Get “2:35pm” instead of “02:35PM” from Python date/time?

问题

I'm still a bit slow with Python, so I haven't got this figured out beyond what's obviously in the docs, etc.

I've worked with Django a bit, where they've added some datetime formatting options via template tags, but in regular python code how can I get the 12-hour hour without a leading zero?

Is there a straightforward way to do this? I'm looking at the 2.5 and 2.6 docs for "strftime()" and there doesn't seem to be a formatting option there for this case.

Should I be using something else?

Feel free to include any other time-formatting tips that aren't obvious from the docs. =)

回答1:

Nothing built-in to datetime will do it. You'll need to use something like:

datetime.time(1).strftime('%I:%M%p').lstrip('0')

Addendum

As @naktinis points out, this is tailored to the use of this particular strftime parameter. Unfortunately, there is no generic solution if the content of the strftime parameter is unknown or unspecified (e.g. an external parameter), because it becomes a "do what I mean, not what I say" problem.

Thus, given that you have to know what's in your strftime parameter, in a more complex case you could solve this as parts:

tval = datetime.time(1)
tval_str = (tval.strftime('%A, %B ') + tval.strftime('%d').lstrip('0') 
    + tval.strftime(' %Y, ') + tval.strftime('%I:%M').lstrip('0') 
    + tval.strftime('%p').lower())

or with the re module:

tval = datetime.time(1)
tval_str = re.sub(r"^0|(?<=\s)0", "", 
    re.sub(r"(?<=[0-9])[AP]M", lambda m: m.group().lower(), 
    tval.strftime('%A, %B %d %Y, %I:%M%p')))

That said, bear in mind that if the "%p" term gives you uppercase letters, it may be because the user set their locale to work that way, and by changing case you are overriding user preferences, which sometimes leads to bug reports. Also, the user may want something other than "am" or "pm", such as "a.m." and "p.m.". Also note that these are different for different locales (e.g. en_US locale gives AM or PM for %p, but de_DE gives am or pm) and you might not be getting characters in the encoding you assume.

From the documentation on strftime behavior:

Because the format depends on the current locale, care should be taken when making assumptions about the output value. Field orderings will vary (for example, “month/day/year” versus “day/month/year”), and the output may contain Unicode characters encoded using the locale’s default encoding (for example, if the current locale is js_JP, the default encoding could be any one of eucJP, SJIS, or utf-8; use locale.getlocale() to determine the current locale’s encoding).

So, in short, if you think you need to override locale settings, make sure you have a good reason why, so you don't just end up creating new bugs.

回答2:

This question has already been answered but you can technically get "2:35pm" directly from a Python datetime with .strftime("%-I:%M%P") on linux platforms that use glibc because Python's strftime() uses the c library's strftime().

>>> import datetime
>>> now = datetime.datetime.now()
datetime.datetime(2012, 9, 18, 15, 0, 30, 385186)
>>> now.strftime("%-I:%M%P")
'3:00pm'
>>> datetime.time(14, 35).strftime("%-I:%M%P")
'2:35pm'

See strftime glibc notes on "-".

回答3:

While I'm partial to Mike DeSimone's answer, for voting purposes I think this might be a worthwhile contribution...

The Django project contains a "PHP Compatible" date formatting class in django/utils/dateformat.py (trunk). It's used like so (shell example):

>>> import datetime
>>> from django.utils.dateformat import DateFormat
>>> d = datetime.datetime.now()
>>> df =  DateFormat(d)
>>> df.format('g:ia') # Format for Hour-no-leading-0, minutes, lowercase 'AM/PM'
u'9:10a.m.'

It fulfills the requirement here, and may be worth including in your project. With that, I'll say that you should verify the license permits such use... Any comments to clarify are welcome.

回答4:

Python's strftime() is only guaranteed to support the format codes from C89 (see the list).

Useful additional format codes are defined by other standards (see the Linux man page for strftime()). For this question, the relevant additional codes are:

%l — The hour (12-hour clock) as a decimal number (range 1 to 12).
%P — Like %p but in lowercase: "am" or "pm" or a corresponding string for the current locale.

I like to use a wrapper function around strftime() to implement additional codes:

def extendedStrftime(dt, format):

    day  = dt.strftime('%d').lstrip('0')
    hour = dt.strftime('%I').lstrip('0')
    ampm = dt.strftime('%p').lower()

    format = format.replace('%e', day)
    format = format.replace('%l', hour)
    format = format.replace('%P', ampm)

    return dt.strftime(format)

To get an output in the format "2:35pm":

extendedStrftime(dt, '%l:%M%P')

It's also very common to want to format the day without the leading zero, which can be done with the additional code %e:

extendedStrftime(dt, '%e %b %Y')  # "1 Jan 2015"

回答5:

datetime.time objects expose the hour, minute and second fields. Making your own formatting with these is pretty trivial. Something like this:

return "%d:%02d %s" % (foo.hour % 12 + 0 if foo.hour % 12 else 12, #ugh
                       foo.minute,
                       "pm" if foo.hour >= 12 else "am")

回答6:

Use %l to get the hour as a number between 1..12:

In [2]: datetime.time(hour=14,minute=35).strftime('%l:%M%p')
Out[2]: ' 2:35PM'

For more format codes, see http://au2.php.net/strftime.

回答7:

I know it's pretty cheap, but you could just discard the first character if it's a zero :)

回答8:

A little hack that I've used:

# a time object
mytime = time(hour=time_hour, minute=time_minute)
# return a time as a string without a leading zero in hours.
return "%s:%s" % (mytime.hour, mytime.strftime("%M"))

来源：https://stackoverflow.com/questions/2925230/get-235pm-instead-of-0235pm-from-python-date-time

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python

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time

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