Question

Ref:
python decompose a list
Flattening a shallow list in Python

While the above mentioned solutions are helpful, my problem is slightly different, and I was wondering if there is a pythonic way to solve it.

a = [['a-3','b-3'],'r',['j']]

What I would like, is a clean way of making ‘a’ equal the following:

a = ['a-3','b-3','r','j']

I am stuck using python 2.4 so a pythonic solution that’s 2.4 compatible would be great, but I would still find 2.7+ examples interesting as well.

The main problem is that there are non-iterable elements, otherwise the sum(lst,[]) works quite well, as does the chain method for 2.7+

Answer 1

Pythonic solution can mean many thing. With readability counts (PEP 20) in mind, this is my contribution to the thread:

def dec(input_, output_):
    if type(input_) is list:
        for subitem in input_:
            dec(subitem, output_)
    else:
        output_.append(input_)

Example:

input_ = [['a-3','b-3', ['x','hello', ['3','b']]],'r',['j']]
output_ = ['a-3', 'b-3', 'x', 'hello', '3', 'b', 'r', 'j']