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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.
Checking if the user has entered a number (Lua)

In Lua, there's a difference between 0 and nil - and that means that you can easily code to ask your user to enter a number, testing the result and allowing him to enter zero as a legitimate value. That may sound like it's no big deal, but you don't want a loop to exit on a premature 0.

Here's code to ask for a numeric response:
io.write("Please enter the age of your dog: ")
stuff = tonumber (io.read())
if stuff then

and you can be assured that the chunk will run even if a zero was entered, but will not run if a non-numeric value is given. [full source code]

That extends very easily into a loop if you need to keep asking until you get a number:
while not stuff do
  io.write("Please enter the age of your dog: ")
  stuff = tonumber (io.read())
  if not stuff then print ("Duh!") end
end

with this code relying on the non-existent variable stuff returning a false at initial entry to the loop. [full source of example]
(written 2009-08-13, updated 2009-08-14)

 
Associated topics are indexed as below, or enter http://melksh.am/nnnn for individual articles
U104 - Lua - Strings and the String library.
  [1744] Lua examples, Lua Courses - (2008-08-08)
  [2348] Finding literals rather than patterns in Lua - (2009-08-11)
  [2500] Dynamically formatting your results (Lua) - (2009-11-10)
  [4274] String formatting in Lua - string.format as a wrapper for sprintf - (2014-05-07)


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Geocoding - converting address to latitude / Longitude with PHP via Google
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A fresh example - objects the Lua way
Encapsulating shared code in a Lua module
Checking if the user has entered a number (Lua)
Passing multiple results back from a function - Lua, Python, etc
See this page in French
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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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