Here I'm trying to merge this two lists, making one whit all items.
n = [[1, 2, 3], [4, 5, 6, 7, 8, 9]]
def flatten(n):
s=[]
for x in n:
s.append(x)
return s
print flatten(n)
I'm trying to have as a result
[1,2,3,4,5,6,7,8,9]
but I'm getting
[[1, 2, 3], [4, 5, 6, 7, 8, 9]]
I dont understand why, I think I'm clearly assigning each value to the list 's' in the for loop.
You're appending to the list. Each sublist is appended to the new list as its own item, exactly the way it was originally. You want to extend the list instead:
s.extend(x)
Use extend, instead of append
n = [[1, 2, 3], [4, 5, 6, 7, 8, 9]]
def flatten(n):
s=[]
for x in n:
s.extend(x)
return s
print flatten(n)
Best of luck.
You should be using list.extend, append is appending each sublist not adding just the contents. x is each sublist so just appending the sublist is obviously going to give you a list of lists again.
You can also use itertools.chain to flatten the list:
n = [[1, 2, 3], [4, 5, 6, 7, 8, 9]]
print(list(chain.from_iterable(n)))
Or use a list comp:
n = [[1, 2, 3], [4, 5, 6, 7, 8, 9]]
print([ele for sub in n for ele in sub])
