os.rename() error no such file or folder exists

Question

I have been trying to create a python script that logs my data into a .dat file called 'log.dat' and every minute, rename log.dat to something else and just start writing the incoming log data to a new, empty log.dat file.

But however my os.rename line is creating a error and I have been trying to debug it for so long but it is not helping. I keep getting the same error saying

Error : Traceback (most recent call last):rov sel.:0; homenet:0(-1); current net:0;
 File "tracer.py", line 56, in <module>
main()
File "tracer.py", line 44, in main
os.rename("/home/debian/fname", "/home/debian/log-{}.dat".format(time.strftime("%y%m%d%H%M%S")))
OSError: [Errno 2] No such file or directory

This is my code :

from __future__ import print_function
def main():


#!/usr/bin/python
# get lines of text from serial port, save them to a file


    import serial, io
    import time
    import os

    s = open('log.dat', 'w')
    log = time.strftime("%Y%m%d-%H%M%S")
    s = open(log + '.dat', 'w')

    delete = 'cat /dev/null > log.dat'

    addr  = '/dev/ttyACM0'  # serial port to read data from
    baud  = 9600            # baud rate for serial port
    fname = 'log.dat'   # log file to save data in
    fmode = 'a'             # log file mode = append

    with serial.Serial(addr,9600) as pt, open(fname,fmode) as outf:
        spb = io.TextIOWrapper(io.BufferedRWPair(pt,pt,1),
            encoding='ascii', errors='ignore', newline='\r',line_buffering=$
        spb.readline()
        while (1):
            now = time.time()
            with open(fname,fmode) as outf:
                while (time.time() - now) < 60:
                      x = spb.readline()  # read one line of text from serial$
                      print (x,end='')    # echo line of text on-screen
                      outf.write(x)       # write line of text to file
                      outf.flush()        # make sure it actually gets written
                      os.rename("/home/debian/fname", "/home/debian/log-           
                                {}.dat".format(time.strftime("%y%m%d%H%M%S")))

if __name__ == '__main__':

main()

I don't understand what am I doing wrong here. Any suggestion or help is deeply appreciated.

Answer 1

try :

os.rename("/home/debian/"+fname, "/home/debian/log-           
{}.dat".format(time.strftime("%y%m%d%H%M%S")))

or:

os.rename("/home/debian/log.dat", "/home/debian/log-                             
{}.dat".format(time.strftime("%y%m%d%H%M%S")))

Answer 2

You aren't specifying an absolute path in the open call; we don't know whether the current directory is really /home/debian ; thus it is not wise to use absolute paths with os.rename . Rather write

os.rename(fname, "log-{}.dat".format(time.strftime("%y%m%d%H%M%S")))

using the same name as with open .