datetime_safe.py 2.8 KB

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  1. # coding=utf-8
  2. # From django.utils.datetime_safe
  3. # Python's datetime strftime doesn't handle dates before 1900.
  4. # These classes override date and datetime to support the formatting of a date
  5. # through its full "proleptic Gregorian" date range.
  6. #
  7. # Based on code submitted to comp.lang.python by Andrew Dalke
  8. #
  9. # >>> datetime_safe.date(1850, 8, 2).strftime("%Y/%m/%d was a %A")
  10. # '1850/08/02 was a Friday'
  11. from __future__ import unicode_literals
  12. from datetime import date as real_date
  13. from datetime import datetime as real_datetime
  14. import re
  15. import time
  16. class date(real_date):
  17. def strftime(self, fmt):
  18. return strftime(self, fmt)
  19. class datetime(real_datetime):
  20. def strftime(self, fmt):
  21. return strftime(self, fmt)
  22. def combine(self, date, time):
  23. return datetime(date.year, date.month, date.day,
  24. time.hour, time.minute, time.microsecond,
  25. time.tzinfo)
  26. def date(self):
  27. return date(self.year, self.month, self.day)
  28. def new_date(d):
  29. """Generate a safe date from a datetime.date object."""
  30. return date(d.year, d.month, d.day)
  31. def new_datetime(d):
  32. """
  33. Generate a safe datetime from a datetime.date or datetime.datetime object.
  34. """
  35. kw = [d.year, d.month, d.day]
  36. if isinstance(d, real_datetime):
  37. kw.extend([d.hour, d.minute, d.second, d.microsecond, d.tzinfo])
  38. return datetime(*kw)
  39. # This library does not support strftime's "%s" or "%y" format strings.
  40. # Allowed if there's an even number of "%"s because they are escaped.
  41. _illegal_formatting = re.compile(r"((^|[^%])(%%)*%[sy])")
  42. def _findall(text, substr):
  43. # Also finds overlaps
  44. sites = []
  45. i = 0
  46. while True:
  47. j = text.find(substr, i)
  48. if j == -1:
  49. break
  50. sites.append(j)
  51. i = j + 1
  52. return sites
  53. def strftime(dt, fmt):
  54. if dt.year >= 1900:
  55. return super(type(dt), dt).strftime(fmt)
  56. illegal_formatting = _illegal_formatting.search(fmt)
  57. if illegal_formatting:
  58. msg = 'strftime of dates before 1900 does not handle {0}'
  59. raise TypeError(msg.format(illegal_formatting.group(0)))
  60. year = dt.year
  61. # for every non-leap year century, advance by
  62. # 6 years to get into the 28-year repeat cycle
  63. delta = 2000 - year
  64. off = 6 * (delta // 100 + delta // 400)
  65. year += off
  66. # move to around the year 2000
  67. year += ((2000 - year) // 28) * 28
  68. timetuple = dt.timetuple()
  69. s1 = time.strftime(fmt, (year,) + timetuple[1:])
  70. sites1 = _findall(s1, str(year))
  71. s2 = time.strftime(fmt, (year + 28,) + timetuple[1:])
  72. sites2 = _findall(s2, str(year + 28))
  73. sites = []
  74. for site in sites1:
  75. if site in sites2:
  76. sites.append(site)
  77. s = s1
  78. syear = "%04d" % (dt.year,)
  79. for site in sites:
  80. s = s[:site] + syear + s[site + 4:]
  81. return s