Python Rotating log handler adding data in all the files

I have the below log setup in python:

def log_setup(logger_name, log_file, level=logging.ERROR):
l = logging.getLogger(logger_name)
formatter = logging.Formatter('%(asctime)s %(message)s')
fileHandler = logging.FileHandler(log_file, mode='a')
fileHandler.setFormatter(formatter)
streamHandler = logging.StreamHandler()
streamHandler.setFormatter(formatter)

l.setLevel(level)
l.addHandler(fileHandler)
l.addHandler(streamHandler)


where log_file is the path to the file. I was using above function as :

debug_file = logs_path + 'myfile_debug.log'
log_setup('debug', debug_file) #debug_file is path to the log file
log_debug = logging.getLogger('debug')


I wanted to add RotatingFileHandler so modified the above code to below:

RotatingFileHandler

def log_setup(logger_name, log_file, level=logging.ERROR):
l = logging.getLogger(logger_name)
formatter = logging.Formatter('%(asctime)s %(message)s')
fileHandler = logging.FileHandler(log_file, mode='a')
fileHandler.setFormatter(formatter)
streamHandler = logging.StreamHandler()
streamHandler.setFormatter(formatter)

handler = RotatingFileHandler(log_file, maxBytes=20, backupCount=4) #ADDED

l.setLevel(level)
l.addHandler(fileHandler)
l.addHandler(streamHandler)
l.addHandler(handler) #ADDED


When this was executed, it created 4 log file and each log file contains 1 line of log.

So for ex, if below is the actual logs:

Connected to device id MACHINE1
Connected to Internet TRUE
Connected to hub TRUE
Publishing data FALSE


Then after modification, it was like below:

myfile_debug.log.1 contains: Connected to device id MACHINE1

Connected to device id MACHINE1

myfile_debug.log.2 contains: Connected to Internet TRUE

Connected to Internet TRUE

myfile_debug.log.3 contains: Connected to hub TRUE

Connected to hub TRUE

myfile_debug.log.4 contains: Publishing data FALSE

Publishing data FALSE

myfile_debug.log contains: {All the logs}

{All the logs}

I thought it would create a new file once the size exceed. Why is this showing this behavior? Thanks

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