参考文章: https://www.programiz.com/python-programming/datetime
def get_days_count(start_date_time, end_date_time): ''' 得到2个时间之间的天数 ''' assert start_date_time is not None assert end_date_time is not None return (end_date_time - start_date_time).days
In this article, you will learn to manipulate date and time in Python with the help of examples.
Python has a module named datetime to work with dates and times. Let's create a few simple programs related to date and time before we dig deeper.
Example 1: Get Current Date and Time
import datetime
datetime_object = datetime.datetime.now()
print(datetime_object)
When you run the program, the output will be something like:
2018-12-19 09:26:03.478039
Here, we have imported datetime module using import datetime
statement.
One of the classes defined in the datetime
module is datetime
class. We then used now()
method to create a datetime
object containing the current local date and time.
Example 2: Get Current Date
import datetime
date_object = datetime.date.today()
print(date_object)
When you run the program, the output will be something like:
2018-12-19
In this program, we have used today()
method defined in the date
class to get a date
object containing the current local date.
What's inside datetime?
We can use dir() function to get a list containing all attributes of a module.
import datetime
print(dir(datetime))
When you run the program, the output will be:
['MAXYEAR', 'MINYEAR', '__builtins__', '__cached__', '__doc__', '__file__', '__loader__', '__name__', '__package__', '__spec__', '_divide_and_round', 'date', 'datetime', 'datetime_CAPI', 'time', 'timedelta', 'timezone', 'tzinfo']
Commonly used classes in the datetime module are:
- date Class
- time Class
- datetime Class
- timedelta Class
datetime.date Class
You can instantiate date
objects from the date
class. A date object represents a date (year, month and day).
Example 3: Date object to represent a date
import datetime
d = datetime.date(2019, 4, 13)
print(d)
When you run the program, the output will be:
2019-04-13
If you are wondering, date()
in the above example is a constructor of the date
class. The constructor takes three arguments: year, month and day.
The variable a is a date
object.
We can only import date
class from the datetime
module. Here's how:
from datetime import date
a = date(2019, 4, 13)
print(a)
Example 4: Get current date
You can create a date
object containing the current date by using a classmethod named today()
. Here's how:
from datetime import date
today = date.today()
print("Current date =", today)
Example 5: Get date from a timestamp
We can also create date
objects from a timestamp. A Unix timestamp is the number of seconds between a particular date and January 1, 1970 at UTC. You can convert a timestamp to date using fromtimestamp()
method.
from datetime import date
timestamp = date.fromtimestamp(1326244364)
print("Date =", timestamp)
When you run the program, the output will be:
Date = 2012-01-11
Example 6: Print today's year, month and day
We can get year, month, day, day of the week etc. from the date object easily. Here's how:
from datetime import date
# date object of today's date
today = date.today()
print("Current year:", today.year)
print("Current month:", today.month)
print("Current day:", today.day)
datetime.time
A time object instantiated from the time
class represents the local time.
Example 7: Time object to represent time
from datetime import time
# time(hour = 0, minute = 0, second = 0)
a = time()
print("a =", a)
# time(hour, minute and second)
b = time(11, 34, 56)
print("b =", b)
# time(hour, minute and second)
c = time(hour = 11, minute = 34, second = 56)
print("c =", c)
# time(hour, minute, second, microsecond)
d = time(11, 34, 56, 234566)
print("d =", d)
When you run the program, the output will be:
a = 00:00:00 b = 11:34:56 c = 11:34:56 d = 11:34:56.234566
Example 8: Print hour, minute, second and microsecond
Once you create a time
object, you can easily print its attributes such as hour, minute etc.
from datetime import time
a = time(11, 34, 56)
print("hour =", a.hour)
print("minute =", a.minute)
print("second =", a.second)
print("microsecond =", a.microsecond)
When you run the example, the output will be:
hour = 11 minute = 34 second = 56 microsecond = 0
Notice that we haven't passed microsecond argument. Hence, its default value 0
is printed.
datetime.datetime
The datetime
module has a class named dateclass
that can contain information from both date and time objects.
Example 9: Python datetime object
from datetime import datetime
#datetime(year, month, day)
a = datetime(2018, 11, 28)
print(a)
# datetime(year, month, day, hour, minute, second, microsecond)
b = datetime(2017, 11, 28, 23, 55, 59, 342380)
print(b)
When you run the program, the output will be:
2018-11-28 00:00:00 2017-11-28 23:55:59.342380
The first three arguments year, month and day in the datetime()
constructor are mandatory.
Example 10: Print year, month, hour, minute and timestamp
from datetime import datetime
a = datetime(2017, 11, 28, 23, 55, 59, 342380)
print("year =", a.year)
print("month =", a.month)
print("hour =", a.hour)
print("minute =", a.minute)
print("timestamp =", a.timestamp())
When you run the program, the output will be:
year = 2017 month = 11 day = 28 hour = 23 minute = 55 timestamp = 1511913359.34238
datetime.timedelta
A timedelta
object represents the difference between two dates or times.
