The Python function
strftime
in
line
17
of
date1.py
is implemented by calling the C function
strftime.
On macOS, this C function allows a minus sign between the
%
and the
d
in
line
18.
See
“Do not do any padding”
in the
strftime
documentation.
On Microsoft, see
“Remove leading zeros”
here.
A
<
sign
between two
numbers
tells you if the left number is smaller:
a = 10
b = 20
if a < b:
print(f"{a} is less than {b}.")
10 is less than 20.
A
<
sign between two
strings
tells you if the left string
comes earlier in alphabetical order:
a = "goodbye"
b = "hello"
if a < b:
print(f'"{a}" comes before "{b}" in alphabetical order.')
"goodbye" comes before "hello" in alphabetical order.
A
<
sign between two objects of class
datetime.date
(line
39
of
date1.py),
or between two objects of class
datetime.datetime,
tells you if the left object comes earlier in chronological order.
import datetime
a = datetime.date(2019, 12, 31)
b = datetime.date(2020, 1, 1)
if a < b:
print(f"{a} is earlier than {b}.")
2019-12-31 is earlier than 2020-01-01.
import datetime
a = datetime.datetime(2019, 12, 31, 23, 59, 59)
b = datetime.datetime(2020, 1, 1, 0, 0, 0)
if a < b:
print(f"{a} is earlier than {b}.")
2019-12-31 23:59:59 is earlier than 2020-01-01 00:00:00.
There’s a lot more stuff you can put into a
datetime
object:
microsecond,
fold,
tzinfo.
2019-12-31 2019-12-31 2019-12-31 Tuesday, December 31, 2019 (31 Dec 2019) 2019-12-31 23:59:59 2019-12-31 23:59:59 Tuesday, December 31, 2019 23:59:59 (11:59:59 PM) Wednesday, January 1, 2020 00:00:00 (12:00:00 AM) Wednesday, January 1, 2020 2019-12-31 is earlier than 2020-01-01. d is now 2020-01-01.
The
strptime
function in
line
20
of
date2.py
creates and returns an object of class
datetime.datetime.
(Unfortunately, there is no
strptime
function that creates and returns an object of class
datetime.date.)
Then the
date
function in
line
21
creates and returns an object of class
datetime.date
that has the same year, month, and day as the
datetime.datetime,
but no hour, minute, or second.
July 20, 1969 November 22, 1963 October 24, 1929 September 1, 1939 September 11, 2001 October 24, 1929 September 1, 1939 November 22, 1963 July 20, 1969 September 11, 2001
score
function in
lines
18–21
of
date2.py
and replace it with a
lambda
function
in
line
29.
dates.sort(key = lambda item: datetime.datetime.strptime(item, "%B %d, %Y").date())
datetime.date,
and then sort this new list without any
key
argument.
listOfDateObjects = \
[datetime.datetime.strptime(date, "%B %d, %Y").date() for date in dates]
listOfDateObjects.sort() #chronological order
for date in listOfDateObjects:
print(date)
1929-10-24 1939-09-01 1963-11-22 1969-07-20 2001-09-11
import datetime d = datetime.date(2019, 12, 9) print(d.strftime("%A, %B %-d, %Y")) #on macOS: Monday, December 9, 2019 print(d.strftime("%A, %B %d, %Y")) #on macOS: Monday, December 09, 2019
Monday, December 9, 2019 Monday, December 09, 2019