Thorsten Kampe wrote:
Hi,
is there a way to make itertools.product generate triples instead of
pairs from two lists?
For example:
list1 = [1, 2]; list2 = [4, 5]; list3 = [7, 8]
from itertools import product
list(product(list1, list2, list3))
[(1, 4, 7), (1, 4, 8), (1, 5, 7), (1, 5, 8), (2, 4, 7), (2, 4, 8), (2,
5, 7), (2, 5, 8)]
so far so good... Now...
list(product(product(list1, list2), list3))
[((1, 4), 7), ((1, 4), 8), ((1, 5), 7), ((1, 5), 8), ((2, 4), 7), ((2,
4), 8), ((2, 5), 7), ((2, 5), 8)]
Oops, pairs of pairs instead triples. Not what I wanted.
What's the best way to pre-process the arguments to "itertools.product"
or to post-process the result of "itertools.product" to get what I
want?!
I have an older utility which I would like to replace with
itertools.product. The old one uses a rather clumsy way to indicate that
a triple was wanted:
A pair of function, cart_pair, cart_trip, would have been better.
Or auto recognition of the number of sequences passed in.
def cartes(seq0, seq1, modus = 'pair'):
""" return the Cartesian Product of two sequences """
if modus == 'pair':
return [[item0, item1] for item0 in seq0 for item1 in seq1]
elif modus == 'triple':
return [item0 + [item1] for item0 in seq0 for item1 in seq1]
The second branch only produces a triple if seq0 is a sequence of pairs.
This must be called with something like
res = cartes(cartes(list1,list2),list3,'triple')
Just replace that with your first only-once itertools call
list(product(list1, list2, list3))
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