Update a certain rows in a column to NULL in Python data frame

 You can achieve this by using the pandas library in Python. Below is the code to update the USL and LSL columns to null when the SpecTypeId is not equal to 5.

import pandas as pd
import numpy as np

# Assuming df is your data frame
partspec_insert = df[['PartId', 'PartRev', 'TestCodeId', 'SpecTypeId', 'Nominal', 'USL', 'LSL', 'TMD', 'CustomerCoA']]

# Update USL and LSL to null when SpecTypeId is not equal to 5
partspec_insert.loc[partspec_insert['SpecTypeId'] != 5, ['USL', 'LSL']] = np.nan

# Display the updated data frame
print(partspec_insert)

Explanation:

1. partspec_insert is created by selecting the specified columns from the original data frame df.
2. The loc method is used to locate rows where SpecTypeId is not equal to 5 and update the USL and LSL columns to null (represented by np.nan in pandas).