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Combinations of multiple lists


How do I check if a list is empty?Finding the index of an item given a list containing it in PythonDifference between append vs. extend list methods in PythonHow to return multiple values from a function?How to make a flat list out of list of lists?How do I concatenate two lists in Python?How to clone or copy a list?How do I list all files of a directory?How to read a file line-by-line into a list?Catch multiple exceptions in one line (except block)






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6















Suppose I have three lists: 



list1 --> [a, b, c, d, e, f, g, h]
list2 --> [i, j, k]
list3 --> [l, m, n, o, p]


I wish to generate all combinations where I take five elements from list1, two elements from list2 and three elements from list3.



eg. 



a, b, c, d, e, i, j, l, m, n 
a, b, c, d, e, i, j, l, m, o
etc.


I tried to use itertools.combinations. 



l1_combinations = itertools.combinations(list1, 5)
l2_combinations = itertools.combinations(list2, 2)
l3_combinations = itertools.combinations(list3, 3)
for l1_iterator in list(l1_combinations):
 for l2_iterator in list(l2_combinations): #added a missing )
 for l3_iterator in list(l3_combinations):
 sample = l1_iterator + l2_iterator + l3_iterator
 print(sample)


But I am getting output with iterations happening only on list3. In all the output, only first five elements from list1 and first two elements from list2 are present. Combinations with other elements from those two lists aren't present.



Can someone help me here and also explain what exactly did i miss ?






python







share|improve this question
























  • Well I'm sure the missing ) in for l2_iterator in list(l2_combinations: doesn't help...

    – Reedinationer
    1 hour ago

















6















Suppose I have three lists: 



list1 --> [a, b, c, d, e, f, g, h]
list2 --> [i, j, k]
list3 --> [l, m, n, o, p]


I wish to generate all combinations where I take five elements from list1, two elements from list2 and three elements from list3.



eg. 



a, b, c, d, e, i, j, l, m, n 
a, b, c, d, e, i, j, l, m, o
etc.


I tried to use itertools.combinations. 



l1_combinations = itertools.combinations(list1, 5)
l2_combinations = itertools.combinations(list2, 2)
l3_combinations = itertools.combinations(list3, 3)
for l1_iterator in list(l1_combinations):
 for l2_iterator in list(l2_combinations): #added a missing )
 for l3_iterator in list(l3_combinations):
 sample = l1_iterator + l2_iterator + l3_iterator
 print(sample)


But I am getting output with iterations happening only on list3. In all the output, only first five elements from list1 and first two elements from list2 are present. Combinations with other elements from those two lists aren't present.



Can someone help me here and also explain what exactly did i miss ?






python







share|improve this question
























  • Well I'm sure the missing ) in for l2_iterator in list(l2_combinations: doesn't help...

    – Reedinationer
    1 hour ago













6












6








6








Suppose I have three lists: 



list1 --> [a, b, c, d, e, f, g, h]
list2 --> [i, j, k]
list3 --> [l, m, n, o, p]


I wish to generate all combinations where I take five elements from list1, two elements from list2 and three elements from list3.



eg. 



a, b, c, d, e, i, j, l, m, n 
a, b, c, d, e, i, j, l, m, o
etc.


I tried to use itertools.combinations. 



l1_combinations = itertools.combinations(list1, 5)
l2_combinations = itertools.combinations(list2, 2)
l3_combinations = itertools.combinations(list3, 3)
for l1_iterator in list(l1_combinations):
 for l2_iterator in list(l2_combinations): #added a missing )
 for l3_iterator in list(l3_combinations):
 sample = l1_iterator + l2_iterator + l3_iterator
 print(sample)


But I am getting output with iterations happening only on list3. In all the output, only first five elements from list1 and first two elements from list2 are present. Combinations with other elements from those two lists aren't present.



Can someone help me here and also explain what exactly did i miss ?






python







share|improve this question
















Suppose I have three lists: 



list1 --> [a, b, c, d, e, f, g, h]
list2 --> [i, j, k]
list3 --> [l, m, n, o, p]


I wish to generate all combinations where I take five elements from list1, two elements from list2 and three elements from list3.



eg. 



a, b, c, d, e, i, j, l, m, n 
a, b, c, d, e, i, j, l, m, o
etc.


I tried to use itertools.combinations. 



l1_combinations = itertools.combinations(list1, 5)
l2_combinations = itertools.combinations(list2, 2)
l3_combinations = itertools.combinations(list3, 3)
for l1_iterator in list(l1_combinations):
 for l2_iterator in list(l2_combinations): #added a missing )
 for l3_iterator in list(l3_combinations):
 sample = l1_iterator + l2_iterator + l3_iterator
 print(sample)


But I am getting output with iterations happening only on list3. In all the output, only first five elements from list1 and first two elements from list2 are present. Combinations with other elements from those two lists aren't present.



