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Training, Open Source Programming Languages |
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| For 2023 - 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 Our training notes are now very much out of date, but due to upward compatability most of our examples remain operational and even relevant ad you are welcome to make us if them "as seen" and at your own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)) |
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The magic of -textvariable
If you're writing a GUI based application, you'll need to hold pertinent information in variables in your program, AND display that pertinent information to the user. The obvious way of doing this is to provide code that updates the display as required - in the case of Tcl/Tk you might write .wname configure -text "Melksham" to change the text on the button called "wname" to Melksham, and set usersays [.wenter cget -text] to read the text that the user's put into an entry box. But there's a better alternative. Many widgets support the -textvariable option which allows the widget to be a reflection of the variable in your program all the time - in other words, if your program changes a variable then it will be automatically updated within the widget display, and if the user changes text within an entry box that's set up with this feature, then the variable within your program is automatically updated. Examples: entry .username -textvariable uname label .host -textvariable hostsystemname Complete source code examples - A Tcl/Tk form In a Tcl/Tk popup message box A Perl/Tk example (written 2006-02-08, updated 2006-06-05) Associated topics are indexed as below, or enter http://melksh.am/nnnn for individual articles T223 - Tcl/Tk - Textish Widgets[1475] Tcl/Tk - updating your display while tasks are running - (2007-12-16) P307 - Perl/Tk [595] Add a friendly front end with Tk - (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) [1340] Tk locks up - 100% c.p.u. on a simple program (Tcl, Perl, Python) - (2007-09-09) [3009] Expect in Perl - a short explanation and a practical example - (2010-10-22)
Some other Articles
It costs nothing to say THANK YOUShould we cruise around the world? Storing a regular expression in a perl variable The magic of -textvariable Twice is a co-incidence and three times is a pattern Finding where the disc space has gone NOT Gone phishing Key facts - SQL and MySQL |
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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 pageThis 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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