I'm using Tkinter for a small Python application. It has a set of ratio buttons, a text box, and a button. Is there a way to make it so the user can simply press Enter/Return on a keyboard and run the same function the button runs? The text box stays selected even when a radio is changed, so that won't cause any problems.
You should be able to bind an event handler to either the text box widget or the whole application that will be called when the event happens. Assuming you have a function to handle the event, something along the lines of:
widget.bind('<Return>', event_handler)
You can also bind a handler function at the application level by calling the bind_all() method of any widget, e.g.:
self.bind_all('<Return>', self.event_handler)
Note the key name is Return not Enter. See Key Names for a list of them all. You can also prefix the key name with a modifier like Shift- and Control- if desired.
There's a decent online reference for tkinter 8.4 here.
Related
When you want to select an item in a Treeview, you usually use the double-click:
def print_element(event):
print(my_treeview.selection()[0])
my_treeview.bind("<Double-1>", print_element)
Today I tried to do the same but using a single click instead:
my_treeview.bind("<Button-1>", print_element)
But it wouldn't work. The output was just an empty tuple.
I started to search online for an explanation... why is it not working?
EDIT:
My goal was actually to do something every time a treeview item was selected.
I proposed a solution myself using the identify() function of Tkinter
Another user proposed to use the Tkinter callback <ButtonRelease-1> which is much more appropriate
Finally, a third user focused his answer on using the Tkinter callback <<TreeviewSelect>>, which is for sure the best option
The reason it doesn't work the way you expect is because your custom single-click binding happens before the default behavior. So, when your single-click is processed, that happens before an item is selected. The second time you click, your function will print the previously selected item.
If you want to have a function called when an item is selected, you should bind to <<TreeviewSelect>>, which will fire immediately after the user selects an item with a single click or via the keyboard.
The default behavior of a treeview supports selecting multiple items at once, so the following code will print out the text of all of the selected items as a list, even if only a single item is selected. You can, of course, modify this to only print out the first selected item if you so desire.
def print_element(event):
tree = event.widget
selection = [tree.item(item)["text"] for item in tree.selection()]
print("selected items:", selection)
tree.bind("<<TreeviewSelect>>", print_element)
It is because the selection is not set yet when the <Button-1> (it is the same as <ButtonPress-1>, i.e. when the mouse button 1 is pressed and not released) event callback is called.
You should bind on <ButtonRelease-1> or <<TreeviewSelect>> instead as the selection is set when the event callback is being executed.
Why it doesn't work
When you click an item in a treeview, that item is still not in a SELECTED status in the moment the callback is activated. You are changing the status in that very moment.
Using a double-click, the first click change the status, and at the second click you are activating your callback, so the status has already been changed.
How can it work
Kudos to this website
In short,
def print_element(event):
print(my_treeview.identify('item', e.x, e.y))
my_treeview.bind("<Button-1>", print_element)
This time, print_element() will check the coordinates of the mouse, and will discover the selected item check what is under the mouse. Nice and clean!
I am developing a Text based application using Python Tkinter, In my Text widget created some words are tag_configured, on double clicking mouse on that tagged words selection appears with blue color, how can I get this selected text for further processing, Code as follows.........
self.area.tag_configure('errorword',font=('MLU-Panini', 15,foreground="black",underline=True)
self.area.tag_bind("errorword","<Double-Button-1>",self.mouse_click,add=None)
def mouse_click(self,event):
errorstr=self.area.get(tk.SEL_FIRST,tk.SEL_LAST)
print("mmmmmm",errorstr)
Shows error
File "C:\Python34\lib\tkinter\__init__.py", line 3082, in get
return self.tk.call(self._w, 'get', index1, index2)
_tkinter.TclError: text doesn't contain any characters tagged with "sel"
.......................................................................
Can someone guide me on how to solve this error.
Exactly like tobias_k mentions in his comment, the order in which the event bindings are executed is key here, because you are trying to get the selected text before the text is actually selected. You can see the order of binding execution using the bindtags() widget method. When you do this for a Text widget you will see something like
('.38559496', 'Text', '.', 'all')
Which means that the order, from left to right, of binding event execution is so that first events that are unique to this specific widget are evaluated, then those specific to the widget class, then those to your root window and finally everything else on application level (source).
Your double-click event is on widget level, since it is applied only to that specific widget, but the actual selection of the text is an event on the Text class level. Therefore, you will have to rearrange the order so that the class events come before the widget events. You can get the order by calling bindtags without arguments and then define a new order by calling it again with a tuple containing the order:
order = self.area.bindtags()
self.area.bindtags((order[1], order[0], order[2], order[3]))
This makes sure that the selection of the text is performed before you try to read the selection.
I have an Entry widget on a simple calculator. The user can choose to enter an equation via the keypad. I was wondering if there was a way to detect a character(from the keypad in my case) being typed into the Entry widget. So, focus is on the widget, user presses '4', it comes up on the widget... can I detect this act, for basic purposes of logging the input?
Every time you press a key inside a Tkinter window, a Tkinter.Event instance is created. All you need to do is access that instance. Here is a simple script that demonstrates just how:
from Tkinter import Tk, Entry
root = Tk()
def click(key):
# print the key that was pressed
print key.char
entry = Entry()
entry.grid()
# Bind entry to any keypress
entry.bind("<Key>", click)
root.mainloop()
key (being a Tkinter.Event instance) contains many different attributes that can be used to get almost any type of data you want on the key that was pressed. I chose to use the .char attribute here, which will have the script print what each keypress is.
