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Python Dates and Times in Python (2014) Let's Build a Timed Quiz App Harder Time Machine

Adam Niblick
Adam Niblick
3,157 Points
Posted by Adam Niblick
Adam Niblick
3,157 Points

Is there a better way than if elif?

I am wondering if there is a better way to code this challenge than creating a bunch of "if elif" statements to catch the different possible input strings representing time duration. It seems we should be able to take the string and directly use it as the argument for the datetime.timedelta type.

import datetime

starter = datetime.datetime(2015, 10, 21, 16, 29)

def time_machine(timestr, duration):
    if timestr.lower()=='years':
        duration=duration*365
        td=datetime.timedelta(days=duration)
    elif timestr.lower()=='days':
        td=datetime.timedelta(days=duration)
    elif timestr.lower()=='hours':
        td=datetime.timedelta(hours=duration)
    elif timestr.lower()=='minutes':
        td=datetime.timedelta(minutes=duration)
    return starter + td

[MOD: added ```python formatting -cf]

1 Answer

Chris Freeman
MOD
Chris Freeman
Treehouse Moderator 68,423 Points
Chris Freeman
Chris Freeman
Treehouse Moderator 68,423 Points

There is nothing wrong with a long chain of elif statements in Python as there isn't an equivalent to the case statements of other languages.

If the code provides for catching the "years" condition you can compress the other conditions using dict expansion:

import datetime

starter = datetime.datetime(2015, 10, 21, 16, 29)

def time_machine(duration, timestr):
    if timestr.lower()=='years':
        duration=duration*365
        td=datetime.timedelta(days=duration)
    elif timestr.lower() in ['days', 'hours', 'minutes']:
        td=datetime.timedelta(**{timestr.lower():duration})
    return starter + td

Your original code had the arguments reversed: the duration integer should be first.