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今天的日期

datetime.date.today() 或 datetime.datetime.now()

>>> import datetime>>> datetime.date.today()datetime.date(2021, 4, 10)>>> d=datetime.date.today()>>> print(d)2021-04-10>>> type(d)
   

日期的偏移

用函数 datetime.timedelta(days=diff) 来实现：

>>> import datetime>>> datetime.date.today()datetime.date(2021, 4, 10)>>> d=datetime.date.today()>>>>>> d+datetime.timedelta(5)datetime.date(2021, 4, 15)>>> d-datetime.timedelta(5)datetime.date(2021, 4, 5)>>> d+datetime.timedelta(-5)datetime.date(2021, 4, 5)

日期型转日期字符串——

昨天、今天、明天的字符串形式

方法一：

>>> def strDate(diff=0):    '''返回今天或前/后diff天的日期格式字符串'''    import datetime as dt    d=dt.date.today()+dt.timedelta(days=diff)    return '{0:04}/{1:02}/{2:02}'.format(d.year,d.month,d.day)>>> strDate(-1)'2021/04/09'>>> strDate()'2021/04/10'>>> strDate(1)'2021/04/11'>>>>>> strDate(3)'2021/04/13'>>> strDate(30)'2021/05/10'>>> strDate(31)'2021/05/11'>>> strDate(365)'2022/04/10'>>> strDate(366)'2022/04/11'>>> strDate(-3)'2021/04/07'>>> strDate(-30)'2021/03/11'>>> strDate(-31)'2021/03/10'>>> strDate(-365)'2020/04/10'>>> strDate(-366)'2020/04/09'>>>

方法二：除了用format()函数转换外，datetime 自带转换方法： .strftime()

>>> import datetime as dt>>> d=dt.date.today()>>> ddatetime.date(2021, 4, 10)>>> type(d)
   
    >>>>>> d=d.strftime('%Y-%m-%d')>>> d'2021-04-10'>>> type(d)
    
   

方法三： f-string  (版本要求： Python3.6+)

>>> import datetime as dt>>> d=dt.datetime.today()>>> ddatetime.datetime(2021, 4, 10, 11, 59, 54, 531850)>>> f'{d.year}/{d.month:02}/{d.day:02}''2021/04/10'>>> f'{d.year}-{d.month:02}-{d.day:02}''2021-04-10'

 日期字符串转日期型

datetime.datetime.strptime(dateString,'格式化串')

>>> dateString = '2020/3/23'>>> datetime.datetime.strptime(dateString, '%Y/%m/%d')datetime.datetime(2020, 3, 23, 0, 0)>>> dateString = '2020-03-23'>>> datetime.datetime.strptime(dateString, '%Y/%m/%d')Traceback (most recent call last):  File "
   
    ", line 1, in 
    
         datetime.datetime.strptime(dateString, '%Y/%m/%d')  File "E:\Python\lib\_strptime.py", line 568, in _strptime_datetime    tt, fraction, gmtoff_fraction = _strptime(data_string, format)  File "E:\Python\lib\_strptime.py", line 349, in _strptime    raise ValueError("time data %r does not match format %r" %ValueError: time data '2020-03-23' does not match format '%Y/%m/%d'>>> datetime.datetime.strptime(dateString, '%Y-%m-%d')datetime.datetime(2020, 3, 23, 0, 0)# 错： datetime.datetime.strptime('2020/03/23', '%Y-%m-%d')# 错： datetime.datetime.strptime('2020-03-23', '%Y/%m/%d')# 参数的格式必须前后一致，否则报错 time data format not match
    
   

附一： 日期格式化符

附二： datetime库类列表