Replace String in multiple text-files [SOLVED]

[Axel_Erfurt]

You did not create a function and your indentations are disastrous, try this

import os
import re
 
folder_path = "/home/pi/Workspace/Case_02/" # your path
target = "Format"

def str_counter(match_object):
    str_counter.count += 1
    return str(str_counter.count)
str_counter.count = 0

def  do_it(file_name):
    with open(file_name, 'r') as file :
        filedata = file.read()
        print(filedata)
     
        filedata = re.sub(re.escape(target), str_counter, filedata)
    
        print(filedata)
     
        with open(file_name, 'w') as file:
            file.write(filedata)
            file.close()
        
for name in os.listdir(folder_path):
    if name.endswith(".txt"):
        file_name = os.path.join(folder_path, name)
        do_it(file_name)