I have a device which I am controlling in a for loop. I would like to check every iteration if a .txt file has changed. If it has I want to read values and send them to the device. I am checking if file was updated like this:

os.stat("myfile.txt").stat.st_mtime

This is working fine when I manually open file, write values and save file. I want to change values by another Python script which will be run by another process. In this other script I write values to the .txt file like this:

text_file = open("myfile.txt", 'w') 
text_file.write("\n0\n0\n0")
text_file.close()

When I call open(), st_mtime changes and I load nothing because text file is empty. How to deal with this? Are there other approaches besides a text file to set new values by another Python process?

CodePudding user response：

You could try an alternate way to check if the contents have changed, by checking for MD5 checksum for example.

import hashlib
..
my_hex = hashlib.md5(text_file.read()).hexdigest()

You can now monitor my_hex every iteration to check if your file contents have changed.

CodePudding user response：

I used 3 files. I check if 3th files st_mtime has changed. I write new values to a second file, and than open and close 3th file. St_mtime of the 3th file changes so i load values from second file safely. :)