Listdir path should be a string. But i dont know what to do?

Question

im making a program to transfer .nc files to .csv files. This is the error I have and I am unsure how to fix it.

ive googled the issue and I cant find something that fits this, sorry

import os,sys
folder =("C:/Users/workexp/Downloads/weather.nc", "r")
for filename in os.listdir(folder): 
   infilename = os.path.join(folder,filename)
   if not os.path.isfile(infilename): continue
   oldbase = os.path.splitext(filename)
   newname = infilename.append('.nc,.csv')
   output = os.rename(infilename, newname)

expected to output file in a .csv but im stuck on this issue, thanks guys

Answer 1

Below code takes all the files in the 'Downloads' folder, checks if its has a .nc extension, and changes the filename to .csv

import os,sys

folder = "C:/Users/workexp/Downloads"
for filename in os.listdir(folder): 
    if os.path.isfile(filename): 
        file_name, file_extension = os.path.splitext(filename)
        if file_extension == '.nc':
            os.rename(filename,file_name+'.csv')