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For 2023 (and 2024 ...) - we are now fully retired from IT training.
We have made many, many friends over 25 years of teaching about Python, Tcl, Perl, PHP, Lua, Java, C and C++ - and MySQL, Linux and Solaris/SunOS too. Our training notes are now very much out of date, but due to upward compatability most of our examples remain operational and even relevant ad you are welcome to make us if them "as seen" and at your own risk.

Lisa and I (Graham) now live in what was our training centre in Melksham - happy to meet with former delegates here - but do check ahead before coming round. We are far from inactive - rather, enjoying the times that we are retired but still healthy enough in mind and body to be active!

I am also active in many other area and still look after a lot of web sites - you can find an index ((here))
Processing data line by line - iterator in Ruby with yield

If you have a big file / flow of data in Ruby, you probably don't want to read it all in to an array before you do any processing. Not only would that mean you couldn't produce any output until you have read all the data, but it would also make for a big process - probably inefficient, possibly doing a lot of swapping, and perhaps even running out of memory.

Ruby's yield keyword allow you to suspend the operation of a method and pass control to a block defined in the calling code, which may in itself call another method. Using this technique, you can in effect write parallel code, where one method is the equivalent of a Python generator, and another method or methods perform as steps in the processing of each record of data released (one by one) by that generator.

Sample code [here].

(written 2016-05-19)

 
Associated topics are indexed as below, or enter http://melksh.am/nnnn for individual articles
R112 - Ruby - Parallelism
  [2979] Ruby - yield; parallel routines - (2010-10-01)
  [3156] Splitting data reading code from data processing code - Ruby - (2011-02-04)


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Some other Articles
Melksham Station - as at May 2016 - Part 1
Saudi Arabia or Weymouth?
One line scripts - Awk, Perl and Ruby
Ruby testing with RSpec - a new example
Processing data line by line - iterator in Ruby with yield
Reading in XML in Ruby with xmlsimple
Expect with Ruby - a training example to get you started
Swindon, Chippenham and Melksham - day trips by train to Weymouth start for 2016
Running shell (operating system) commands from within Ruby
Exceptions in Ruby - throwing, catching and using
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This is a page archived from The Horse's Mouth at http://www.wellho.net/horse/ - the diary and writings of Graham Ellis. Every attempt was made to provide current information at the time the page was written, but things do move forward in our business - new software releases, price changes, new techniques. Please check back via our main site for current courses, prices, versions, etc - any mention of a price in "The Horse's Mouth" cannot be taken as an offer to supply at that price.

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