"""This module contains some useful functions.
The functions work on the standart library or are not specific to
a certain existing module.
"""
[docs]def unique(iterables):
"""Create an iterable from the iterables that contains each element once.
:return: an iterable over the iterables. Each element of the result
appeared only once in the result. They are oredered by the first
occurrence in the iterables.
"""
included_elements = []
def included(element):
result = element in included_elements
included_elements.append(element)
return result
return [element for elements in iterables for element in elements
if not included(element)]
__all__ = ["unique"]