Non-zero padding formats

[jedzill4]

Hi and thank you for the nice work!
I'm having an issue with non-zero padding datetime extraction, for example matching a 1/11/2017 string with format %-d/%m/%Y. The RegexGenerator class match correctly the pattern, but the DatetimeExtractor cannot extract the pattern as datetime object.

My problem is in the __parse_match_into_maybe_datetime function, in the strptime conversion. I'm using python 3.10 on linux and strptime doesn't accept the %-d directive, but can handle correctly the %d even when there is no zero padding.
From what I have read may be a platform issue and work without problems on other python implementation (anaconda maybe?). The workaround that I found is to replace all %- to their standard version (e.i. %-d to %d)

[stephen-zhao]

Thanks for reporting this and taking a look.

Python's strptime basically calls the C library underneath the hood. We can take a look at the linux docs for their version: https://man7.org/linux/man-pages/man3/strftime.3.html

It seems that the - extension is available for Glibc implementation, but are not POSIX-compliant. Furthermore, this cheatsheet claims that the Windows implementation can handle # in its place. However, it would be best to avoid platform-specific directives if possible, and if not possible to handle them individually.

That being said, it seems like the python strptime does handle zero-padding automatically as you mention, according to Note 9 on this page: https://docs.python.org/3/library/datetime.html#strftime-and-strptime-format-codes

We're open to a PR if you would like to make the change!