Hands on the datetime Module in Python

Things on this page are fragmentary and immature notes/thoughts of the author. Please read with your own judgement!

Comment¶

A Datetime object cannot be compared with a string directly. However, pandas Series of datetime objects can be compared with string date directly (both by operators and methods). The comparison is done by parsing the string to a datetime object. An exception will be thrown if the string cannot be parsed into a datetime object.

import datetime

Construct a date/datetime Object from String¶

datetime.datetime.strptime("2017-01-09", "%Y-%m-%d")

datetime.datetime(2017, 1, 9, 0, 0)

Time in micro seconds resolution.

datetime.datetime.strptime("2017-01-18 09:21:29.000000", "%Y-%m-%d %H:%M:%S.%f")

datetime.datetime(2017, 1, 18, 9, 21, 29)

Use suffixing zeros if nano seconds is provided.

datetime.datetime.strptime("2017-01-18 09:21:29.000000000", "%Y-%m-%d %H:%M:%S.%f000")

datetime.datetime(2017, 1, 18, 9, 21, 29)

Construct a date/datetime Object by Specifying Year, Month, Day, etc.¶

datetime.date(2017, 1, 9)

datetime.date(2017, 1, 9)

Construct a date/datetime Object from Timestamp¶

datetime.fromtimestamp(t3)

now/today¶

Get the current system time.

datetime.now()

datetime.datetime(2018, 5, 6, 4, 24, 0, 949796)

str(datetime.now())

'2018-05-06 10:11:57.277133'

datetime.today()

datetime.datetime(2018, 5, 6, 4, 23, 58, 870716)

Get timezone name. By default, datetime is not aware of timezone.

Get the current UTC time.

utcnow¶

datetime.utcnow()

datetime.datetime(2018, 5, 6, 4, 9, 42, 210413)

datetime.utcnow().date()

datetime.date(2018, 5, 6)

It seems that now and today are equivalent.

date¶

datetime.now().date()

datetime.date(2018, 5, 6)

Timzezone¶

By default, datetime is not aware of timezone which is fucking stupid! For this reason, the utcnow does return UTC time at all!

datetime.today().tzname()

datetime.now().tzname()

now and utcnow are the same, which is fucking stpid and error-prone!

print(datetime.now())
print(datetime.utcnow())

2018-05-06 04:25:45.744147
2018-05-06 04:25:45.744282

Timestamp¶

https://stackoverflow.com/questions/3682748/converting-unix-timestamp-string-to-readable-date

datetime.now().timestamp()

1525600136.106702

datetime.utcnow().timestamp()

1525600384.425062

datetime.fromtimestamp(datetime.now().timestamp())

datetime.datetime(2018, 5, 6, 10, 11, 1, 920892)

Month Day¶

date.today().day

11

Weekday¶

Monday is 0 and Sunday is 6.

today = date.today()
today

datetime.date(2017, 10, 11)

date.today().weekday() - 5 + 7

4

today - 4

---------------------------------------------------------------------------
TypeError                                 Traceback (most recent call last)
<ipython-input-18-ac1ac82a5046> in <module>()
----> 1 today - 4

TypeError: unsupported operand type(s) for -: 'datetime.date' and 'int'

TimeDelta¶

Arithmatical operation is supported via the TimeDelta class.

https://stackoverflow.com/questions/441147/how-can-i-subtract-a-day-from-a-python-date

from datetime import date, timedelta

d = date.today() - timedelta(days=1)
d

datetime.date(2018, 6, 28)

timedelta(days=1).days

1

Convert a `datetime` Object to String¶

By default, a datetime object is convertd to a string using the format %Y-%m-%d %H:%M:%S.%f. Please refer to Format Date and Time in Python for more details on how format a datetime object.

now = datetime.datetime.now()
now

datetime.datetime(2020, 3, 11, 11, 53, 42, 533996)

str(now)

'2020-03-11 11:53:42.533996'

f"The time now is {now}"

'The time now is 2020-03-11 11:53:42.533996'