I want two lists inside one list:
x = [1,2]
y = [3,4]
I need them to turn out like:
z = [[1,2][3,4]]
But I have no idea how to do that. Thanks so much for your consideration and help.
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1Possible duplicate of What is the fastest way to merge two lists in python?Aida Paul– Aida Paul2015-11-23 18:23:42 +00:00Commented Nov 23, 2015 at 18:23
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2@TymoteuszPaul If I'm not mistaken, this question is slightly different from the question you've posted above.ssundarraj– ssundarraj2015-11-23 18:24:37 +00:00Commented Nov 23, 2015 at 18:24
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4 Answers
Make a new list which contains the first two lists.
z = [x, y]
This will make each element of z a reference to the original list. If you don't want that to happen you can do the following.
from copy import copy
z = [copy(x), copy(y)]
print z
2 Comments
Padraic Cunningham
you just created references to x and y, any changes to either would mean the list of lists would change
ssundarraj
@PadraicCunningham Thanks for pointing that out. I overlooked it. Edited my answer.
If you don't want references to the original list objects:
z = [x[:], y[:]]
3 Comments
ssundarraj
Although this isn't explicit and readable, this approach is really interesting!
MattDMo
@ssundarraj it's doing the same thing as your answer, except in a more succinct manner. In my mind this is just as explicit and readable as yours, without the extra import and lines of code.
ssundarraj
@MattDMo Agreed! It's very succinct. It's less explicit though. That's all I meant to convey. I really like this approach. I will probably be using it myself.
This will work:
>>> x = [1, 2]
>>> y = [3, 4]
>>> z = [x, y]
>>> print("z = ", z)
z = [[1, 2], [3, 4]]
1 Comment
MattDMo
except that
z contains references to x and y, not their actual values. If x or y are changed somewhere down the line, z will change as well, which likely isn't the intention of the programmer. This causes hard-to-find bugs.x = [ 1, 2 ]
y = [ 2, 3 ]
z =[]
z.append(x)
z.append(y)
print z
output:
[[1, 2], [2, 3]]
