@@ -207,210 +207,241 @@ Additional modules:
207207Tkinter Life Preserver
208208----------------------
209209
210- .. sectionauthor :: Matt Conway
210+ This section is not designed to be an exhaustive tutorial on either Tk or
211+ Tkinter. For that, refer to one of the external resources noted earlier.
212+ Instead, this section provides a very quick orientation to what a Tkinter
213+ application looks like, identifies foundational Tk concepts, and
214+ explains how the Tkinter wrapper is structured.
211215
216+ The remainder of this section will help you to identify the classes,
217+ methods, and options you'll need in your Tkinter application, and where to
218+ find more detailed documentation on them, including in the official Tcl/Tk
219+ reference manual.
212220
213- This section is not designed to be an exhaustive tutorial on either Tk or
214- Tkinter. Rather, it is intended as a stop gap, providing some introductory
215- orientation on the system.
216221
217- Credits:
222+ A Hello World Program
223+ ^^^^^^^^^^^^^^^^^^^^^
218224
219- * Tk was written by John Ousterhout while at Berkeley.
225+ We'll start by walking through a "Hello World" application in Tkinter. This
226+ isn't the smallest one we could write, but has enough to illustrate some
227+ key concepts you'll need to know.
220228
221- * Tkinter was written by Steen Lumholt and Guido van Rossum.
229+ ::
222230
223- * This Life Preserver was written by Matt Conway at the University of Virginia.
231+ from tkinter import *
232+ from tkinter import ttk
233+ root = Tk()
234+ frm = ttk.Frame(root, padding=10)
235+ frm.grid()
236+ ttk.Label(frm, text="Hello World!").grid(column=0, row=0)
237+ ttk.Button(frm, text="Quit", command=root.destroy).grid(column=1, row=0)
238+ root.mainloop()
224239
225- * The HTML rendering, and some liberal editing, was produced from a FrameMaker
226- version by Ken Manheimer.
227240
228- * Fredrik Lundh elaborated and revised the class interface descriptions, to get
229- them current with Tk 4.2.
241+ After the imports, the next line creates an instance of the :class: `Tk ` class,
242+ which initializes Tk and creates its associated Tcl interpreter. It also
243+ creates a toplevel window, known as the root window, which serves as the main
244+ window of the application.
230245
231- * Mike Clarkson converted the documentation to LaTeX, and compiled the User
232- Interface chapter of the reference manual.
246+ The following line creates a frame widget, which in this case will contain
247+ a label and a button we'll create next. The frame is fit inside the root
248+ window.
233249
250+ The next line creates a label widget holding a static text string. The
251+ :meth: `grid ` method is used to specify the relative layout (position) of the
252+ label within its containing frame widget, similar to how tables in HTML work.
234253
235- How To Use This Section
236- ^^^^^^^^^^^^^^^^^^^^^^^
254+ A button widget is then created, and placed to the right of the label. When
255+ pressed, it will call the :meth: ` destroy ` method of the root window.
237256
238- This section is designed in two parts: the first half (roughly) covers
239- background material, while the second half can be taken to the keyboard as a
240- handy reference.
257+ Finally, the :meth: `mainloop ` method puts everything on the display, and
258+ responds to user input until the program terminates.
241259
242- When trying to answer questions of the form "how do I do blah", it is often best
243- to find out how to do "blah" in straight Tk, and then convert this back into the
244- corresponding :mod: `tkinter ` call. Python programmers can often guess at the
245- correct Python command by looking at the Tk documentation. This means that in
246- order to use Tkinter, you will have to know a little bit about Tk. This document
247- can't fulfill that role, so the best we can do is point you to the best
248- documentation that exists. Here are some hints:
249260
250- * The authors strongly suggest getting a copy of the Tk man pages.
251- Specifically, the man pages in the ``manN `` directory are most useful.
252- The ``man3 `` man pages describe the C interface to the Tk library and thus
253- are not especially helpful for script writers.
254261
255- * Addison-Wesley publishes a book called Tcl and the Tk Toolkit by John
256- Ousterhout (ISBN 0-201-63337-X) which is a good introduction to Tcl and Tk for
257- the novice. The book is not exhaustive, and for many details it defers to the
258- man pages.
262+ Important Tk Concepts
263+ ^^^^^^^^^^^^^^^^^^^^^
259264
260- * :file: `tkinter/__init__.py ` is a last resort for most, but can be a good
261- place to go when nothing else makes sense.
