如何在python中通过多种格式格式化日期字符串

Question

我有三种日期格式:YYYY-MM-DD, DD.MM.YYYY, DD/MM/YYYY。

是否可以验证和解析字符串，如2014-05-18或18.5.2014或18/05/2019 ?

Answer 1

尝试每种格式，看看是否有效:

from datetime import datetime
def try_parsing_date(text):
    for fmt in ('%Y-%m-%d', '%d.%m.%Y', '%d/%m/%Y'):
        try:
            return datetime.strptime(text, fmt)
        except ValueError:
            pass
    raise ValueError('no valid date format found')

Answer 2

>>> import dateutil.parser
>>> dateutil.parser.parse(date_string)

这应该可以处理Python 2.7+中的大多数标准日期格式。如果你真的有超级自定义日期格式，你总是可以回到Jon Clements提到的那个。

Answer 3

这实际上是我面临的一个问题，我是这样处理它的，我的主要目的是日期分隔符

class InputRequest:
     "This class contain all inputs function that will be required in this program. "
      def __init__(self, stockTickerName = 'YHOO', stockSite='yahoo', startDate = None, 
             endDate = datetime.date.today()):
      def requestInput(self, requestType =''):
          "Fro requesting input from user"
          self.__requestInput = input(requestType)
          return self.__requestInput

def dateFormat(self, dateType=''):
    '''
        this function handles user date input
        this repeats until the correct format is supplied
        dataType: this is the type of date, eg: DOF, Date of Arriveal, etc 
    '''
    while True:
        try:
            dateString = InputRequest.requestInput(self,dateType)
            dtFormat = ('%Y/%m/%d','%Y-%m-%d','%Y.%m.%d','%Y,%m,%d','%Y%m%d') #you can add extra formats needed
            for i in dtFormat:
                try:
                    return datetime.datetime.strptime(dateString, i).strftime(i)
                except ValueError:
                    pass
        except ValueError:
            pass
        print('nNo valid date format found. Try again:')
        print("Date must be seperated by either [/ - , . ] (eg: 2012/12/31 --> ): ")

Answer 4

为了给@jon- elements这个已经很好的答案添加一点，

为可跟踪性的目的增加了一些异常的详细内容

from datetime import datetime
def try_parsing_date(possible_date, field):
    """
    Try to parse a date using several formats, warn about
    problematic value if the possible_date does not match
    any of the formats tried
    """
    for fmt in ('%Y-%m-%d', '%d/%m/%Y', '%m/%d/%Y'):
        try:
            return datetime.strptime(possible_date, fmt)
        except ValueError:
            pass
    raise ValueError(f"Non-valid date format for field {field}: '{possible_date}'")

这里，possible_date是可能包含日期的文本格式之一，field将是您正在测试的变量或列。这样可以更容易地找到有问题的值

Answer 5

纯python:

from datetime import datetime
my_datetime = datetime.strptime('2014-05-18', '%Y-%m-%d') 
repr(my_datetime)
>>> 'datetime.datetime(2014,5,18,0,0)'

查看datetime.strptime()格式文档获取更多格式字符串。