Example 11: Difference between two dates and times
from datetime import datetime, date
t1 = date(year = 2018, month = 7, day = 12)
t2 = date(year = 2017, month = 12, day = 23)
t3 = t1 - t2
print("t3 =", t3)
t4 = datetime(year = 2018, month = 7, day = 12, hour = 7, minute = 9, second = 33)
t5 = datetime(year = 2019, month = 6, day = 10, hour = 5, minute = 55, second = 13)
t6 = t4 - t5
print("t6 =", t6)
print("type of t3 =", type(t3))
print("type of t6 =", type(t6))
When you run the program, the output will be:
t3 = 201 days, 0:00:00 t6 = -333 days, 1:14:20 type of t3 = <class 'datetime.timedelta'> type of t6 = <class 'datetime.timedelta'>
Notice, both t3 and t6 are of <class 'datetime.timedelta'>
type.
Example 12: Difference between two timedelta objects
from datetime import timedelta
t1 = timedelta(weeks = 2, days = 5, hours = 1, seconds = 33)
t2 = timedelta(days = 4, hours = 11, minutes = 4, seconds = 54)
t3 = t1 - t2
print("t3 =", t3)
When you run the program, the output will be:
t3 = 14 days, 13:55:39
Here, we have created two timedelta
objects t1 and t2, and their difference is printed on the screen.
Example 13: Printing negative timedelta object
from datetime import timedelta
t1 = timedelta(seconds = 33)
t2 = timedelta(seconds = 54)
t3 = t1 - t2
print("t3 =", t3)
print("t3 =", abs(t3))
When you run the program, the output will be:
t3 = -1 day, 23:59:39 t3 = 0:00:21
Example 14: Time duration in seconds
You can get the total number of seconds in a timedelta object using total_seconds()
method.
from datetime import timedelta
t = timedelta(days = 5, hours = 1, seconds = 33, microseconds = 233423)
print("total seconds =", t.total_seconds())
When you run the program, the output will be:
total seconds = 435633.233423
You can also find sum of two dates and times using +
operator. Also, you can multiply and divide a timedelta
object by integers and floats.
Python format datetime
The way date and time is represented may be different in different places, organizations etc. It's more common to use mm/dd/yyyy
in the US, whereas dd/mm/yyyy
is more common in the UK.
Python has strftime()
and strptime()
methods to handle this.
Python strftime() - datetime object to string
The strftime()
method is defined under classes date
, datetime
and time
. The method creates a formatted string from a given date
, datetime
or time
object.
Example 15: Format date using strftime()
from datetime import datetime
# current date and time
now = datetime.now()
t = now.strftime("%H:%M:%S")
print("time:", t)
s1 = now.strftime("%m/%d/%Y, %H:%M:%S")
# mm/dd/YY H:M:S format
print("s1:", s1)
s2 = now.strftime("%d/%m/%Y, %H:%M:%S")
# dd/mm/YY H:M:S format
print("s2:", s2)
When you run the program, the output will be something like:
time: 04:34:52 s1: 12/26/2018, 04:34:52 s2: 26/12/2018, 04:34:52
Here, %Y
, %m
, %d
, %H
etc. are format codes. The strftime()
method takes one or more format codes and returns a formatted string based on it.
In the above program, t, s1 and s2 are strings.
-
%Y
- year [0001,..., 2018, 2019,..., 9999] -
%m
- month [01, 02, ..., 11, 12] -
%d
- day [01, 02, ..., 30, 31] -
%H
- hour [00, 01, ..., 22, 23 -
%M
- minute [00, 01, ..., 58, 59] -
%S
- second [00, 01, ..., 58, 59]
To learn more about strftime()
and format codes, visit: Python strftime().
Python strptime() - string to datetime
The strptime()
method creates a datetime
object from a given string (representing date and time).
Example 16: strptime()
from datetime import datetime
date_string = "21 June, 2018"
print("date_string =", date_string)
date_object = datetime.strptime(date_string, "%d %B, %Y")
print("date_object =", date_object)
When you run the program, the output will be:
date_string = 21 June, 2018 date_object = 2018-06-21 00:00:00
The strptime()
method takes two arguments:
- a string representing date and time
- format code equivalent to the first argument
By the way, %d
, %B
and %Y
format codes are used for day, month(full name) and year respectively.
Visit Python strptime() to learn more.
Handling timezone in Python
Suppose, you are working on a project and need to display date and time based on their timezone. Rather than trying to handle timezone yourself, we suggest you to use a third-party pytZ module.
from datetime import datetime
import pytz
local = datetime.now()
print("Local:", local.strftime("%m/%d/%Y, %H:%M:%S"))
tz_NY = pytz.timezone('America/New_York')
datetime_NY = datetime.now(tz_NY)
print("NY:", datetime_NY.strftime("%m/%d/%Y, %H:%M:%S"))
tz_London = pytz.timezone('Europe/London')
datetime_London = datetime.now(tz_London)
print("London:", datetime_London.strftime("%m/%d/%Y, %H:%M:%S"))
When you run the program, the output will be something like:
Local time: 2018-12-20 13:10:44.260462 America/New_York time: 2018-12-20 13:10:44.260462 Europe/London time: 2018-12-20 13:10:44.260462
Here, datetime_NY and datetime_London are datetime objects containing the current date and time of their respective timezone.
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