Yes. There are a few different ways to do this, in fact.
You can create a StringVar, attach it to the Entry, and trace it for changes; you can bind all of the relevant events; or you can add a validation command that fires at any of several different points in the sequence. They all do slightly different things.
When a user types 4, there's a key event with just the 4 in it (which doesn't let you distinguish whether the user was adding 4 to the end, or in the middle, or replacing a whole selected word, or…), and then a modification event is fired with the old text,* and then the "key" or "all" validation function is called with the (proposed) new text, and the variable is updated with the (accepted) new text (unless the validation function returned false, in which case the invalidcommand is called instead).
I don't know which one of those you want, so let's show all of them, and you can play around with them and pick the one you want.
import Tkinter as tk
root = tk.Tk()
def validate(newtext):
print('validate: {}'.format(newtext))
return True
vcmd = root.register(validate)
def key(event):
print('key: {}'.format(event.char))
def var(*args):
print('var: {} (args {})'.format(svar.get(), args))
svar = tk.StringVar()
svar.trace('w', var)
entry = tk.Entry(root,
textvariable=svar,
validate="key", validatecommand=(vcmd, '%P'))
entry.bind('<Key>', key)
entry.pack()
root.mainloop()
The syntax for variable trace callbacks is a bit complicated, and not that well documented in Tkinter; if you want to know what the first two arguments mean, you need to read the Tcl/Tk docs, and understand how Tkinter maps your particular StringVar to the Tcl name 'PY_VAR0'… Really, it's a lot easier to just build a separate function for each variable and mode you want to trace, and ignore the args.
The syntax for validation functions is even more complicated, and a lot more flexible than I've shown. For example, you can get the inserted text (which can be more than one character, in case of a paste operation), its position, and all kinds of other things… but none of this is described anywhere in the Tkinter docs, so you will need to go the Tcl/Tk docs. The most common thing you want is the proposed new text as the argument, and for that, use (vcmd, '%P').
Anyway, you should definitely play with doing a variety of different things and see what each mechanism gives you. Move the cursor around or select part of the string before typing, paste with the keyboard and with the mouse, drag and drop the selection, hit a variety of special keys, etc.
* I'm going to ignore this step, because it's different in different versions of Tk, and not very useful anyway. In cases where you really need a modified event, it's probably better to use a Text widget and bind <<Modified>>.
If you just need to do simple things without using trace module you can try
def objchangetext(self, textwidget):
print(textwidget.get()) #print text out to terminal
text1 = tk.Entry(tk.Tk())
text1.bind("<KeyRelease>", lambda event, arg=(0): objchangetext(text1))
I am using tkinter for a GUI. I bound an event to an entry like so:
EntryFilePath.bind("<Key>", updateAmountOfPeople)
It works, but the problem is that it only updates when a key other than typing input is being pressed. Backspace triggers it, arrows trigger it, just not letters or numbers. I am looking for this functionality.
Other info that might be important:
PathFileName = StringVar()
EntryFilePath = Entry(topLeftMidFrame, textvariable = PathFileName, width=45)
EntryFilePath.pack(side=TOP, pady=32, padx=10)
How to make it trigger on any key?
EDIT: I found out that this only happens when it just got selected. It needs one of the "other" non [a-Z0-9] keys once, after that it is good to go. This is problematic though, in case people start immediately writing.
EDIT2: It might have to do with it having update delay.
The binding should work for every keypress -- if it's not, you're doing something somewhere else in your code to prevent it from working, or your testing is flawed.
If you want a function to be called whenever the value changes, you might want to consider setting a trace on the variable associated with the entry widget. The trace will fire whenever the value changes, no matter whether it's through keyboard input, pasting with the mouse, etc. It will not call your callback when the user uses the arrow keys or the return key, or any other key that doesn't affect the value.
For example:
def var_callback(*args):
print "the variable has changed:", PathFileName.get()
PathFileName.trace("w", var_callback)
It can be solved by changing
EntryFilePath.bind("<Key>", updateAmountOfPeople)
to
EntryFilePath.bind("<KeyRelease>", updateAmountOfPeople)
When I bind the event <Key> to an entry and read the content, the change somehow lags behind. I want to "dynamically update" another entry that shows the result of a calculation of the contents of various entries as soon as entry 1 is changed. But somehow the change is not recognized instantly, only the foregoing one. Don't know if the problem is clear, so let's say it like this:
If I make n changes, the changes up to n-1 are recognized. For example, if the number 1000 is in the entry and I press backspace twice, entry_1.get() would yield 100 instead of 10. Hope you understand what i mean now :)
Code snippet (simplified):
self.entry_1.bind('<Key>',lambda d: self.update())
def update(self):
success=True
try:
float(self.entry_1.get())
float(self.entry_2.get())
except ValueError: success=False
if success:
self.entry_3.delete(0,"end")
x=(float(self.entry_1.get())*float(self.entry_2.get())
self.entry_3.insert("end", "%g" %x)
What might be the reason for that?
The reason is due to the order that events are processed. That order is defined by the "binding tag" (or bindtag) of the widget. By default the order is widget, class, toplevel, "all". For example, if you have a binding on the widget, and on the class, and on the toplevel window that contains the widget, and on the special case "all", the bindings will fire in that order.
I gave a lengthy writeup of this problem in this answer to the question How to bind self events in Tkinter Text widget after it will binded by Text widget?