| 3429 | |
| 3430 | |
| 3431 | class Shift(MapOverlap): |
| 3432 | _parameters = ["frame", "periods", "freq"] |
| 3433 | _defaults = {"periods": 1, "freq": None} |
| 3434 | |
| 3435 | func = M.shift |
| 3436 | enforce_metadata = True |
| 3437 | transform_divisions = False |
| 3438 | align_dataframes = True |
| 3439 | |
| 3440 | @functools.cached_property |
| 3441 | def clear_divisions(self): |
| 3442 | # TODO We can do better if freq is given, but this needs adjustments in |
| 3443 | # map_partitions |
| 3444 | return True if self._divisions()[0] is None or self.freq is not None else False |
| 3445 | |
| 3446 | def _divisions(self): |
| 3447 | if self.freq is None: |
| 3448 | return self.frame.divisions |
| 3449 | divisions = _calc_maybe_new_divisions(self.frame, self.periods, self.freq) |
| 3450 | if divisions is None: |
| 3451 | divisions = (None,) * (self.frame.npartitions + 1) |
| 3452 | return divisions |
| 3453 | |
| 3454 | @functools.cached_property |
| 3455 | def _meta(self): |
| 3456 | return make_meta(meta_nonempty(self.frame._meta).shift(**self.kwargs)) |
| 3457 | |
| 3458 | @functools.cached_property |
| 3459 | def kwargs(self): |
| 3460 | return dict(periods=self.periods, freq=self.freq) |
| 3461 | |
| 3462 | def _simplify_up(self, parent, dependents): |
| 3463 | if isinstance(parent, Projection): |
| 3464 | return plain_column_projection(self, parent, dependents) |
| 3465 | |
| 3466 | @property |
| 3467 | def before(self): |
| 3468 | return self.periods if self.periods > 0 else 0 |
| 3469 | |
| 3470 | @property |
| 3471 | def after(self): |
| 3472 | return 0 if self.periods > 0 else -self.periods |
| 3473 | |
| 3474 | |
| 3475 | class ShiftIndex(Blockwise): |