Reading streaming data sources

What if the data that is coming from the source is continuous? What if we need to read continuous data? This recipe will demonstrate a simple solution that will work for many common real-life scenarios, though it is not universal and you will need to modify it if you hit a special case in your application.

How to do it...

In this recipe, we will show you how to read an always-changing file and print the output. We will use the common Python module to accomplish this.

import time
import os
import sys

if len(sys.argv) != 2:
    print >> sys.stderr, "Please specify filename to read"

filename = sys.argv[1]

if not os.path.isfile(filename):
    print >> sys.stderr, "Given file: \"%s\" is not a file" % filename

with open(filename,'r') as f:
    # Move to the end of file
    filesize = os.stat(filename)[6]
    f.seek(filesize)

    # endlessly loop
    while True:
        where = f.tell()
        # try reading a line
        line = f.readline()
      ...