All combinations of a list of lists

Question

I m basically looking for a python version of Combination of List lt List lt int gt  gt   Given a list of lists  I need a new list that gives all the possible combinations of items between the lists     1 2 3   4 5 6   7 8 9 10   - gt    1 4 7   1 4 8       3 6 10     The number of lists is unknown  so I need something that works for all cases  Bonus points for elegance

User · Answer

The most elegant solution is to use itertools.product in python 2.6.

If you aren't using Python 2.6, the docs for itertools.product actually show an equivalent function to do the product the "manual" way:

def product(*args, **kwds):
    # product('ABCD', 'xy') --> Ax Ay Bx By Cx Cy Dx Dy
    # product(range(2), repeat=3) --> 000 001 010 011 100 101 110 111
    pools = map(tuple, args) * kwds.get('repeat', 1)
    result = [[]]
    for pool in pools:
        result = [x+[y] for x in result for y in pool]
    for prod in result:
        yield tuple(prod)

User · Answer

listOLists     1 2 3   4 5 6   7 8 9 10   for list in itertools product  listOLists     print list    I hope you find that as elegant as I did when I first encountered it

User · Answer

from itertools import product  list vals      Brand Acronym CBIQ    Brand Acronym  KMEFIC     Brand Country DXB   Brand Country BH    list product  list vals     Output          Brand Acronym CBIQ    Brand Country  DXB            Brand Acronym CBIQ    Brand Country BH            Brand Acronym  KMEFIC    Brand Country  DXB            Brand Acronym  KMEFIC    Brand Country BH

User · Answer

Nothing wrong with straight up recursion for this task  and if you need a version that works with strings  this might fit your needs   combinations       def combine terms  accum       last    len terms     1      n   len terms 0       for i in range n           item   accum   terms 0  i          if last              combinations append item          else              combine terms 1    item     gt  gt  gt  a      ab   cd   ef     12   34   56     gt  gt  gt  combine a       gt  gt  gt  print combinations    ab12    ab34    ab56    cd12    cd34    cd56    ef12    ef34    ef56

User · Answer

One can use base python for this  The code needs a function to flatten lists of lists    def flatten B        function needed for code below      A          for i in B          if type i     list  A extend i          else  A append i      return A   Then one can run    L     1 2 3   4 5 6   7 8 9 10    outlist      templist       for sublist in L      outlist   templist  templist            for sitem in sublist          for oitem in outlist              newitem    oitem              if newitem          newitem    sitem              else  newitem    newitem 0   sitem              templist append flatten newitem    outlist   list filter lambda x  len x   len L   templist      remove some partial lists that also creep in  print outlist    Output      1  4  7    2  4  7    3  4  7     1  5  7    2  5  7    3  5  7     1  6  7    2  6  7    3  6  7     1  4  8    2  4  8    3  4  8     1  5  8    2  5  8    3  5  8     1  6  8    2  6  8    3  6  8     1  4  9    2  4  9    3  4  9     1  5  9    2  5  9    3  5  9     1  6  9    2  6  9    3  6  9     1  4  10    2  4  10    3  4  10     1  5  10    2  5  10    3  5  10     1  6  10    2  6  10    3  6  10

User · Answer

Numpy can do it     gt  gt  gt  import numpy   gt  gt  gt  a     1 2 3   4 5 6   7 8 9 10     gt  gt  gt   list x  for x in numpy array numpy meshgrid  a   T reshape -1 len a       1  4  7    1  5  7    1  6  7

User · Answer

you need itertools product    gt  gt  gt  import itertools  gt  gt  gt  a     1 2 3   4 5 6   7 8 9 10    gt  gt  gt  list itertools product  a     1  4  7    1  4  8    1  4  9    1  4  10    1  5  7    1  5  8    1  5  9    1  5  10    1  6  7    1  6  8    1  6  9    1  6  10    2  4  7    2  4  8    2  4  9    2  4  10    2  5  7    2  5  8    2  5  9    2  5  10    2  6  7    2  6  8    2  6  9    2  6  10    3  4  7    3  4  8    3  4  9    3  4  10    3  5  7    3  5  8    3  5  9    3  5  10    3  6  7    3  6  8    3  6  9    3  6  10

[python] All combinations of a list of lists

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