I'm trying to convert a date that is in the format of YYYYMMDD to MM/DD/YYYY as it is being read from a database and written to an Excel file. Using Perl I would do the following:
var=~s/([0-9])([0-9])([0-9])([0-9])([0-9])([0-9])([0-9])([0-9])/$5$6\/$7$8\/$1$2$3$4/;
Keeping in mind that this is all happening in a "for row in rows" loop structure that is reading in the database info.
Any help would be very much appreciated.
instead of using a regular expression you can use pythons datetime module.
or you could combine the two, however it is you want, but this would be a more clear way to modify date formatting. python is a language where clarity and easy reading are as important as efficiency. looking at the code below one can see that i am modifying a datestamp, whereas using a regular expression it is quite unclear sometimes.
read the datetime element and then write it as you want:
>>> from datetime import datetime
>>> datestring = '20121212' # 2012 / 12 /12
>>> datetime.strptime(datestring, '%Y%m%d').strftime('%m/%d/%Y')
'12/12/2012'
You don't need to use a regex -- Python doesn't encourage them in the same way Perl does -- but you can certainly use one:
import re
re.sub(r'(\d{4})(\d{2})(\d{2})', r'\2/\3/\1', datestring)
I would go for simple string operations - certainly no less clear...
>>> s = '20121213'
>>> '/'.join( (s[4:6], s[6:], s[:4]) )
'12/13/2012'
as opposed to:
>>> re.sub(r'(\d{4})(\d{2})(\d{2})', r'\2/\3/\1', s)
'12/13/2012'
If you're going to insist using an re like you've posted below though
dateFormatted = row["TRADE_DATE"] dateFormatted = re.sub(r'(\d)(\d)(\d)(\d)(\d)(\d)(\d)(\d)', r'\5\6/\7\8/\1\2\3\4', dateFormatted) – user1901341 5 mins ago
Then you could (ab)use string formatting as such
>>> '{4}{5}/{6}{7}/{0}{1}{2}{3}'.format(*s)
'12/13/2012'
I think you can get to it simply here, without regex:
>>> s = '20121225'
>>> conv = '/'.join((s[6:8], s[4:6], s[0:4]))
>>> conv
'25/12/2012'
remodule at all?