My Hangman game in Python
One thing I would do is wrap this up in a hangman class. That way you could just toss away the hangman instance for a new one if the user ever decided to play again rather than resting all global variables. It would also decouple the handling of user input from the actual game. If the game size would grow this would make catching bugs a lot easier. 

But lets focus on some smaller things that are easier to change 

chosen = random.choice(word_list)
return chosen


Here your variable has no purpose, I would do

return random.choice(word_list)


Similar kind of story here 

if again.lower().startswith('y'):
        return True
    return False


to 

return again.lower().startswith('y')


Next is avoid magic constants at all costs, for example 

if len(line.strip()) &gt; 3:


What is 3? Why is 3 important here? You should replace this with a global ALL_CAPS variable to represent what 3 is.