In my code, why doesn't my list sort from the earliest to the latest in dates?

Question

from datetime import date, timedelta, time, datetime

# 1 Complete read_date()
def read_date(date_object):
    """Read a string representing a date in the format 2121-04-12, create a
    date object from the input string, and return the date object
    """
    dt_string = '2121-04-12'
    date_object = datetime.strptime(date_object, '%Y-%m-%d').date()
    return date_object
# 2. Use read_date() to read four (unique) date objects, putting the date objects in a list
date1 = input()
date2 = input()
date3 = input()
date4 = input()

date1_read = read_date(date1)
date2_read = read_date(date2)
date3_read = read_date(date3)
date4_read = read_date(date4)

list_date = []
list_date.append([date1, date2, date3, date4])
split_list = 

# 3. Use sorted() to sort the dates, earliest first
list_sorted = sorted(list_date)
print(list_sorted)
# 4. Output the sorted_dates in order, earliest first, in the format mm/dd/yy
new_format = 
# 5. Output the number of days between the last two dates in the sorted list
#    as a positive number

# 6. Output the date that is 3 weeks from the most recent date in the list

# 7. Output the full name of the day of the week of the earliest day

Under #3, I need to sort the dates from earliest in a specific format. I need help sorting the list as my code does not sort it. I also need help in formatting the entire list in a specific way.

Asked By: Tarun REX

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Source

Answer 1

The dates are not sorted because you are assigning the datetime object to the variables date?_read, which are never added to the list_date before applying the sorted() built-in function.
That means the list elements are sorted as strings, not as dates.
Here are the steps you asked for, that are kind of self-explanatory, I’d like though to have more datails about point 6, which doesn’t tell much, 3 weeks in the past? In the future?

from datetime import date, timedelta, time, datetime
import sys

# 1 Complete read_date()
def read_date(date_object):
    """Read a string representing a date in the format 2121-04-12, create a
    date object from the input string, and return the date object
    """
    date_object = datetime.strptime(date_object, '%Y-%m-%d').date()
    return date_object

# 2. Use read_date() to read four (unique) date objects, putting the date objects in a list

list_date = []
n_dates = 4

# Here you could check with an infinite loop the inputs
# Not being the main request, I opted for a more straightforward version
try: 
    for _ in range(n_dates):
        list_date.append(read_date(input()))
except ValueError:
    print('Invalid format')
    sys.exit(1) 

# 3. Use sorted() to sort the dates, earliest first
list_sorted = sorted(list_date)
print(list_sorted)

# 4. Output the sorted_dates in order, earliest first, in the format mm/dd/yy
for date in list_sorted:
    print(date.strftime('%m/%d/%y'))
# 5. Output the number of days between the last two dates in the sorted list
#    as a positive number
print(abs((list_sorted[-1] - list_sorted[-2]).days))

# 6. Output the date that is 3 weeks from the most recent date in the list
# 3 weeks ??
 
# 7. Output the full name of the day of the week of the earliest day
print(list_sorted[0].strftime('%A'))

Answered By: Manu62

In my code, why doesn't my list sort from the earliest to the latest in dates?

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