Failed to write flowfile to stdin due to the pipe has been ended

Question

I have been trying to get an excel file and process it using a python script in executestreamcommand. but it is showing this error.

Any idea on how to read excel file to stdin?

import pandas as pd
import openpyxl

df = pd.read_excel(sys.stdin)
df.to_csv(sys.stdout, index=False, header=True)