python - List with duplicated values and suffix

Question

I have a list, a:

a = ['a','b','c']

and need to duplicate some values with the suffix _ind added this way (order is important):

['a', 'a_ind', 'b', 'b_ind', 'c', 'c_ind']

I tried:

b = [[x, x + '_ind'] for x in a]
c = [item for sublist in b for item in sublist]
print (c)
['a', 'a_ind', 'b', 'b_ind', 'c', 'c_ind']

Is there some better, more pythonic solution?

Answer 1

You could make it a generator:

def mygen(lst):
    for item in lst:
        yield item
        yield item + '_ind'

>>> a = ['a','b','c']
>>> list(mygen(a))
['a', 'a_ind', 'b', 'b_ind', 'c', 'c_ind']

You could also do it with itertools.product, itertools.starmap or itertools.chain or nested comprehensions but in most cases I would prefer a simple to understand, custom generator-function.

---

With python3.3, you can also use yield from—generator delegation—to make this elegant solution just a bit more concise:

def mygen(lst):
    for item in lst:
        yield from (item, item + '_ind')