Determining when a column value changes in pandas dataframe

Learn, how to determine when a column value changes in pandas dataframe?
Submitted by Pranit Sharma, on December 09, 2022

Pandas is a special tool that allows us to perform complex manipulations of data effectively and efficiently. Inside pandas, we mostly deal with a dataset in the form of DataFrame. DataFrames are 2-dimensional data structures in pandas. DataFrames consist of rows, columns, and data.

Problem statement

Suppose we are given a data frame with two columns and we need to find a way so we can determine that the change happened between the two rows.

Determining when a column value changes

For this purpose, we will first create a data frame with 2 columns A and B, E and then we will create a new column C. We will use the diff() method with column B and store the result in column C. This will assign 1 and 0 values in column C which represents where the values are changed and where not.

We will then filter the data according to a specific condition.

Let us understand with the help of an example,

Python program to determine when a column value changes in pandas dataframe

# Importing pandas
import pandas as pd

# Creating a dictionary
d = {
    'A':[1,2,3,4,5],
    'B':[1,2,3,4,5]
}

# Creating a dataframe
df = pd.DataFrame(d)

# Display original DataFrame
print("Original DataFrame:\n",df,"\n")

# Creating a new column
df['C'] = df['B'].diff()

# Filter result
res = df[df['C'] != 0]

# Display result
print("Result:\n",res,"\n")