tz.py 文件源码

def _find_comp(self, dt):
        if len(self._comps) == 1:
            return self._comps[0]
        dt = dt.replace(tzinfo=None)
        try:
            return self._cachecomp[self._cachedate.index(dt)]
        except ValueError:
            pass
        lastcomp = None
        lastcompdt = None
        for comp in self._comps:
            if not comp.isdst:
                # Handle the extra hour in DST -> STD
                compdt = comp.rrule.before(dt-comp.tzoffsetdiff, inc=True)
            else:
                compdt = comp.rrule.before(dt, inc=True)
            if compdt and (not lastcompdt or lastcompdt < compdt):
                lastcompdt = compdt
                lastcomp = comp
        if not lastcomp:
            # RFC says nothing about what to do when a given
            # time is before the first onset date. We'll look for the
            # first standard component, or the first component, if
            # none is found.
            for comp in self._comps:
                if not comp.isdst:
                    lastcomp = comp
                    break
            else:
                lastcomp = comp[0]
        self._cachedate.insert(0, dt)
        self._cachecomp.insert(0, lastcomp)
        if len(self._cachedate) > 10:
            self._cachedate.pop()
            self._cachecomp.pop()
        return lastcomp