从Python中的字符串中提取不同格式的日期

Question

I have several strings, and have identified some formats of date on them, and would like to recognize date on each string

an_2011_02_12_azar.mp3 ->this is yyyy_mm_dd
20121112_Marcel.mp3    ->this is yyyymmdd
cdani_270607.mp3       ->this is ddmmyy
lica_07_03_15.mp3      ->this is dd_mm_yy

to do so I have:

foo = """
an_2011_02_12_azar.mp3
20121112_Marcel.mp3   
cdani_270607.mp3     
lica_07_03_15.mp3  
"""
try:
    lines = foo.split('\n')
except AttributeError:
    lines = x
for line in lines:
     print(line)
     #deals with 2011_02_12 format
     match = re.search(r'\d{4}_\d{2}_\d{2}', line)
     date = datetime.datetime.strptime(match.group(), '%Y_%m_%d').date()
     print(date)

How to apply several regular expressions so it can recognize dates?

Answer 1

If you remove the underscores:

datestr = line.replace('_', '')

then there would be only two date formats to deal with: yyyymmdd or ddmmyy . Furthermore, every date string would consist of 6 to 8 digits which you could find using the regex pattern r'\\d{8}|\\d{6}' :

datestr = re.search(r'\d{8}|\d{6}', datestr).group()

The datestr could then be parsed with either

date = DT.datetime.strptime(datestr, '%d%m%y')

or

date = DT.datetime.strptime(datestr, '%Y%m%d')

The pattern r'\\d{8}|\\d{6}' would also capture some possibly non-date-like strings, such digits which represent invalid dates. We could deal with those cases by using try..except to catch ValueErrors .

---

import re
import datetime as DT

foo = """\
an_2011_02_12_azar.mp3
20121112_Marcel.mp3   
cdani_270607.mp3     
lica_07_03_15.mp3  
an_2011_13_12_azar.mp3
"""

for line in foo.splitlines():
    datestr = line.replace('_', '')
    datestr = re.search(r'\d{8}|\d{6}', datestr).group()
    try:
        # %y matches 2-digit years
        date = DT.datetime.strptime(datestr, '%d%m%y')
    except ValueError:
        try:
            # %Y matches 4-digit years
            date = DT.datetime.strptime(datestr, '%Y%m%d')
        except ValueError:
            # handle the error case
            date = None
    print('{:23} --> {}'.format(line, date))

yields

an_2011_02_12_azar.mp3  --> 2011-02-12 00:00:00
20121112_Marcel.mp3     --> 2012-11-12 00:00:00
cdani_270607.mp3        --> 2007-06-27 00:00:00
lica_07_03_15.mp3       --> 2015-03-07 00:00:00
an_2011_13_12_azar.mp3  --> None