build recursive loops and iterate over tuples on the stack."
top = stack.pop()
if stack:
for v1 in top:
for v2 in _nest(stack):
yield (v1,) + v2
else:
for value in top:
yield (value,)
stack.append(top)
################################################################################
def test():
"Check the nest generator function for correct yield values."
subject = 'I He She It They Adam Eve Cain Abel Zacharias'.split()
verb = 'ate bought caught dangled elected fought got hit'.split()
complement = 'an elephant,a cow,the boot,my gun,its head'.split(',')
for sentence in nest(subject, verb, complement):
print('{} {} {}.'.format(*sentence))
if __name__ == '__main__':
test()
