pandas.Series.first — pandas 2.2.3 documentation (original) (raw)

Series.first(offset)[source]#

Select initial periods of time series data based on a date offset.

Deprecated since version 2.1: first() is deprecated and will be removed in a future version. Please create a mask and filter using .loc instead.

For a DataFrame with a sorted DatetimeIndex, this function can select the first few rows based on a date offset.

Parameters:

offsetstr, DateOffset or dateutil.relativedelta

The offset length of the data that will be selected. For instance, ‘1ME’ will display all the rows having their index within the first month.

Returns:

Series or DataFrame

A subset of the caller.

Raises:

TypeError

If the index is not a DatetimeIndex

See also

last

Select final periods of time series based on a date offset.

at_time

Select values at a particular time of the day.

between_time

Select values between particular times of the day.

Examples

i = pd.date_range('2018-04-09', periods=4, freq='2D') ts = pd.DataFrame({'A': [1, 2, 3, 4]}, index=i) ts A 2018-04-09 1 2018-04-11 2 2018-04-13 3 2018-04-15 4

Get the rows for the first 3 days:

ts.first('3D') A 2018-04-09 1 2018-04-11 2

Notice the data for 3 first calendar days were returned, not the first 3 days observed in the dataset, and therefore data for 2018-04-13 was not returned.