Convert list of tuples to list?

Question

How do I convert

[(1,), (2,), (3,)]

to

[1, 2, 3]

Answer 1

You can also unpack the tuple in the list comprehension:

e = [(1,), (2,), (3,)]
[i for (i,) in e]

will still give:

[1, 2, 3]

Answer 2

You can also use sum function as follows:

e = [(1,), (2,), (3,)] 
e_list = list(sum(e, ()))

And it also works with list of lists to convert it into a single list, but you will need to use it as follow:

e = [[1, 2], [3, 4], [5, 6]]
e_list = list(sum(e, []))

This will give you [1, 2, 3, 4, 5, 6]

Answer 3

>>> a = [(1,), (2,), (3,)]
>>> b = map(lambda x: x[0], a)
>>> b
[1, 2, 3]

With python3, you have to put the list(..) function to the output of map(..), i.e.

b = list(map(lambda x: x[0], a))

This is the best solution in one line using python built-in functions.

Answer 4

There's always a way to extract a list from another list by ...for...in.... In this case it would be:

[i[0] for i in e]

Answer 5

>>> a = [(1,), (2,), (3,)]
>>> zip(*a)[0]
(1, 2, 3)

For a list:

>>> list(zip(*a)[0])
[1, 2, 3]

Answer 6

Using operator or sum

>>> from functools import reduce ### If python 3
>>> import operator
>>> a = [(1,), (2,), (3,)]
>>> list(reduce(operator.concat, a))
[1, 2, 3]

(OR)

>>> list(sum(a,()))
[1, 2, 3]
>>> 

If in python > 3 please do the import of reduce from functools like from functools import reduce

https://docs.python.org/3/library/functools.html#functools.reduce