[ValueError] _strptime.py can't handle 12-hr format strings using '0' instead of '12' for noon and midnight

[CatPawFreed]

BPO	33631
Nosy	@ammaraskar

^{Note: these values reflect the state of the issue at the time it was migrated and might not reflect the current state.}

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GitHub fields:

assignee = None
closed_at = <Date 2018-05-24.07:47:55.108>
created_at = <Date 2018-05-24.07:29:39.651>
labels = ['type-bug', 'invalid']
title = "[ValueError] _strptime.py can't handle 12-hr format strings using '0' instead of '12' for noon and midnight"
updated_at = <Date 2018-05-24.09:10:54.009>
user = 'https://bugs.python.org/CatPawFreed'

bugs.python.org fields:

activity = <Date 2018-05-24.09:10:54.009>
actor = 'CatPaw Freed'
assignee = 'none'
closed = True
closed_date = <Date 2018-05-24.07:47:55.108>
closer = 'ammar2'
components = []
creation = <Date 2018-05-24.07:29:39.651>
creator = 'CatPaw Freed'
dependencies = []
files = []
hgrepos = []
issue_num = 33631
keywords = []
message_count = 3.0
messages = ['317541', '317542', '317546']
nosy_count = 2.0
nosy_names = ['ammar2', 'CatPaw Freed']
pr_nums = []
priority = 'normal'
resolution = 'not a bug'
stage = 'resolved'
status = 'closed'
superseder = None
type = 'behavior'
url = 'https://bugs.python.org/issue33631'
versions = []

[CatPawFreed]

I have to process some data which date was specified in 12-hour format, eg. 9/24/2017 0:39:41 PM.
I call datetime.datetime.strptime with "%m/%d/%Y %I:%M:%S %p" format.
However, it throws me an error [File "C:\Python27\lib\_strptime.py", line 332, in _strptime (data_string, format)) ValueError: time data '9/24/2017 0:39:41 PM' does not match format '%m/%d/%Y %I:%M:%S %p'].
Then, I found out that, in _strptime.py, the regex patterns are defined as below.

        'd': r"(?P<d>3[0-1]|[1-2]\d|0[1-9]|[1-9]| [1-9])",
        'f': r"(?P<f>[0-9]{1,6})",
        'H': r"(?P<H>2[0-3]|[0-1]\d|\d)",
        'I': r"(?P<I>1[0-2]|0[1-9]|[1-9])",
        'j': r"(?P<j>36[0-6]|3[0-5]\d|[1-2]\d\d|0[1-9]\d|00[1-9]|[1-9]\d|0[1-9]|[1-9])",
        'm': r"(?P<m>1[0-2]|0[1-9]|[1-9])",
        'M': r"(?P<M>[0-5]\d|\d)",
        'S': r"(?P<S>6[0-1]|[0-5]\d|\d)",
        'U': r"(?P<U>5[0-3]|[0-4]\d|\d)",
        'w': r"(?P<w>[0-6])",

I'm a newbie in python world. Is it a bug?
I changed regex pattern of 'I' to r"(?P<I>1[0-2]|0[0-9]|[0-9])" and it works.
I would like to know why 0 is excluded.
May be, I have missed something.

[ammaraskar]

0 is excluded because it is not a valid hour in the 12 hour clock.

0:39pm is not a valid time on a 12 hour clock. After 11am you reach 12pm, then 1pm. See the table on the right here: https://en.wikipedia.org/wiki/12-hour_clock

Your data source is encoding the time incorrectly, see this thread here for some solutions: https://stackoverflow.com/a/33317167

[CatPawFreed]

Thanks for answering my question and giving me a solution.
This issue has been dawned on me that these convention are quite strange. I feel confused when thinking of 12:00am/pm vs 0:00am/pm. (@_@) (^~^)