Training, Open Source Programming Languages

This is page http://www.wellho.net/mouth/2909_Be- ... iques.html

Our email: info@wellho.net • Phone: 01144 1225 708225

 
For 2021 - online Python 3 training - see ((here)).

Our plans were to retire in summer 2020 and see the world, but Coronavirus has lead us into a lot of lockdown programming in Python 3 and PHP 7.
We can now offer tailored online training - small groups, real tutors - works really well for groups of 4 to 14 delegates. Anywhere in the world; course language English.

Please ask about private 'maintenance' training for Python 2, Tcl, Perl, PHP, Lua, etc.
Be gentle rather than macho ... regular expression techniques

Please don't be "macho" with your regular expressions.

You can write a very long and complex pattern to match something like a postcode or email address, but if you do, it's be hard to test, difficult to debug, and awkard to maintain. And to add insult to injury, it will probably run slower that the alternative approach.

"What alternative approach?" I hear you asking.

Softly, softly.

Just as you would (manuall) look at an email address quickly and say "does it have an @ symbol in the middle", do the same thing with an easier regular expression that a full, detailed match. Capture the bit before the @ (the user name) into one variable, and the bit after the @ (the domain name) into another. And only then check each of them to see if they match (a much simpler) pattern.


From last week's Python course - an example [full source]:

eare = re.compile(r"^\s*(\S+)@(\S+)\s*$")
emmas_bits = eare.findall(emma)
domain_els = emmas_bits[0][1].split(".")


The first line breaks the email address down into two chunks which it stores in the emmas_bits collection. Then the split separates the elements of the domain name at the "." characters. Much easier to read and write than trying to do it all in one!
(written 2010-08-08)

 
Associated topics are indexed as below, or enter http://melksh.am/nnnn for individual articles
Q805 - Object Orientation and General technical topics - Advanced Regular Expression Components
  [728] Looking ahead and behind in a Regular Expression - (2006-05-22)
  [3089] Python regular expressions - repeating, splitting, lookahead and lookbehind - (2010-12-17)
  [3100] Looking ahead and behind in Regular Expressions - double matching - (2010-12-23)
  [3790] Solution looking for a problem? Lookahead and Lookbehind - (2012-06-30)

Q803 - Object Orientation and General technical topics - Regular Expressions - Extra Elements
  [943] Matching within multiline strings, and ignoring case in regular expressions - (2006-11-25)
  [1336] Ignore case in Regular Expression - (2007-09-08)
  [1372] A taster PHP expression ... - (2007-09-30)
  [1601] Replacing the last comma with an and - (2008-04-04)
  [1613] Regular expression for 6 digits OR 25 digits - (2008-04-16)
  [1735] Finding words and work boundaries (MySQL, Perl, PHP) - (2008-08-03)
  [1860] Seven new intermediate Perl examples - (2008-10-30)
  [3516] Regular Expression modifiers in PHP - summary table - (2011-11-12)
  [3650] Possessive Regular Expression Matching - Perl, Objective C and some other languages - (2012-03-12)


Back to
How Green is my train?
Previous and next
or
Horse's mouth home
Forward to
Robust - testing the system
Some other Articles
Six languages in one file - an HTML++ web page
Predictions for the seagull population
Feeding the Grockles
Robust - testing the system
Be gentle rather than macho ... regular expression techniques
How Green is my train?
Dartmouth, Kingswear and Torbay
Switching from Adobe Photoshop to Gimp - testing it on animals
Defining static methods in Python
Melksham Area Board meeting of last week
4759 posts, page by page
Link to page ... 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40, 41, 42, 43, 44, 45, 46, 47, 48, 49, 50, 51, 52, 53, 54, 55, 56, 57, 58, 59, 60, 61, 62, 63, 64, 65, 66, 67, 68, 69, 70, 71, 72, 73, 74, 75, 76, 77, 78, 79, 80, 81, 82, 83, 84, 85, 86, 87, 88, 89, 90, 91, 92, 93, 94, 95, 96 at 50 posts per page


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.

Link to Ezine home page (for reading).
Link to Blogging home page (to add comments).

© WELL HOUSE CONSULTANTS LTD., 2021: 48 Spa Road • Melksham, Wiltshire • United Kingdom • SN12 7NY
PH: 01144 1225 708225 • EMAIL: info@wellho.net • WEB: http://www.wellho.net • SKYPE: wellho

PAGE: http://www.wellho.net/mouth/2909_Be- ... iques.html • PAGE BUILT: Sun Oct 11 16:07:41 2020 • BUILD SYSTEM: JelliaJamb