column standardization pandas

columns = ['A', 'B','C'] #specify the column names
for col in columns:
  df[col] = (df[col] - df[col].mean())/df[col].std() 
  

Here is what the above code is Doing:
1. We create a list of column names that we want to standardize.
2. We iterate through the list of column names.
3. For each column name, we subtract the mean of the column from each value in the column.
4. For each column name, we divide each value in the column by the standard deviation of the column.
5. We overwrite the existing column with the standardized values.

Note that we are not creating new columns, we are overwriting the existing columns.