[Python-de] I need help

I have line 'pythonpythonpyth'. How do I know which word is the foundation line?. Other examples: "pythonpythonpyth" is python "DOLORIUMD" is DOLORIUM "HELLOLHELLO" is HELLOL "thewordword" is thewordword I need to know whether the word in the text is repeated and get it. This will be the key.