Converting a list of lists to a single list
MRAB
python at mrabarnett.plus.com
Tue Jul 23 18:52:21 EDT 2013
On 23/07/2013 22:52, steve at divillo.com wrote:
> I think that itertools may be able to do what I want but I have not been able to figure out how.
>
> I want to convert an arbitrary number of lists with an arbitrary number of elements in each list into a single list as follows.
>
> Say I have three lists:
>
> [[A0,A1,A2], [B0,B1,B2] [C0,C1,C2]]
>
> I would like to convert those to a single list that looks like this:
>
> [A0,B0,C0,C1,C2,B1,C0,C1,C2,B2,C0,C1,C2,A1,B0,C0,C1,C2,B1,C0,C1,C2,B2,C0,C1,C2,A2,B0,C0,C1,C2,B1,C0,C1,C2,B2,C0,C1,C2]
>
> An easier way to visualize the pattern I want is as a tree.
>
> A0
> B0
> C0
> C1
> C2
> B1
> C0
> C1
> C2
> B2
> C0
> C1
> C2
> A1
> B0
> C0
> C1
> C2
> B1
> C0
> C1
> C2
> B2
> C0
> C1
> C2
> A2
> B0
> C0
> C1
> C2
> B1
> C0
> C1
> C2
> B2
> C0
> C1
> C2
>
Using recursion:
def tree_list(items):
if len(items) == 1:
return items[0]
sublist = tree_list(items[1 : ])
result = []
for item in items[0]:
result.append(item)
result.extend(sublist)
return result
items = [["A0","A1","A2"], ["B0","B1","B2"], ["C0","C1","C2"]]
print(tree_list(items))
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