Tk locks up - 100% c.p.u. on a simple program (Tcl, Perl, Python)

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 Our training notes are now very much out of date, but due to upward compatability most of our examples remain operational and even relevant ad you are welcome to make us if them "as seen" and at your own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))

Fighting packs and grids - Tk under Tcl, Perl, Python

You'll use pack OR grid to place components into your frame in a Tcl/Tk application. You may use both pack and grid within the same program, but NOT within the same frame. If you do, not only will you be writing code that has no clear meaning, but you'll also invoke the pack and grid handlers at the same time and may cause them to fight. Have a look at this code:

button .ouch -text "do NOT press this button" -command exit

label .more -text "This is a label"

 

button .wow -text "This is a button you may press" -command exit

label .contd -text "Another BORING! label"

 

grid .more .ouch

pack .ouch .more

pack .contd .wow

grid .wow .contd

When I ran that, my prompt was lost, no wish window appeared, and my c.p.u. utilisation rocketed to 99% ... and stayed there. I guess when you have two individuals fighting, they don't show any regard at all for others around them.

Footnote I've often contended that the way to get a user to select a button is to label it "Do not push this under any circumstances" ... which is what I have put in the example above. Some may say that I have a warped sense of humour, or that I have watched too much "Trigger Happy TV".
(written 2007-09-09, updated 2007-09-11)

Associated topics are indexed as below, or enter http://melksh.am/nnnn for individual articles

Y205 - Further uses of Python
  [190] Python engines - (2005-01-26)
  [595] Add a friendly front end with Tk - (2006-02-08)
  [745] Python modules. The distribution, The Cheese Shop and the Vaults of Parnassus. - (2006-06-05)
  [1036] Python Qt, wX, TkInter, and Jython - training?? - (2007-01-16)
  [1663] Python in an afternoon - a lecture for experienced programmers - (2008-06-01)

T218 - Tcl/Tk - Geometry Managers
  [212] Tcl/Tk (wish) Grid layout example - (2005-02-12)
  [445] Sticky news - (2005-09-15)
  [787] Tk - laying out your GUI with frames, pack and grid - (2006-06-30)
  [1335] Expanding a grid - Tcl/Tk - (2007-09-07)
  [1470] fill and expand on Tcl/Tk pack command - (2007-12-13)

P307 - Perl/Tk
  [596] The magic of -textvariable - (2006-02-08)
  [599] Perl/Tk real time display - (2006-02-10)
  [738] (Perl) Callbacks - what are they? - (2006-05-30)
  [1310] Callbacks - a more complex code sandwich - (2007-08-19)
  [3009] Expect in Perl - a short explanation and a practical example - (2010-10-22)

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Some other Articles

Catching up on indexing our resources
Melksham Laundrette
Google, wwmdirectory, Freshwater, ATP - new scam?
Moving to Melksham? Househunting map.
Tk locks up - 100% c.p.u. on a simple program (Tcl, Perl, Python)
Packages and Namespaces are like Suitcases and Aircraft
Handling Binary data in Tcl (with a note on C)
A series of tyre damages
Ignore case in Regular Expression

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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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