Remove extra empty strings?

Question

Let's say I have a Python list of strings like so:

x = ["", "", "test", "", "", "not empty", "", "yes", ""]

How can I remove:

1. all leading empty strings
2. all trailing empty strings
3. all 'repeated' empty strings
   (ie reduce all internal sequences of empty space values to a single value)

['test', '', 'not empty', '', 'yes']

Answer 1

content = list(x.next() for i, x in it.groupby(content))
b_l_rgx = r"^(\s+)?$"
if re.match(b_l_rgx, content[0]):
    del content[0]
if len(content) > 0 and re.match(b_l_rgx, content[-1]):
    del content[-1]

Answer 2

Here's the solution I came up with using dropwhile and groupby

from itertools import groupby, dropwhile

def spaces(iterable):
    it = dropwhile(lambda x: not x, iterable)
    grby = groupby(it, key=bool)
    try:
        k, g = next(grby)
    except StopIteration:
        return
    yield from g
    for k, g in grby:
        if k:
            yield ''
            yield from g

x = ["", "", "test", "", "", "not empty", "", "yes", ""]
print(list(spaces(x)))
# ['test', '', 'not empty', '', 'yes']