import re
regex = r"(((?<=### http:\/\/archive\.semantyk\.com\/).*)|(?<=archive:)([^\s]+))"
test_str = ("### http://a...content-available-to-author-only...k.com/ test\n"
"archive:test")
subst = "186e4707_afc8_4d0d_8c56_26e595eba8f0"
result = re.sub(regex, subst, test_str, 0)
print (result)
aW1wb3J0IHJlCgpyZWdleCA9IHIiKCgoPzw9IyMjIGh0dHA6XC9cL2FyY2hpdmVcLnNlbWFudHlrXC5jb21cLykuKil8KD88PWFyY2hpdmU6KShbXlxzXSspKSIKCnRlc3Rfc3RyID0gKCIjIyMgaHR0cDovL2EuLi5jb250ZW50LWF2YWlsYWJsZS10by1hdXRob3Itb25seS4uLmsuY29tLyB0ZXN0XG4iCgkiYXJjaGl2ZTp0ZXN0IikKCnN1YnN0ID0gIjE4NmU0NzA3X2FmYzhfNGQwZF84YzU2XzI2ZTU5NWViYThmMCIKCnJlc3VsdCA9IHJlLnN1YihyZWdleCwgc3Vic3QsIHRlc3Rfc3RyLCAwKQpwcmludCAocmVzdWx0KQoK