Weirdly enough, '#' is a bad directive in format '%#H:%M'

Question

I've seen a lot of similar questions, and still I don't seem to be able find out what the issue with my code is. I'm running this:

from datetime import datetime
date_st = "17:00"
date = datetime.strptime(date_st, "%#H:%M")

And I get the error:

ValueError: '#' is a bad directive in format '%#H:%M'

I'm running Windows, that's why I use %#H and not %-H. I tried %-H though and it doesn't work as well.

[The following is a list of all the format codes that the 1989 C standard requires](https://docs.python.org/3/library/datetime.html#strftime-and-strptime-format-codes) Notice how `%#` and `%-` is not listed. — It_is_Chris, Jan 27 '22 at 17:21
Why do you think it's weird? Does the Python documentation state that it should work? — Mark Ransom, Jan 27 '22 at 17:28
@It_is_Chris well, so there is no way of removing trailing zeroes within the datetime's functionality? — mykhailohoy, Jan 27 '22 at 17:28
What is your expected output based on your sample code i.e., what should `print(date)` return? — It_is_Chris, Jan 27 '22 at 17:31
@It_is_Chris 0001-01-01 17:00:00. I also want it to work for not zero-padded strings, like "2:00" — mykhailohoy, Jan 27 '22 at 17:40
@mykhailohoy then what is wrong with `print(datetime.strptime(date_st, "%H:%M"))`? — It_is_Chris, Jan 27 '22 at 18:04

score 1 · Accepted Answer · answered Jan 27 '22 at 17:54

%#H is only a valid formatting code for formatting a string (strftime), not parsing it with strptime.

I think strptime is provided by Python itself because windows doesn't have such a function, so theoretically support for #H/-H can be added. But since %H can already parse a single optional leading 0 for one-digit hours, there isn't much need for it (and POSIX strptime doesn't allow %-H).

You will have to do something else to parse it. In this case, something like:

date_no_leading_zeros = date_st.lstrip("0")
# To support strings like "00:17" for 17 minutes past midnight
if date_no_leading_zeros.startswith(":"):
    date_no_leading_zeros = "0" + date_no_leading_zeros
date = datetime.strptime(date_no_leading_zeros, "%H:%M")

would work. But in other cases, you might want to use a regex to parse the date.

You may also be able to do thi swith zfill – MYousefi Jan 27 '22 at 18:40 — MYousefi, Jan 27 '22 at 18:40

Weirdly enough, '#' is a bad directive in format '%#H:%M'

1 Answers1