Read from a log file as it's being written using python

Take a look at this PDF starting at page 38, ~slide I-77 and you'll find all the info you need. Of course the rest of the slides are amazing, too, but those specifically deal with your issue:

import timedef follow(thefile):    thefile.seek(0,2) # Go to the end of the file    while True:        line = thefile.readline()        if not line:            time.sleep(0.1) # Sleep briefly            continue        yield line

You could try with something like this:

import timewhile 1:    where = file.tell()    line = file.readline()    if not line:        time.sleep(1)        file.seek(where)    else:        print line, # already has newline

Example was extracted from here.

As this is Python and logging tagged, there is another possibility to do this.

I assume this is based on a Python logger, logging.Handler based.

You can just create a class that gets the (named) logger instance and overwrite the emit function to put it onto a GUI (if you need console just add a console handler to the file handler)

Example:

import loggingclass log_viewer(logging.Handler):    """ Class to redistribute python logging data """    # have a class member to store the existing logger    logger_instance = logging.getLogger("SomeNameOfYourExistingLogger")    def __init__(self, *args, **kwargs):         # Initialize the Handler         logging.Handler.__init__(self, *args)         # optional take format         # setFormatter function is derived from logging.Handler          for key, value in kwargs.items():             if "{}".format(key) == "format":                 self.setFormatter(value)         # make the logger send data to this class         self.logger_instance.addHandler(self)    def emit(self, record):        """ Overload of logging.Handler method """        record = self.format(record)        # ---------------------------------------        # Now you can send it to a GUI or similar        # "Do work" starts here.        # ---------------------------------------        # just as an example what e.g. a console        # handler would do:        print(record)

I am currently using similar code to add a TkinterTreectrl.Multilistbox for viewing logger output at runtime.

Off-Side: The logger only gets data as soon as it is initialized, so if you want to have all your data available, you need to initialize it at the very beginning. (I know this is what is expected, but I think it is worth being mentioned.)