How to call function

[SriRajesh]

Hi,
I defined two function in a forloop, and on each iteration both function should trigger. I use below code, and I am not getting any output.

import pandas as pd
input=open(r'D:\PythonCodes\InputCSV.csv','r')
output=open(r'D:\PythonCodes\OutCSV.csv','w',newline="")

lst_file_smry=['InputCSV','InputCSV2']
in_dir='D:\\Mekala_Backupdata\PythonCodes'
out_dir='D:\\Mekala_Backupdata\PythonCodes'

file_name=in_dir+"\\"+lst_file_smry[1]
len_file_lst=len(lst_file_smry)
for i in range(len(lst_file_smry)):
    input_file= in_dir+"\\"+lst_file_smry[i]+".csv"
    output_file=out_dir+"\\"+lst_file_smry[i]+"out.csv"
    print("infile:",input_file)
    print("outfile:",output_file)
    def readxl():
        f= pd.read_csv(input_file)
    if __name__== "__main__":
        readxl()
    def write2csv():
        f.to_csv(output_file)
    if __name__== "__main__":
        write2csv()

error:

NameError: name 'f' is not defined
may be my function definition or function calling is bad.