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1 # Python's datetime strftime doesn't handle dates before 1900. |
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2 # These classes override date and datetime to support the formatting of a date |
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3 # through its full "proleptic Gregorian" date range. |
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4 # |
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5 # Based on code submitted to comp.lang.python by Andrew Dalke |
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6 # |
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7 # >>> datetime_safe.date(1850, 8, 2).strftime("%Y/%M/%d was a %A") |
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8 # '1850/08/02 was a Friday' |
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9 |
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10 from datetime import date as real_date, datetime as real_datetime |
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11 import re |
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12 import time |
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13 |
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14 class date(real_date): |
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15 def strftime(self, fmt): |
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16 return strftime(self, fmt) |
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17 |
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18 class datetime(real_datetime): |
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19 def strftime(self, fmt): |
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20 return strftime(self, fmt) |
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21 |
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22 def combine(self, date, time): |
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23 return datetime(date.year, date.month, date.day, time.hour, time.minute, time.microsecond, time.tzinfo) |
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24 |
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25 def date(self): |
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26 return date(self.year, self.month, self.day) |
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27 |
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28 def new_date(d): |
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29 "Generate a safe date from a datetime.date object." |
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30 return date(d.year, d.month, d.day) |
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31 |
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32 def new_datetime(d): |
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33 """ |
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34 Generate a safe datetime from a datetime.date or datetime.datetime object. |
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35 """ |
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36 kw = [d.year, d.month, d.day] |
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37 if isinstance(d, real_datetime): |
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38 kw.extend([d.hour, d.minute, d.second, d.microsecond, d.tzinfo]) |
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39 return datetime(*kw) |
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40 |
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41 # This library does not support strftime's "%s" or "%y" format strings. |
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42 # Allowed if there's an even number of "%"s because they are escaped. |
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43 _illegal_formatting = re.compile(r"((^|[^%])(%%)*%[sy])") |
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44 |
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45 def _findall(text, substr): |
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46 # Also finds overlaps |
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47 sites = [] |
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48 i = 0 |
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49 while 1: |
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50 j = text.find(substr, i) |
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51 if j == -1: |
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52 break |
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53 sites.append(j) |
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54 i=j+1 |
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55 return sites |
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56 |
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57 def strftime(dt, fmt): |
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58 if dt.year >= 1900: |
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59 return super(type(dt), dt).strftime(fmt) |
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60 illegal_formatting = _illegal_formatting.search(fmt) |
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61 if illegal_formatting: |
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62 raise TypeError("strftime of dates before 1900 does not handle" + illegal_formatting.group(0)) |
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63 |
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64 year = dt.year |
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65 # For every non-leap year century, advance by |
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66 # 6 years to get into the 28-year repeat cycle |
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67 delta = 2000 - year |
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68 off = 6 * (delta // 100 + delta // 400) |
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69 year = year + off |
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70 |
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71 # Move to around the year 2000 |
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72 year = year + ((2000 - year) // 28) * 28 |
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73 timetuple = dt.timetuple() |
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74 s1 = time.strftime(fmt, (year,) + timetuple[1:]) |
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75 sites1 = _findall(s1, str(year)) |
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76 |
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77 s2 = time.strftime(fmt, (year+28,) + timetuple[1:]) |
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78 sites2 = _findall(s2, str(year+28)) |
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79 |
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80 sites = [] |
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81 for site in sites1: |
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82 if site in sites2: |
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83 sites.append(site) |
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84 |
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85 s = s1 |
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86 syear = "%4d" % (dt.year,) |
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87 for site in sites: |
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88 s = s[:site] + syear + s[site+4:] |
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89 return s |