Can someone help me here and also explain what exactly did i miss ?






python




python






share|improve this question















share|improve this question













share|improve this question




share|improve this question








edited 1 hour ago









amchugh89

595621




595621










asked 1 hour ago









Arun AranganathanArun Aranganathan

425




425












  • Well I'm sure the missing ) in for l2_iterator in list(l2_combinations: doesn't help...

    – Reedinationer
    1 hour ago

















  • Well I'm sure the missing ) in for l2_iterator in list(l2_combinations: doesn't help...

    – Reedinationer
    1 hour ago
















Well I'm sure the missing ) in for l2_iterator in list(l2_combinations: doesn't help...

– Reedinationer
1 hour ago





Well I'm sure the missing ) in for l2_iterator in list(l2_combinations: doesn't help...

– Reedinationer
1 hour ago












2 Answers
2






active

oldest

votes


















7














As an alternative to regenerating the list of combinations, compute the product of the combinations up front; this also saves you from nesting for loops.



from itertools import combinations, product


list1 = list("abcdefgh")
list2 = list("ijk")
list3 = list("lmnop")

l1 = combinations(list1, 5)
l2 = combinations(list2, 2)
l3 = combinations(list3, 3)
for c1, c2, c3 in product(l1, l2, l3):
 sample = c1 + c2 + c3
 print(sample)





share|improve this answer






























    6














    Don't iterate over the same iterator multiple times, after the first time it's exhausted. Iterate over a fresh iterator each time:



    for l1_iterator in itertools.combinations(list1, 5):
     for l2_iterator in itertools.combinations(list2, 2):
     for l3_iterator in itertools.combinations(list3, 3):
     sample = l1_iterator + l2_iterator + l3_iterator
     print(sample)


    Or make lists of each one in advance to avoid recomputation:



    l1_combinations = list(itertools.combinations(list1, 5))
    l2_combinations = list(itertools.combinations(list2, 2))
    l3_combinations = list(itertools.combinations(list3, 3))
    for l1_iterator in l1_combinations:
     for l2_iterator in l2_combinations:
     for l3_iterator in l3_combinations:
     sample = l1_iterator + l2_iterator + l3_iterator
     print(sample)





    share|improve this answer

























    • What would be a solution to not regenerate the combinations every time?

      – ritlew
      1 hour ago






    • 2





      @ritlew see edit.

      – Alex Hall
      1 hour ago











    Your Answer






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    2 Answers
    2






    active

    oldest

    votes








    2 Answers
    2






    active

    oldest

    votes









    active

    oldest

    votes






    active

    oldest

    votes









    7














    As an alternative to regenerating the list of combinations, compute the product of the combinations up front; this also saves you from nesting for loops.



    from itertools import combinations, product


    list1 = list("abcdefgh")
    list2 = list("ijk")
    list3 = list("lmnop")

    l1 = combinations(list1, 5)
    l2 = combinations(list2, 2)
    l3 = combinations(list3, 3)
    for c1, c2, c3 in product(l1, l2, l3):
     sample = c1 + c2 + c3
     print(sample)





    share|improve this answer



























      7














      As an alternative to regenerating the list of combinations, compute the product of the combinations up front; this also saves you from nesting for loops.



      from itertools import combinations, product


      list1 = list("abcdefgh")
      list2 = list("ijk")
      list3 = list("lmnop")

      l1 = combinations(list1, 5)
      l2 = combinations(list2, 2)
      l3 = combinations(list3, 3)
      for c1, c2, c3 in product(l1, l2, l3):
       sample = c1 + c2 + c3
       print(sample)





      share|improve this answer

























        7












        7








        7







        As an alternative to regenerating the list of combinations, compute the product of the combinations up front; this also saves you from nesting for loops.



        from itertools import combinations, product


        list1 = list("abcdefgh")
        list2 = list("ijk")
        list3 = list("lmnop")

        l1 = combinations(list1, 5)
        l2 = combinations(list2, 2)
        l3 = combinations(list3, 3)
        for c1, c2, c3 in product(l1, l2, l3):
         sample = c1 + c2 + c3
         print(sample)





        share|improve this answer













        As an alternative to regenerating the list of combinations, compute the product of the combinations up front; this also saves you from nesting for loops.



