Pandas DataFrame interpolate() Method

Replace NULL values with the number between the previous and next row:

In this example we use a .csv file called data.csv

import pandas as pd

df = pd.read_csv('data.csv')

newdf = df.interpolate(method='linear')

Definition and Usage

The interpolate() method replaces the NULL values based on a specified method.

dataframe.interpolate(method, axis, inplace, limit, limit_direction, limit_area, downcast, kwargs)

The parameters are keyword arguments.

Parameter	Value	Description
method	`'linear' 'akima' 'barycentric' 'cubic' 'cubispline' 'from_derivates' 'index' 'krogh' 'nearest' 'pad' 'pchip' 'piecewise_polynomial' 'polynomial' 'quadric' 'slinear' 'spline' 'time' 'zero' 'bfill' 'pad' 'ffill' None`	Optional, default 'linear' . Specifies the method to use when replacing NULL values
axis	`0 1 'index' 'columns'`	Optional, default 0. The axis to fill the NULL values along
inplace	`True False`	Optional, default False. If True: the replacing is done on the current DataFrame. If False: returns a copy where the replacing is done.
limit	Number `None`	Optional, default None. Specifies the maximum number of NULL values to fill (if method is specified)
limit_direction	`'forward' 'backward' 'both'`	Optional, default 'forward', (if the method is backfill or bfill, the default limit_direction is 'backward'. Specifies the direction of the filling.
limit_area	`None 'inside' 'outside'`	Optional, default None. Specifies restricitons of the filling: None - No restrictions 'inside' - Fill only NULL values inside valid values 'outside' - Fill only NULL values outside valid values
downcast	Dictionary `None`	Optional, a dictionary of values to fill for specific data types

A DataFrame with the result, or None if the inplace parameter is set to True.