# Cartesian Product of two lists (itertools)

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## Cartesian Product of two lists (itertools)

 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: 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] Thorsten -- http://mail.python.org/mailman/listinfo/python-list
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## Re: Cartesian Product of two lists (itertools)

 On Jan 25, 3:12�pm, Thorsten Kampe <[hidden email]> 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: > > 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] > > Thorsten Will this work for you? >>> list4 = [(i,) for i in list3] >>> list4 [(7,), (8,)] >>> a = list(itertools.product(itertools.product(list1, list2), list4)) >>> a [((1, 4), (7,)), ((1, 4), (8,)), ((1, 5), (7,)), ((1, 5), (8,)), ((2, 4), (7,)), ((2, 4), (8,)), ((2, 5), (7,)), ((2, 5), (8,))] >>> def flatten(listOfLists):     return tuple(itertools.chain.from_iterable(listOfLists)) >>> list5 = [flatten(i) for i in a] >>> list5 [(1, 4, 7), (1, 4, 8), (1, 5, 7), (1, 5, 8), (2, 4, 7), (2, 4, 8), (2, 5, 7), (2, 5, 8)] >>> -- http://mail.python.org/mailman/listinfo/python-list
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## Re: Cartesian Product of two lists (itertools)

 In reply to this post by Thorsten Kampe 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)) -- http://mail.python.org/mailman/listinfo/python-list