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Using our JSON service from Python with cache
Already written modules example from a Well House Consultants training course
More on Already written modules [link]

This example is described in the following article(s):
   • Cacheing class for Python - using a local SQLite database as a key/value store - [link]

This example references the following resources:
http://www.wellho.net/services/pix.json')

Source code: pyjson_with_cache Module: Y117
# Using our JSON service from Python with cache

import json
import urllib2
import time
import os.path

# Get an object from a service if we don't have a recent local copy
# How long ago ago was the local file [or, later, record] modified?

# see if the local file exists too - if it doesn't set "out of date"

try:
        cachetime = os.path.getmtime("cachedrecord.txt")
except:
        cachetime = 0

if time.time() - cachetime > 20:

        # local copy is old - grab it afresh

        response = urllib2.urlopen('http://www.wellho.net/services/pix.json')
        stuff = response.read()
        source = "from remote server"

        # store the fresh copy (we are using a file ..
        # but could use memcached or another database with similar principles
        # -- that will let us cache multiple / keyed records! --

        # Trap issues if the file won't open for overwrite

        try:
                fho = open("cachedrecord.txt","w")
                fho.write(stuff)
                fho.close()
        except:
                pass
                # source = " ... CANNOT STORE TO CACHE"

else:

        # local copy is quite new. Get it our of fridge and re-serve it ;-)

        stuff = open("cachedrecord.txt","r").read()
        source = "from cache"

# We now have it as a serialised stream - in JSON format.
# turn it into an object (type dict)

memory = json.loads(stuff)

# A top level look (so the trainee can see what's happening!)

print " ---- Here is what we have ---- "
for itemname in memory.keys():
        print itemname
print "For your training info, the data is",source
print " ------------------------------- "

# or in more detail

toby = time.gmtime(memory["timedat"])
print "This was generated at",memory["timedat"],time.strftime("%c",toby)

if memory["lookfor"]:
        print "Searching only for",memory["lookfor"]
else:
        print "All available records requested"

# And look at the detailed stuff within the response too!

for record in memory["acc"]:
        print record["when"], record["which"]

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 "Already written modules" training module. You'll find a description of the topic and some other closely related examples on the "Already written modules" 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.

Web site author
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.

This program is copyright Well House Consultants Ltd. You are forbidden from using it for running your own training courses without our prior written permission. See our page on courseware provision for more details.

Any of our images within this code may NOT be reused on a public URL without our prior permission. For Bona Fide personal use, we will often grant you permission provided that you provide a link back. Commercial use on a website will incur a license fee for each image used - details on request.

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