        from itertools import combinations, product


        list1 = list("abcdefgh")
        list2 = list("ijk")
        list3 = list("lmnop")

        l1 = combinations(list1, 5)
        l2 = combinations(list2, 2)
        l3 = combinations(list3, 3)
        for c1, c2, c3 in product(l1, l2, l3):
         sample = c1 + c2 + c3
         print(sample)






        share|improve this answer












        share|improve this answer



        share|improve this answer










        answered 1 hour ago









        chepnerchepner

        260k34250343




        260k34250343























            6














            Don't iterate over the same iterator multiple times, after the first time it's exhausted. Iterate over a fresh iterator each time:



            for l1_iterator in itertools.combinations(list1, 5):
             for l2_iterator in itertools.combinations(list2, 2):
             for l3_iterator in itertools.combinations(list3, 3):
             sample = l1_iterator + l2_iterator + l3_iterator
             print(sample)


            Or make lists of each one in advance to avoid recomputation:



            l1_combinations = list(itertools.combinations(list1, 5))
            l2_combinations = list(itertools.combinations(list2, 2))
            l3_combinations = list(itertools.combinations(list3, 3))
            for l1_iterator in l1_combinations:
             for l2_iterator in l2_combinations:
             for l3_iterator in l3_combinations:
             sample = l1_iterator + l2_iterator + l3_iterator
             print(sample)





            share|improve this answer

























            • What would be a solution to not regenerate the combinations every time?

              – ritlew
              1 hour ago






            • 2





              @ritlew see edit.

              – Alex Hall
              1 hour ago















            6














            Don't iterate over the same iterator multiple times, after the first time it's exhausted. Iterate over a fresh iterator each time:



            for l1_iterator in itertools.combinations(list1, 5):
             for l2_iterator in itertools.combinations(list2, 2):
             for l3_iterator in itertools.combinations(list3, 3):
             sample = l1_iterator + l2_iterator + l3_iterator
             print(sample)


            Or make lists of each one in advance to avoid recomputation:



            l1_combinations = list(itertools.combinations(list1, 5))
            l2_combinations = list(itertools.combinations(list2, 2))
            l3_combinations = list(itertools.combinations(list3, 3))
            for l1_iterator in l1_combinations:
             for l2_iterator in l2_combinations:
             for l3_iterator in l3_combinations:
             sample = l1_iterator + l2_iterator + l3_iterator
             print(sample)





            share|improve this answer

























            • What would be a solution to not regenerate the combinations every time?

              – ritlew
              1 hour ago






            • 2





              @ritlew see edit.

              – Alex Hall
              1 hour ago













            6












            6








            6







            Don't iterate over the same iterator multiple times, after the first time it's exhausted. Iterate over a fresh iterator each time:



            for l1_iterator in itertools.combinations(list1, 5):
             for l2_iterator in itertools.combinations(list2, 2):
             for l3_iterator in itertools.combinations(list3, 3):
             sample = l1_iterator + l2_iterator + l3_iterator
             print(sample)


            Or make lists of each one in advance to avoid recomputation:



            l1_combinations = list(itertools.combinations(list1, 5))
            l2_combinations = list(itertools.combinations(list2, 2))
            l3_combinations = list(itertools.combinations(list3, 3))
            for l1_iterator in l1_combinations:
             for l2_iterator in l2_combinations:
             for l3_iterator in l3_combinations:
             sample = l1_iterator + l2_iterator + l3_iterator
             print(sample)





            share|improve this answer















            Don't iterate over the same iterator multiple times, after the first time it's exhausted. Iterate over a fresh iterator each time:



            for l1_iterator in itertools.combinations(list1, 5):
             for l2_iterator in itertools.combinations(list2, 2):
             for l3_iterator in itertools.combinations(list3, 3):
             sample = l1_iterator + l2_iterator + l3_iterator
             print(sample)


            Or make lists of each one in advance to avoid recomputation:



            l1_combinations = list(itertools.combinations(list1, 5))
            l2_combinations = list(itertools.combinations(list2, 2))
            l3_combinations = list(itertools.combinations(list3, 3))
            for l1_iterator in l1_combinations:
             for l2_iterator in l2_combinations:
             for l3_iterator in l3_combinations:
             sample = l1_iterator + l2_iterator + l3_iterator
             print(sample)






            share|improve this answer














            share|improve this answer



            share|improve this answer








            edited 1 hour ago

























            answered 1 hour ago









            Alex HallAlex Hall

            23k32053




            23k32053












            • What would be a solution to not regenerate the combinations every time?

              – ritlew
              1 hour ago






            • 2





              @ritlew see edit.

              – Alex Hall
              1 hour ago

















            • What would be a solution to not regenerate the combinations every time?

              – ritlew
              1 hour ago






            • 2





              @ritlew see edit.

              – Alex Hall
              1 hour ago
















            What would be a solution to not regenerate the combinations every time?

            – ritlew
            1 hour ago





            What would be a solution to not regenerate the combinations every time?

            – ritlew
            1 hour ago




            2




            2





            @ritlew see edit.

            – Alex Hall
            1 hour ago





            @ritlew see edit.

            – Alex Hall
            1 hour ago

















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