265+ Even this simple program illustrates the following key Tk concepts:
262266
267+ widgets
268+ A Tkinter user interface is made up of individual *widgets *. Each widget is
269+ represented as a Python object, instantiated from classes like
270+ :class: `ttk.Frame `, :class: `ttk.Label `, and :class: `ttk.Button `.
263271
264- A Simple Hello World Program
265- ^^^^^^^^^^^^^^^^^^^^^^^^^^^^
272+ widget hierarchy
273+ Widgets are arranged in a *hierarchy *. The label and button were contained
274+ within a frame, which in turn was contained within the root window. When
275+ creating each *child * widget, its *parent * widget is passed as the first
276+ argument to the widget constructor.
266277
267- ::
278+ configuration options
279+ Widgets have *configuration options *, which modify their appearance and
280+ behavior, such as the text to display in a label or button. Different
281+ classes of widgets will have different sets of options.
268282
269- import tkinter as tk
283+ geometry management
284+ Widgets aren't automatically added to the user interface when they are
285+ created. A *geometry manager * like ``grid `` controls where in the
286+ user interface they are placed.
270287
271- class Application(tk.Frame):
272- def __init__(self, master=None):
273- super().__init__(master)
274- self.master = master
275- self.pack()
276- self.create_widgets()
288+ event loop
289+ Tkinter reacts to user input, changes from your program, and even refreshes
290+ the display only when actively running an *event loop *. If your program
291+ isn't running the event loop, your user interface won't update.
277292
278- def create_widgets(self):
279- self.hi_there = tk.Button(self)
280- self.hi_there["text"] = "Hello World\n(click me)"
281- self.hi_there["command"] = self.say_hi
282- self.hi_there.pack(side="top")
283293
284- self.quit = tk.Button(self, text="QUIT", fg="red",
285- command=self.master.destroy)
286- self.quit.pack(side="bottom")
294+ Understanding How Tkinter Wraps Tcl/Tk
295+ ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
287296
288- def say_hi(self):
289- print("hi there, everyone!")
297+ When your application uses Tkinter's classes and methods, internally Tkinter
298+ is assembling strings representing Tcl/Tk commands, and executing those
299+ commands in the Tcl interpreter attached to your applicaton's :class: `Tk `
300+ instance.
290301
291- root = tk.Tk()
292- app = Application(master=root)
293- app.mainloop()
302+ Whether it's trying to navigate reference documentation, trying to find
303+ the right method or option, adapting some existing code, or debugging your
304+ Tkinter application, there are times that it will be useful to understand
305+ what those underlying Tcl/Tk commands look like.
294306
307+ To illustrate, here is the Tcl/Tk equivalent of the main part of the Tkinter
308+ script above.
295309
296- A (Very) Quick Look at Tcl/Tk
297- -----------------------------
310+ ::
298311
299- The class hierarchy looks complicated, but in actual practice, application
300- programmers almost always refer to the classes at the very bottom of the
301- hierarchy.
312+ ttk::frame .frm -padding 10
313+ grid .frm
314+ grid [ttk::label .frm.lbl -text "Hello World!"] -column 0 -row 0
315+ grid [ttk::button .frm.btn -text "Quit" -command "destroy ."] -column 1 -row 0
302316
303- Notes:
304317
305- * These classes are provided for the purposes of organizing certain functions
306- under one namespace. They aren't meant to be instantiated independently.
318+ Tcl's syntax is similar to many shell languages, where the first word is the
319+ command to be executed, with arguments to that command following it, separated
320+ by spaces. Without getting into too many details, notice the following:
307321
308- * The :class: `Tk ` class is meant to be instantiated only once in an application.
309- Application programmers need not instantiate one explicitly, the system creates
310- one whenever any of the other classes are instantiated.
322+ * The commands used to create widgets (like ``ttk::frame ``) correspond to
323+ widget classes in Tkinter.
311324
312- * The :class: `Widget ` class is not meant to be instantiated, it is meant only
313- for subclassing to make "real" widgets (in C++, this is called an 'abstract
314- class').
325+ * Tcl widget options (like ``-text ``) correspond to keyword arguments in
326+ Tkinter.
315327
316- To make use of this reference material, there will be times when you will need
317- to know how to read short passages of Tk and how to identify the various parts
318- of a Tk command. (See section :ref: `tkinter-basic-mapping ` for the
319- :mod: `tkinter ` equivalents of what's below.)
