Subtract one dataframe from another excluding the first column Pandas

Question

I have to dataframes with the same columns. My task should be to subtract the df_tot from df_nap without touching the first column (\'A\'). What is the easiest solution for it?<

Answer 1

Simply subtract the entire DataFrames, then reassign the desired values to the Wavelength column.

result = df_tot - df_nap
result['Wavelength'] = df_tot['Wavelength']

For example,

import numpy as np
import pandas as pd

df_tot = pd.DataFrame(np.random.randint(10, size=(3,4)), columns=list('ABCD'))
df_nap = pd.DataFrame(np.random.randint(10, size=(3,4)), columns=list('ABCD'))
# df_tot['A'] = df_nap['A']   # using column A as the "Wavelength" column

result = df_tot - df_nap
result['A'] = df_tot['A']

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Alternatively, or if Wavelength column were not numeric, you could subtract everything except the Wavelength, then reassign that column:

result = df_tot.drop('Wavelength', axis=1) - df_nap.drop('Wavelength', axis=1)
result['Wavelength'] = df_tot['Wavelength']