Looking for better way of making a single list of forwards and reverse directory names for matching with files

Here is the code I'm currently working with.

Input = ['cat','tab','mad dog']
output = [x for x in Input] + [' '.join(x.split(' ')[::-1]) for x in Input if len(x.split())>1]

It works fine and is pretty fast but I don't think it reads particularly well.

Is there anything better that wouldn't sacrifice speed, as that is the most important thing for its use?

Why? its actually for searching directories where the name (one or two words) may have been typed in reverse.

output= ['cat', 'tab', 'mad dog', 'dog mad']

This is the correct result but I'm pretty sure there is a better way of getting there.

Thank you.

as #slothrop commented

Input = ['cat','tab','mad dog']

output = Input + [' '.join(x.split()[::-1]) for x in Input if ' ' in x]

or

Input.append(*[' '.join(x.split()[::-1]) for x in Input if ' ' in x])

or

output = Input + [' '.join(reversed(x.split())) for x in Input if ' ' in x]

#['cat', 'tab', 'mad dog', 'dog mad']

Another approach, flipping the problem round a bit, is to define your collection of target directories as a set of sets of words. A set is inherently unordered, so there's no need to go through every combination. So this would scale up quite well if you have names with more than 2 words.

Then to check whether a directory is of interest to you, turn the directory name into a set of words and see if that's in the target set.

For example:

# 1) Creating the target word sets
input_words = ['cat','tab','mad dog']
target_word_sets = {frozenset(x.split()) for x in input_words}

# 2) Checking a directory name against the target word sets, wherever in the program this is needed
my_dir_names = ['cat', 'mad cat', 'mad dog', 'dog mad']
for dn in my_dir_names:
    is_in_target = set(dn.split()) in target_word_sets
    print(f'{dn}: {is_in_target}')

which prints:

cat: True
mad cat: False
mad dog: True
dog mad: True

Note, when using a set of sets, the inner sets must be hashable, hence the use of frozenset rather than plain old set.