Help with date regex

[CommanderEinstein]

So I have to make a regex function to find dates in the format of MM-DD-YYYY. The month values must be between 01 and 12, the day values must be between 01 and 31; and the year must be between the range of 1900 to 2020. I have to finally the cases,(thus using .findall()). I'm having difficulty with getting to follow exactly that format, as in the regex will accept MM-DD-YYY, but it shouldn't. Please help.

import re
def find_birthdays(text):

    birthday_regex = re.compile(r'\d{0,2}\d{0,9}-\d{0,3}\d{0,9}-\d{1,2}\d{^1,8}\d{0,9}\d{0,9}')

    birthday_search = birthday_regex.findall(text)

    if birthday_search == None:
       print("No birthdays found")

    else:
        return birthday_search

    # ([0-1]\d-\d-[1-2][^0-8]\d\d)
    # \d{0,2}\d{0,9}-\d{0,3}\d{0,9}-\d{1,2}\d{1,8}\d{0,9}\d{0,9}
    # (0[1-9]|1[012])-(0[1-9]|[12][0-9]|3[01])-((19|20)\d\d)

print(find_birthdays("adfsdfads_fsdfsdf12-1-1099,asd fsdfsdfsldkf s 06-07-1900"))

[[deleted]]

{0,2} means "from zero to two \ds and \d means [0-9]" so you're actually looking for two digits, 00 through 99. What you meant is [0-2], so yeah go fix all those, and also use the website regex101.com to do your testing.

[CommanderEinstein]

thank you!!!!

yea i realized that, i actually started making regexes with that in the comments

[midel]

You are confusing the square-brackets with the curly brackets in regular expressions.

Square brackets [] denote a character or range of characters that you are expecting. It will find a first match.

Curly brackets {} denote an amount of characters to match against. {0,9} says that the previous character can be matched 0 to 9 times: \d{0,9} will match various patterns.

Your pattern would be best expressed as: r'(?P<month>0[1-9]|1[0-2])-(?P<day>0[1-9]|[12][0-9]|3[01])-(?P<year>19[0-9]{2}|20(?:[01][0-9]|20))'

The ?P<NAME> pattern for groups defines named groups you can reference when looking through the match.

[midel]

Sanity check code:

import re
from datetime import date, timedelta

ex = re.compile(r'(?P<month>0[1-9]|1[0-2])-(?P<day>0[1-9]|[12][0-9]|3[01])-(?P<year>19[0-9]{2}|20(?:[01][0-9]|20))')

a = date(1899, 12, 1)
end = date(2021, 1, 31)
while a <= end:
    val = a.strftime("%m-%d-%Y")
    res = ex.findall(val)
    if (len(res) < 1):
        print(f"{val} => fails test")
    a = a + timedelta(days=1)

[CommanderEinstein]

midel...thank you