I am trying to concatenate two lists, one with just one element, by doing this:
print([6].append([1,1,0,0,0]))
However, Python returns None. What am I doing wrong?
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4 Answers
Use the + operator
>>> [6] + [1,1,0,0,0]
[6, 1, 1, 0, 0, 0]
What you were attempting to do, is append a list onto another list, which would result in
>>> [6].append([1,1,0,0,0])
[6, [1,1,0,0,0]]
Why you are seeing None returned, is because .append is destructive, modifying the original list, and returning None. It does not return the list that you're appending to. So your list is being modified, but you're printing the output of the function .append.
Comments
For list concatenation you have two options:
newlist = list1 + list2
list1.extend(list2)
use a list first (unless you really do not want to use your data in future )
>>> a=[6]
>>> a.append([1,1,0,0,0])
>>> a
[6, [1, 1, 0, 0, 0]]
another way is to use extend() instead of append()
>>> a=[6]
>>> a.extend([1,1,0,0,0])
>>> a
[6, 1, 1, 0, 0, 0]
1 Comment
steabert
I like the mention of extend as alternative to summing, but I downvoted this answer because the result of extend is not the same as append, although in your answer you pretend like it is a different way to get the same result...
l1 = [6]
l2 = [1, 1, 0, 0, 0]
l1.extend(l2)
print l1
[6, 1, 1, 0, 0, 0]
