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Json is the new marshall, pickle and cPickle / Python

Conversion of objects into serial data, such that it can be stored in a file or passed over a network, and restoring it when read back, is a vital topic within any serious object oriented application. It's all very well working with an object on the heap (i.e. in memory while your program runs), but if you dump it out and then restore it, you're going to need to do so in such a way that it can go to a different memory location, as chances are that the addresses it was saved from are going to be in other use when you restore. Thus a serialised format, and json has beceome very much the standard - it's compact, character based rather than binary, quite flexible, and widely supported.

In Python, you may still have reasons to use marshall, pickle and cpickle, or xml, but 9 times out of 10 you'll do better using Json.

This morning I have been working with a 1 Gbyte data flow, and rather than repeat the analysis of my raw data (136 seconds elapsed time) to create the dicts and lists I want to go on and graph, I've chosen to do the extraction once and dump out the Json data to a file. Subsequent runs of my program will check for the file, and read it if present (well under a second!) - see source code here. It's going to save me an awful lot of time during the course this week (and will stop my delegates getting bored) as I'm using Json as my cache. Note the "pretty print" option I have added too - allowing my Json objects to be written raw (which would be the norm), or well formatted (which I've used to show you on our web site - data is [here].
(written 2015-02-22)

 
Associated topics are indexed as below, or enter http://melksh.am/nnnn for individual articles
Y115 - Additional Python Facilities
  [4709] Some gems from Intermediate Python - (2016-10-30)
  [4593] Command line parameter handling in Python via the argparse module - (2015-12-08)
  [4536] Json load from URL, recursive display, Python 3.4 - (2015-10-14)
  [4451] Running an operating system command from your Python program - the new way with the subprocess module - (2015-03-06)
  [4298] Python - an interesting application - (2014-09-18)
  [4211] Handling JSON in Python (and a csv, marshall and pickle comparison) - (2013-11-16)
  [4085] JSON from Python - first principles, easy example - (2013-05-13)
  [3469] Teaching dilemma - old tricks and techniques, or recent enhancements? - (2011-10-08)
  [3442] A demonstration of how many Python facilities work together - (2011-09-16)
  [3089] Python regular expressions - repeating, splitting, lookahead and lookbehind - (2010-12-17)
  [2790] Joining a MySQL table from within a Python program - (2010-06-02)
  [2786] Factory methods and SqLite in use in a Python teaching example - (2010-05-29)
  [2765] Running operating system commands from your Python program - (2010-05-14)
  [2764] Python decorators - your own, staticmethod and classmethod - (2010-05-14)
  [2746] Model - View - Controller demo, Sqlite - Python 3 - Qt4 - (2010-04-29)
  [2745] Connecting Python to sqlite and MySQL databases - (2010-04-28)
  [2721] Regular Expressions in Python - (2010-04-14)
  [2655] Python - what is going on around me? - (2010-02-28)
  [2462] Python - how it saves on compile time - (2009-10-20)
  [2435] Serialization - storing and reloading objects - (2009-10-04)
  [2407] Testing code in Python - doctest, unittest and others - (2009-09-16)
  [1876] Python Regular Expressions - (2008-11-08)
  [1337] A series of tyre damages - (2007-09-08)
  [1336] Ignore case in Regular Expression - (2007-09-08)
  [1305] Regular expressions made easy - building from components - (2007-08-16)
  [1149] Turning objects into something you can store - Pickling (Python) - (2007-04-15)
  [1136] Buffering output - why it is done and issues raised in Tcl, Perl, Python and PHP - (2007-04-06)
  [1043] Sending an email from Python - (2007-01-18)
  [901] Python - listing out the contents of all variables - (2006-10-21)
  [753] Python 3000 - the next generation - (2006-06-09)
  [672] Keeping your regular expressions simple - (2006-04-05)
  [663] Python to MySQL - (2006-03-31)
  [463] Splitting the difference - (2005-10-13)
  [239] What and why for the epoch - (2005-03-08)
  [208] Examples - Gadfly, NI Number, and Tcl to C interface - (2005-02-10)
  [183] The elegance of Python - (2005-01-19)


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Json is the new marshall, pickle and cPickle / Python
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