I would like to write a small program that has a database of coupons and their expiration dates. I chose to store them in a dictionary format, where the key is the name of an item and the value is the expiration date.
coupons: dict = {'Rice':'2024-04-03',
'Caviar':'2024-04-05',
'Granola':'2024-08-10',
'Eggs':'2024-04-02'}
Within that, there is a function that goes through every item in the dictionary to check if the coupon is still good or not (date < today), and remove the coupon if it can no longer be used.
At first, I stored the dates in the datetime(2024,4,4) format in the dict itself, I could use that for comparison to check the number of expired ones in the list but otherwise returns the TypeError: 'datetime.datetime' object is not iterable when I want to remove it from the dictionary. So now I tried changing it to a string and use it that way. Here's what I have now:
def couponCheck(db: dict[str,str]) -> dict:
expired: int = 0
now: datetime = datetime.now()
for i in db:
b = time.strptime(db.get(i),'%Y-%m-%d')
if b < now:
expired += 1
db.pop(i, None)
if expired > 1:
print(f'I found {expired} expired coupons in your catalog.')
elif expired == 1:
print('There was one expired coupon in your catalog.')
else:
print('I couldn\'t find any expired coupons. Yay!')
This results in the following error:
TypeError: '<' not supported between instances of 'time.struct_time' and 'datetime.datetime'
How could I properly compare the two dates (now and the value) in a way that can also be removed from the dict by a fuction?
By storing your dates as strings in the form of YYYY-MM-DD you can perform lexical comparisons. In fact, that's precisely why that portable format is so widely used.
Therefore, in this case you could do this:
from datetime import datetime
coupons: dict[str, str] = {
"Rice": "2024-04-03",
"Caviar": "2024-04-05",
"Granola": "2024-08-10",
"Eggs": "2024-04-02",
}
today = datetime.strftime(datetime.now(), "%Y-%m-%d")
for k, v in coupons.copy().items():
if v < today:
del coupons[k]
print(coupons)
Output:
{'Caviar': '2024-04-05', 'Granola': '2024-08-10'}