Formatting date string in Python for dates prior to 1900?

Question

Can anyone explain the best way to format a date time string in Python where the date value is prior to the year 1900? strftime requires dates later than 1900.

Answer 1

It's a bit cumbersome, but it works (at least in stable versions of python):

>>> ts = datetime.datetime(1895, 10, 6, 16, 4, 5)
>>> '{0.year}-{0.month:{1}}-{0.day:{1}} {0.hour:{1}}:{0.minute:{1}}'.format(ts, '02')
'1895-10-06 16:04'

note that str would still produce a readable string:

>>> str(ts)
'1895-10-06 16:04:05'

edit
The closest possible way to emulate the default behaviour is to hard-code the dictionary such as:

>>> d = {'%Y': '{0.year}', '%m': '{0.month:02}'}    # need to include all the formats
>>> '{%Y}-{%m}'.format(**d).format(ts)
'1895-10'

You'll need to enclose all format specifiers into the curly braces with the simple regex:

>>> re.sub('(%\w)', r'{\1}', '%Y-%m-%d %H sdf')
'{%Y}-{%m}-{%d} {%H} sdf'

and at the end we come to simple code:

def ancient_fmt(ts, fmt):
    fmt = fmt.replace('%%', '%')
    fmt = re.sub('(%\w)', r'{\1}', fmt)
    return fmt.format(**d).format(ts)

def main(ts, format):
    if ts.year < 1900:
        return ancient_format(ts, fmt)
    else:
        return ts.strftime(fmt)

where d is a global dictionary with keys corresponding to some specifiers in strftime table.

edit 2
To clarify: this approach will work only for the following specifiers: %Y, %m, %d, %H, %M, %S, %f, i.e., those that are numeric, if you need textual information, you'd better off with babel or any other solution.