Python: List all the file names in a directory and its subdirectories and then print the results in a txt file

Question

My problem is as follows. I want to list all the file names in my directory and its subdirectories and have that output printed in a txt file. Now this is the code I have so far:

import os

for path, subdirs, files in os.walk('\Users\user\Desktop\Test_Py'):
   for filename in files:
     f = os.path.join(path, filename)
     a = open("output.txt", "w")
     a.write(str(f)) 

This lists the names of the files in the folders (there are 6) but each new file overwrites the old so there is only one file name in the output.txt file at any given time. How do I change this code so that it writes all of the file names in the output.txt file?

Answer 1

don't open a file in your for loop. open it before your for loop

like this

import os

a = open("output.txt", "w")
for path, subdirs, files in os.walk(r'C:\Users\user\Desktop\Test_Py'):
   for filename in files:
     f = os.path.join(path, filename)
     a.write(str(f) + os.linesep) 

Or using a context manager (which is better practice):

import os

with open("output.txt", "w") as a:
    for path, subdirs, files in os.walk(r'C:\Users\user\Desktop\Test_Py'):
       for filename in files:
         f = os.path.join(path, filename)
         a.write(str(f) + os.linesep) 

Answer 2

You are opening the file in write mode. You need append mode. See the manual for details.

change

a = open("output.txt", "w")

to

a = open("output.txt", "a")

Answer 3

You can use below code to write only File name from a folder.

import os

a = open("output.txt", "w")
for path, subdirs, files in os.walk(r'C:\temp'):
   for filename in files:
      a.write(filename + os.linesep)