Using contain or isin for comparing 2 values in a data frame-CodePudding

given a data frame (df), I would like to determine if the current Last Name contains the previous row Last Name value. I attempted using a for loop where I had an if statement of...

if df['Last Name'][index].str.contains(df['Last Name'][index-1]):
    print('yes')

The code above is incorrect. What is the best way of finding if a value of a data frame at a certain index contains another value of a data frame at a different index? I am not looking for if that value is in the column, I am only looking to see if it exists in previous row of the column.

Edit: I am not finding if both values are equal, I want to find if the current row values contains previous row value.

CodePudding user response：

You can use pandas' shift to move Last Name by by one row and check if they equal:

df['Last Name shifted'] = df['Last Name'].shift(periods=1)
equals_df = (df['Last Name shifted'] == df['Last Name shifted'])

Now equals_df is a boolean series with True / False - you can do whatever you want with it (check indices with 'True', check how many are Trues etc)

CodePudding user response：

Solved: if df['Last Name'][index] in df['Last Name'][index-1]: