Controlling program flow in Python, when should I handle an invalid or None response from a method?

Question

I am new to Python and I want to know am controlling the flow of the program correctly. I am wondering if the following method is the correct way to return a value from a method.

extract_nouns() retunes an empty string if there are no nouns in news_story, the same with extract_numbers(). If search terms.

find_news() returns a list of Story objects if there are any stories, or None if no news story are found.

find_similar_news_stories() returns None unless there is a story to return.

Is this correct, or does it look wrong? Should I explicitly return None if I find no stories. Should I pass an empty list from find_news() to the method that calls find_similar_stories() and handle the checking of list there?

def find_similar_news_stories(self, news_story):
    nouns = self.extract_nouns(news_story)
    numbers = self.extract_numbers(news_story)
    search_terms = nouns + numbers
    if search_terms != "":
        stories = self.find_news(search_terms)
        if stories != None:
            return stories
        stories = self.find_news(nouns)
        return stories

Why do `extract_nouns()` and `extract_numbers()` return an empty string instead of `None` as the other functions do? — Stop harming Monica, Apr 11 '18 at 13:37
@Goyo So that I can append them even if one returns an empty string. Should I return None and have a try catch block at that point? — bloopiebloopie, Apr 11 '18 at 13:40
Then why do `find_news()` and `find_similar_news_stories()` return `None` instead of an empty sequence as the other functions do? — Stop harming Monica, Apr 12 '18 at 20:19

score 0 · Answer 1 · answered Apr 11 '18 at 13:17

It can be of any ways

If the method is called by another method for just process then pass the result as it is thus it should be explicitly handled by the calling method.

If the method is call by end user he need to know the result of the process so the handling should be done in this method itself.

Controlling program flow in Python, when should I handle an invalid or None response from a method?

1 Answers1