Interesting Intro to python problem I can't solve.

[deanhystad]

I'm a lot older than 48 and I am doing homework right now. I figure I'll stop doing homework a few minutes before I stop breathing.

Your "effort" crashes because flag is only defined when the age entered < 0.

I would replace this:

if dog_age < 0 :
    flag = True

with

if dog_age < 0:
    raise ValueError

You already have an exception handler, you may as well use it.

You can also simplify the comparisons and your math:

        if dog_age < 0 :
            raise ValueError
        elif dog_age <= 1 :
            dog_age_in_Human_years = dog_age * 15.0
        elif dog_age <= 2 :
            dog_age_in_Human_years = dog_age * 12.0