Hard time trying to figure out the difference between two strings

[carecavoador]

Greetings, fellow pythonistas.

Considering I have the following filenames:

filenames = [
    "BCY0649_PURANATTA_120X90MM__ Cyan.tif"
    "BCY0649_PURANATTA_120X90MM__ Black.tif"
    "BCY0649_PURANATTA_120X90MM__ Magenta.tif"
    "BCY0649_PURANATTA_120X90MM__ PANTONE 357 C.tif"
    "BCY0649_PURANATTA_120X90MM__ PANTONE 465 C.tif"
    "BCY0649_PURANATTA_120X90MM__ Yellow.tif"
]

I need to get the last part of the filenames (Cyan, Magenta, PANTONE 357 C etc). In this case in particular, I can do it easily spliting the string on the double underscores "__".

But, this will not always be the case. I'm frying my brains trying to make this work, but couldn't figure it out.

What I have done so far: tryied to look for matching characters on two filenames and guess what is the prefix. But this will fail if I have lets say only two PANTONE colors, as they will be included in the prefix.

def get_filename_prefix(first: str, second: str) -> str:
    prefix = []
    first = first.split()
    second = second.split()
    for one in first:
        for another in second:
            if one == another:
                prefix.append(one)
    return " ".join(prefix)

Any better ideas?