reads a file asynchronously during its execution while somewhere some other process writes to the same file
Tested against Windows 10 / Python 3.10 / Anaconda - should work everywhere - pure Python
read_async (
file : str ,
asthread : bool = True ,
mode : str = "r" ,
action = lambda line : sys .stderr .write ((str (line ) + "\n " )),
stoptrigger : list | tuple = (False ,),
):
This function `read_async` reads a file asynchronously during its execution while somewhere some other
process writes to the same file .
Args :
file (str ): The path to the file to be read .
asthread (bool , optional ): If True , the function will start as a thread . Default is True .
mode (str , optional ): The mode in which the file is opened . Default is 'r' (read mode ).
action (function , optional ): A function to be applied to each line of the file . Default is to write the line to stderr .
stoptrigger (list | tuple , optional ): A list or tuple (preferably a list ) that triggers the function to stop reading when its last element is True . Default is [False ].
encoding (str , optional ): The character encoding of the file . Default is 'utf-8' .
errors (str , optional ): How to handle encoding errors . Default is 'backslashreplace' .
Returns :
kthread .KThread or None : If as_thread is True , it returns a KThread object . Otherwise , it returns None .
The advantage of this function is that it allows for real - time processing of the file while it is being written by another process .
This is particularly useful in scenarios where the file is continuously updated , and the updates need to be processed immediately , such as in log monitoring or real - time data analysis .
Example usage :
from threading import Timer
from time import time
newfile = f'c:\\ testfilex{ str (time ()).replace ("." ,"_" )} .txt'
stoptrigger = [False ,]
t = read_async (
file = newfile ,
as_thread = True ,
mode = "r" ,
action = lambda line : sys .stderr .write ((str (line ) + "\n " )),
stoptrigger = stoptrigger ,
)
Timer (5 , lambda : stoptrigger .append (True )).start () # Stops after 5 seconds and doesn't print anymore, but os.system goes on.
os .system ("ping 8.8.8.8 -n 10 > " + newfile + "" )
if not asthread :
return _read_file_async (file , mode = mode , action = action )
else :
return _start_as_tread (file , mode , action , stoptrigger )