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Jumping around an input file (random access)
File Handling example from a Well House Consultants training course
More on File Handling [link]
Source code: fff Module: Y110

"""This example Python program shows how a file can
be checked to see if it has grown since the previous
time the program was read, and if it *has* grown how
the newly added data can be read"""


import os
from os.path import *
import sys

"""See how much data was handled last time. If the file
is no longer that it was then, exit the program"""


fh = open("owfar","r")
what = int(fh.readline())
fh.close
where = (os.stat("pcoder"))[6]
if where <= what:
    print "no change"
    sys.exit()

"""Open the incoming data file, seek the the newly
added data, and handle that newly added data ..."""


say = ""
fh = open("pcoder","r")
fh.seek(what,0)
for line in fh.readlines():
    parts = line.strip().split("^")
    say += "CONFIG ="+parts[0]+ " -- "
    say += "CATEGORY ="+parts[1]+ " == "
    say += "PRIORITY ="+parts[2]+ " == "
    say += "DESC ="+parts[3]+ " == "
print say

"""In this example, we're passing the newly added data
through to an operating system command (i.e. another
process) that we've started from within our Python program"

os.spawnlp (os.P_WAIT,"echo","echo",say)

print "dooone"

"""
finally, note the current length of the incoming file
so that we know whether it's been extended next time we
run this code"""

fho=open("owfar","w")
fho.write(str(where)+"\n")
fho.close()

Learn about this subject
This module and example are covered on the following public courses:
 * Learning to program in Python
 * Python Programming
Also available on on site courses for larger groups

Books covering this topic
Yes. We have over 700 books in our library. Books covering Python are listed here and when you've selected a relevant book we'll link you on to Amazon to order.

Other Examples
This example comes from our "File Handling" training module. You'll find a description of the topic and some other closely related examples on the "File Handling" module index page.

Full description of the source code
You can learn more about this example on the training courses listed on this page, on which you'll be given a full set of training notes.

Many other training modules are available for download (for limited use) from our download centre under an Open Training Notes License.

Other resources
• Our Solutions centre provides a number of longer technical articles.
• Our Opentalk forum archive provides a question and answer centre.
The Horse's mouth provides a daily tip or thought.
• Further resources are available via the resources centre.
• All of these resources can be searched through through our search engine
• And there's a global index here.

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This web site is written and maintained by Well House Consultants.

Purpose of this website
This is a sample program, class demonstration or answer from a training course. It's main purpose is to provide an after-course service to customers who have attended our public private or on site courses, but the examples are made generally available under conditions described below.

Conditions of use
Past attendees on our training courses are welcome to use individual examples in the course of their programming, but must check the examples they use to ensure that they are suitable for their job. Remember that some of our examples show you how not to do things - check in your notes. Well House Consultants take no responsibility for the suitability of these example programs to customer's needs.

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