328+ * Widgets are referred to by a *pathname * in Tcl (like ``.frm.btn ``),
329+ whereas Tkinter doesn't use names but object references.
320330
321- Tk scripts are Tcl programs. Like all Tcl programs, Tk scripts are just lists
322- of tokens separated by spaces. A Tk widget is just its *class *, the *options *
323- that help configure it, and the *actions * that make it do useful things.
331+ * A widget's place in the widget hierarchy is encoded in its (hierarchical)
332+ pathname, which uses a ``. `` (dot) as a path separator. The pathname for
333+ the root window is just ``. `` (dot). In Tkinter, the hierarchy is defined
334+ not by pathname but by specifying the parent widget when creating each
335+ child widget.
324336
325- To make a widget in Tk, the command is always of the form::
337+ * Operations which are implemented as separate *commands * in Tcl (like
338+ ``grid `` or ``destroy ``) are represented as *methods * on Tkinter widget
339+ objects. As you'll see shortly, at other times Tcl uses what appear to be
340+ method calls on widget objects, which more closely mirror what would is
341+ used in Tkinter.
326342
327- classCommand newPathname options
328343
329- * classCommand *
330- denotes which kind of widget to make (a button, a label, a menu...)
344+ How do I...? What option does...?
345+ ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
331346
332- .. index :: single: . (dot); in Tkinter
347+ If you're not sure how to do something in Tkinter, and you can't immediately
348+ find it in the tutorial or reference documentation you're using, there are a
349+ few strategies that can be helpful.
333350
334- *newPathname *
335- is the new name for this widget. All names in Tk must be unique. To help
336- enforce this, widgets in Tk are named with *pathnames *, just like files in a
337- file system. The top level widget, the *root *, is called ``. `` (period) and
338- children are delimited by more periods. For example,
339- ``.myApp.controlPanel.okButton `` might be the name of a widget.
351+ First, remember that the details of how individual widgets work may vary
352+ across different versions of both Tkinter and Tcl/Tk. If you're searching
353+ documentation, make sure it corresponds to the Python and Tcl/Tk versions
354+ installed on your system.
340355
341- *options *
342- configure the widget's appearance and in some cases, its behavior. The options
343- come in the form of a list of flags and values. Flags are preceded by a '-',
344- like Unix shell command flags, and values are put in quotes if they are more
345- than one word.
356+ When searching for how to use an API, it helps to know the exact name of the
357+ class, option, or method that you're using. Introspection, either in an
358+ interactive Python shell or with :func: `print `, can help you identify what
359+ you need.
346360
347- For example::
361+ To find out what configuration options are available on any widget, call its
362+ :meth: `configure ` method, which returns a dictionary containing a variety of
363+ information about each object, including its default and current values. Use
364+ :meth: `keys ` to get just the names of each option.
348365
349- button .fred -fg red -text "hi there"
350- ^ ^ \______________________/
351- | | |
352- class new options
353- command widget (-opt val -opt val ...)
366+ ::
354367
355- Once created, the pathname to the widget becomes a new command. This new
356- *widget command * is the programmer's handle for getting the new widget to
357- perform some *action *. In C, you'd express this as someAction(fred,
358- someOptions), in C++, you would express this as fred.someAction(someOptions),
359- and in Tk, you say::
368+ btn = ttk.Button(frm, ...)
369+ print(btn.configure().keys())
360370
361- .fred someAction someOptions
371+ As most widgets have many configuration options in common, it can be useful
372+ to find out which are specific to a particular widget class. Comparing the
373+ list of options to that of a simpler widget, like a frame, is one way to
374+ do that.
362375
363- Note that the object name, `` .fred ``, starts with a dot.
376+ ::
364377
365- As you'd expect, the legal values for *someAction * will depend on the widget's
366- class: ``.fred disable `` works if fred is a button (fred gets greyed out), but
367- does not work if fred is a label (disabling of labels is not supported in Tk).
378+ print(set(btn.configure().keys()) - set(frm.configure().keys()))
368379
369- The legal values of *someOptions * is action dependent. Some actions, like
370- ``disable ``, require no arguments, others, like a text-entry box's ``delete ``
371- command, would need arguments to specify what range of text to delete.
380+ Similarly, you can find the available methods for a widget object using the
381+ standard :func: `dir ` function. If you try it, you'll see there are over 200
382+ common widget methods, so again identifying those specific to a widget class
383+ is helpful.
