Well first of all using startswith only would work if the line starts with the word, not exactly if the line contains the word. For instance, your startswith('Hello') would not work for "Hi and Hello to you!" since the string does not start with 'Hello'. What you need to use are the functions find() or index(). The difference is that find() will return -1 if the string is not found in the text and index() will throw a "ValueError" in the same case.
If either of these two methods do find the match string in the text, they will return a value that is >= 0.
# Returns 7 because character index 7 is where 'hello' starts
'Hi and hello to you'.find('hello')
# Returns -1 because 'hello' is not found
'Hi and howdy to you all'.find('hello')
# Throws a ValueError because 'hello' is not found
'Hi and howdy to you all'.index('hello')
These functions search the string from the left. You can also start your search from the right using rfind() and rindex() as well. So be sure to look up all these functions to see how to use them. They also take optional start/end parameters too that you may find of interest.
"At DIC we be python string finding code ninjas... 'Awesome, Cool, kicks ass'.find('DIC')... it never returns -1!"