Find dates with Regex

Question

I am trying to write code that clean up dates in different date formats (such as 3/14/2015, 03-14-2015, and 2015/3/14) by replacing them with dates in a single, standard format. So far I have wrote my regex expression but it's not working the way I would like.

import pyperclip,re

dateRegex = re.compile(r'''
    (\d|\d{2}|\d{4})  # match 1 digit, or two digits, or four digits
    (\s|-|\.|\/) # match either a space or a dash or a period or a backslash
    (\d{2}|\d) # match either 2 digits or one
    (\s|-|\.\/) # match either a space or a dash or a period or a backslash
    (\d{4}|\d{2}) # match either 4 or 2 digits.
    ''',)

text = "12/25/0000, 10.21.1955, 10-21-1985 6-5-1995 2004/2/21 5/25/2111 4999.2.21 "
a = dateRegex.findall(text):

Any idea why this isn't working?

Have you considered just using e.g. python-dateutil? Also it's "digits", FYI. — jonrsharpe
– jonrsharpe, Commented Jul 13, 2016 at 13:54
you have random syntax things wrong with this code, such as a trailing comma after your pattern and a colon after the findall. I hope these are all just mistakes made when copying the code. Likewise, I hope those comments for each line are just for SO demonstrative purposes and not actually in your code because those wouldn't be parsed as comments but rather part of the pattern. — R Nar
– R Nar, Commented Jul 13, 2016 at 13:58

Thomas Ayoub · Accepted Answer · 2016-07-13 14:19:30Z

1

This code works (see live):

import re
p = re.compile(ur'''(\d|\d{2}|\d{4})  # match 1 didget, or two didgets, or four didgets
                    ([-\s./]) # match either a space or a dash or a period or a backslash
                    (\d{1,2}) # match either 2 digets or one
                    ([-\s./]) # match either a space or a dash or a period or a backslash
                    (\d{4}|\d{2}) # match either 4 or 2 didgets.''', re.VERBOSE)
test_str = u"12/25/0000, 10.21.1955, 10-21-1985 6-5-1995 2004/2/21 5/25/2111 4999.2.21 "

print(p.findall(test_str))

You forget the option re.VERBOSE which means:

Spaces and text after a # in the pattern are ignored

edited Jul 13, 2016 at 14:19

answered Jul 13, 2016 at 14:02

Thomas Ayoub

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4 Comments

brianhalperin Over a year ago

Awesome. Thanks for the help

brianhalperin Over a year ago

Any idea why it's only printing dates with a "-" and not printing the other formatted dates?

Casimir et Hippolyte Over a year ago

\d|\d{2}|\d{4} => \d(?:\d(?:\d{2})?)? and \d{4}|\d{2} => \d{2}(?:\d{2})?. Isn't it better like this?

Thomas Ayoub Over a year ago

@CasimiretHippolyte it indeed works too but I find it harder to read

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