pandas.core.groupby.SeriesGroupBy.shift

SeriesGroupBy.shift(periods=1, freq=None, fill_value=<no_default>, suffix=None)

Shift each group by periods observations.

If freq is passed, the index will be increased using the periods and the freq.

Parameters:

periodsint | Sequence[int], default 1

Number of periods to shift. If a list of values, shift each group by each period.

freqstr, optional

Frequency string.

fill_valueoptional

The scalar value to use for newly introduced missing values.

Changed in version 2.1.0: Will raise a ValueError if freq is provided too.

suffixstr, optional

A string to add to each shifted column if there are multiple periods. Ignored otherwise.

Returns:

Series or DataFrame

Object shifted within each group.

See also

Index.shift

Shift values of Index.

Examples

For SeriesGroupBy:

>>> lst = ["a", "a", "b", "b"]
>>> ser = pd.Series([1, 2, 3, 4], index=lst)
>>> ser
a    1
a    2
b    3
b    4
dtype: int64
>>> ser.groupby(level=0).shift(1)
a    NaN
a    1.0
b    NaN
b    3.0
dtype: float64

For DataFrameGroupBy:

>>> data = [[1, 2, 3], [1, 5, 6], [2, 5, 8], [2, 6, 9]]
>>> df = pd.DataFrame(
...     data,
...     columns=["a", "b", "c"],
...     index=["tuna", "salmon", "catfish", "goldfish"],
... )
>>> df
           a  b  c
    tuna   1  2  3
  salmon   1  5  6
 catfish   2  5  8
goldfish   2  6  9
>>> df.groupby("a").shift(1)
              b    c
    tuna    NaN  NaN
  salmon    2.0  3.0
 catfish    NaN  NaN
goldfish    5.0  8.0