Possible to append multiple lists at once? (Python)

Question

I have a bunch of lists I want to append to a single list that is sort of the \"main\" list in a program I\'m trying to write. Is there a way to do this in one line of code

Answer 1

You can use sum function with start value (empty list) indicated:

a = sum([x, y, z], [])

This is especially more suitable if you want to append an arbitrary number of lists.

Answer 2

Extending my comment

In [1]: x = [1, 2, 3]
In [2]: y = [4, 5, 6]
In [3]: z = [7, 8, 9]
In [4]: from itertools import chain
In [5]: print list(chain(x,y,z))
[1, 2, 3, 4, 5, 6, 7, 8, 9]

Answer 3

To exactly replicate the effect of append, try the following function, simple and effective:

a=[]
def concats (lists):
    for i in lists:
        a==a.append(i)


concats ([x,y,z])
print(a)

Answer 4

x.extend(y+z)

should do what you want

or

x += y+z

or even

x = x+y+z

Answer 5

equivalent to above answer, but sufficiently different to be worth a mention:

my_map = {
   'foo': ['a', 1, 2],
   'bar': ['b', '2', 'c'],
   'baz': ['d', 'e', 'f'],
} 
list(itertools.chain(*my_map.values()))
['d', 'e', 'f', 'a', 1, 2, 'b', '2', 'c']

in the above expression, * is important for groking result as args to chain, this is same as prior chain(x,y,z). Also, note the result is hash-ordered.

Answer 6

In one line , it can be done in following ways

x.extend(y+z)

or

x=x+y+z