372384
385+ ::
386+
387+ print(dir(btn))
388+ print(set(dir(btn)) - set(dir(frm)))
373389
374- .. _tkinter-basic-mapping :
375390
376- Mapping Basic Tk into Tkinter
377- -----------------------------
391+ Navigating the Tcl/ Tk Reference Manual
392+ ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
378393
379- Class commands in Tk correspond to class constructors in Tkinter. ::
394+ As noted, the official `Tk commands <https://www.tcl.tk/man/tcl8.6/TkCmd/contents.htm >`_
395+ reference manual (man pages) is often the most accurate description of what
396+ specific operations on widgets do. Even when you know the name of the option
397+ or method that you need, you may still have a few places to look.
380398
381- button .fred =====> fred = Button()
399+ While all operations in Tkinter are implemented as method calls on widget
400+ objects, you've seen that many Tcl/Tk operations appear as commands that
401+ take a widget pathname as its first parameter, followed by optional
402+ parameters, e.g.
382403
383- The master of an object is implicit in the new name given to it at creation
384- time. In Tkinter, masters are specified explicitly. ::
404+ ::
385405
386- button .panel.fred =====> fred = Button(panel)
406+ destroy .
407+ grid .frm.btn -column 0 -row 0
387408
388- The configuration options in Tk are given in lists of hyphened tags followed by
389- values. In Tkinter, options are specified as keyword-arguments in the instance
390- constructor, and keyword-args for configure calls or as instance indices, in
391- dictionary style, for established instances. See section
392- :ref: `tkinter-setting-options ` on setting options. ::
409+ Others, however, look more like methods called on a widget object (in fact,
410+ when you create a widget in Tcl/Tk, it creates a Tcl command with the name
411+ of the widget pathname, with the first parameter to that command being the
412+ name of a method to call).
393413
394- button .fred -fg red =====> fred = Button(panel, fg="red")
395- .fred configure -fg red =====> fred["fg"] = red
396- OR ==> fred.config(fg="red")
414+ ::
397415
398- In Tk, to perform an action on a widget, use the widget name as a command, and
399- follow it with an action name, possibly with arguments (options). In Tkinter,
400- you call methods on the class instance to invoke actions on the widget. The
401- actions (methods) that a given widget can perform are listed in
402- :file: `tkinter/__init__.py `. ::
416+ .frm.btn invoke
417+ .frm.lbl configure -text "Goodbye"
403418
404- .fred invoke =====> fred.invoke()
405419
406- To give a widget to the packer (geometry manager), you call pack with optional
407- arguments. In Tkinter, the Pack class holds all this functionality, and the
408- various forms of the pack command are implemented as methods. All widgets in
409- :mod: `tkinter ` are subclassed from the Packer, and so inherit all the packing
410- methods. See the :mod: `tkinter.tix ` module documentation for additional
411- information on the Form geometry manager. ::
420+ In the official Tcl/Tk reference documentation, you'll find most operations
421+ that look like method calls on the man page for a specific widget (e.g.,
422+ you'll find the :meth: `invoke ` method on the
423+ `ttk::button <https://www.tcl.tk/man/tcl8.6/TkCmd/ttk_button.htm >`_
424+ man page), while functions that take a widget as a parameter often have
425+ their own man page (e.g.,
426+ `grid <https://www.tcl.tk/man/tcl8.6/TkCmd/grid.htm >`_).
412427
413- pack .fred -side left =====> fred.pack(side="left")
428+ You'll find many common options and methods in the
429+ `options <https://www.tcl.tk/man/tcl8.6/TkCmd/options.htm >`_ or
430+ `ttk::widget <https://www.tcl.tk/man/tcl8.6/TkCmd/ttk_widget.htm >`_ man
431+ pages, while others are found in the man page for a specific widget class.
432+
433+ You'll also find that many Tkinter methods have compound names, e.g.,
434+ :func: `winfo_x `, :func: `winfo_height `, :func: `winfo_viewable `. You'd find
435+ documentation for all of these in the
436+ `winfo <https://www.tcl.tk/man/tcl8.6/TkCmd/winfo.htm >`_ man page.
437+
438+ .. note ::
439+ Somewhat confusingly, there are also methods on all Tkinter widgets
440+ that don't actually operate on the widget, but operate at a global
441+ scope, independent of any widget. Examples are methods for accessing
442+ the clipboard or the system bell. (They happen to be implemented as
443+ methods in the base :class: `Widget ` class that all Tkinter widgets
444+ inherit from).
414445
415446
416447Threading model
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