Copy and append data from .dat file

[ibreeden]

No you must close the file. But you changed the indentation. It should be:

import time
import schedule    
starttime=time.time()
 
 
 
#Input_file: "C:\\Campbellsci\\LoggerNet\\CR1000_Table1.dat"
#Output_file: "C:\\Users\\Makada\\Desktop\\CR1000_Table1 - kopie.dat"
 
while True:
    """ Not to append duplicate data to output file"""
    existingLines = set(line.strip() for line in open("C:\\Users\\Makada\\Desktop\\CR1000_Table1 - kopie.dat"))
    outfile = open("C:\\Users\\Makada\\Desktop\\CR1000_Table1 - kopie.dat", "a+")
    for content in open("C:\\Campbellsci\\LoggerNet\\CR1000_Table1.dat", "r"):
        if content.strip() not in existingLines: # to void duplicate lines
            outfile.write(content)
            existingLines.add(content)
    outfile.close()
 
    time.sleep(60 - time.time() % 60)