如何计算 pandas 中列之间的百分比变化？

Question

I am new to Python and pandas. I created a dataframe and want to calculate the percent change between 2 columns. I know of the pct_change function in pandas but that works between rows.

import pandas as pd
import matplotlib.pyplot as plt 

UKnewcars = pd.DataFrame({
    'Model': ["Diesel", "MHEV Diesel", "Petrol", "MHEV petrol","BEV", "PHEV", "HEV" ],
    '2021': [10658,11448,94314,27326,32721,13884,24961],
    '2020': [46996,13484,176532,30382,21903,12454,26290]})

I keep getting the error message below for any formula I try even a simple subtraction that I tried between these two columns.

TypeError: unsupported operand type(s) for /: 'int' and 'str'

These are the data types of the data frame

Model    object
2021      int64
2020      int64
dtype: object

If you know how I can calculate the percent change between these columns please let me know. If it is a data type issue let me know as well. I know pandas has the int64 data type and I assume it corresponds to the int data type in Python. I have included a screenshot of how the dataframe looks like on my screen, see below:

Answer 1

Convert string column to index :

UKnewcars = UKnewcars.set_index('Model').pct_change(axis=1)
print (UKnewcars)
             2021      2020
Model                      
Diesel        NaN  3.409458
MHEV Diesel   NaN  0.177848
Petrol        NaN  0.871748
MHEV petrol   NaN  0.111835
BEV           NaN -0.330613
PHEV          NaN -0.102996
HEV           NaN  0.053243