How to extend list comprehension with values outside the set builder?

Question

I am basically looking for a one-liner to create a list using the python list comprehension feature, but also to add some extra value/values that do not fit the pattern. So for example I would like to get a list with the following values [1, 2, 3, 4, 5, 50]. I have tried the following:

a = [i for i in range(6), 50] # [[0, 1, 2, 3, 4, 5], 50]
b = [i for i in range(6)].append(50) # None
c = [i for i in range(6)].extend([50]) # None

Besides the actual answer, explanations about why none of my lists return the desired output are highly appreciated.

Answer 1

Simply concatenate lists using +:

>>> d = [i for i in range(6)] + [50]
>>> d
[0, 1, 2, 3, 4, 5, 50]

Answer 2

Just wanted to point out, that is not the only place you can do that addition, and in other places it makes more sense:

In [1]: d = [i for i in range(6)] + [50]

In [2]: print d
[0, 1, 2, 3, 4, 5, 50]

In [3]: d = [i for i in range(6) + [50]]

In [4]: print d
[0, 1, 2, 3, 4, 5, 50]

In [5]: d = [i*2 for i in range(6) + [50]]

In [6]: print d
[0, 2, 4, 6, 8, 10, 100]

In that case, it's a lot more useful to have a one-liner.

That won't work in python 3+ though, because xrange is not a list; it's a generator. The more general form uses itertools.chain:

In [7]: d = [i*2 for i in xrange(6) + [50]]
---------------------------------------------------------------------------
TypeError                                 Traceback (most recent call last)
<ipython-input-7-7c5dfed6c9b9> in <module>()
----> 1 d = [i*2 for i in xrange(6) + [50]]

TypeError: unsupported operand type(s) for +: 'xrange' and 'list'

In [8]: from itertools import chain

In [9]: d = [i*2 for i in chain(xrange(6),[50])]

In [10]: print d
[0, 2, 4, 6, 8, 10, 100]

Answer 3

The append() and extend() functions return None since they modify the list in place, so that should explain that. If you wanted that to work you would need to do:

b = [i for i in range(6)]
b.append(50)

I don't know of any "pythonic" way to do it in one line aside from a. Or as pointed out in the comments:

d = [i for i in range(6)] + AnotherListWithExtraCharacters

Answer 4

You can use add operator:

print [i for i in range(6)] + [50]
>>> [0, 1, 2, 3, 4, 5, 50]