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

Posted by Gustavo Guzmán
Gustavo Guzmán
4,213 Points

How to create a function with arguments that work on the timedelta function???

I really tried, but can't find a solution that works: the aim is to create a function that takes 'minutes', 'seconds', 'days', 'years', along with an interger as arguments, and so these can be passed on to a datetime.timedelta function/method. However, timedelta is very specific about how to pass the arguments to it, e.g. 'days=4', so other arg names dont work.

I found on the internet an alternative, which would be creating a dict with the keys and values, and passing that on to the timedelta, but that still wouldn't work for this challenge!

How do you solve it?

time_machine.py 
import datetime

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

# Remember, you can't set "years" on a timedelta!
# Consider a year to be 365 days.

## Example
# time_machine(5, "minutes") => datetime(2015, 10, 21, 16, 34)

def time_machine(num, duration):
    if duration == 'years':
        travel = (datetime.timedelta(days = 365)) * num
    travel = datetime.timedelta(duration = num)
    return starter + travel

2 Answers

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

Hey Gustavo Guzmán, you’re on the right track.

Two errors to fix:

  • the second assignment to travel should be in an else: block
  • the value of duration needs to be used as the keyword argument. As it is, the string “duration” is being used as the keyword.

One method to resolve this would be to use many if/elif statements to determine the value of duration and set travel accordingly.

A trick to accomplish this in one statement is to creat a dict the unpack it as a key/value pair:

datetime.timedelta(**{duration: num})

will create a dict of {“value_of_duration”: num}, then by using **{} this key/value pair will be unrolled just like **kwargs

Edit: adding another variable to dict option:

>>> dur = "days"
>>> value = 4
>>> dict([(dur, value)])
{‘month’: 4}
>>> datetime.timedelta(**dict([(dur, value)]))
datetime.timedelta(4)

Post back if you need more help. Good luck!!!

Gustavo Guzmán
Gustavo Guzmán
4,213 Points
Gustavo Guzmán
Gustavo Guzmán
4,213 Points

Thank you very much! I've managed to get it using the many if/elifs. I didn't think it was very Pythonic, but it worked. I will definitely try the dictionary option, though, because I need to practice that.