groupby(iterable[, keyfunc]) -->
sub-iterators grouped by value of keyfunc(v)
Beispiel:
>>> from itertools import groupby
>>> terms = [("country", "France"), ("city", "Paris"), ("city", "Berlin"), ("river", "Rhein"), ("country", "Italy")]
>>> for category, elements in groupby(terms, lambda x: x[0]):
... print(category, list(elements))
...
country [('country', 'France')]
city [('city', 'Paris'), ('city', 'Berlin')]
river [('river', 'Rhein')]
country [('country', 'Italy')]