How do I parse the string?

[menator01]

Another way

astring = 'FTP://21.105.28.15/abc/test1.txt'
astring2 = 'FTP://21.105.28.15/abc/def/test1.txt'

def remover(astring):
    astring = astring.split('/')
    for index, item in enumerate(astring):
        if item == '':
            astring.remove(item)
        elif index in (0, 1):
            astring.remove(item)
    return '/'.join(astring)

print(remover(astring))
print(remover(astring2))

output

Output:
/abc/test1.txt
/abc/def/test1.txt

little adjustment can remove the file at the end as well