I'm using Python and Tkinter to create a GUI for a program I'm writing, and I'm having a couple of problems.
I have three objects descended from LabelFrame in an object descended from Frame. One of the LabelFrame descendants is two columns of corresponding Label and Entry objects.
The problem is that there are a varying number of Label and Entry pairs, and there can be more than fit on the screen. I need a way to make a scrollbar for this LabelFrame so that everything fits on the screen. I've tried various ways of making a Scrollbar object, but nothing seems to work. How can I bind a scrollbar to this frame?
Also, I need to be able to refresh or reload this LabelFrame when the load_message() method is called, but it just redisplays the new pairs on top of the old ones (so when there are less pairs in the new set, the old set is still visible at the bottom). I've tried using grid_forget() but either nothing changes or the whole frame doesn't display. How can I forget this display and then redisplay it?
Here is the code for this class:
class freq_frame(LabelFrame):
def __init__(self, master = None, text = 'Substitutions'):
LabelFrame.__init__(self, master, text = text)
self.grid()
def load_message(self):
self.frequency = get_freq(message)
self.create_widgets()
def create_widgets(self):
self.label_list = [Label(self, text = get_label(char, self.frequency[char]), justify = LEFT) for char in self.frequency.keys()]
self.entry_list = [Entry(self, width = 1) for char in self.frequency.keys()]
for n in range(len(self.label_list)):
self.label_list[n].grid(column = 0, row = n)
for n in range(len(self.entry_list)):
self.entry_list[n].grid(column = 1, row = n)
If anyone can help with either of these problems, I'd appreciate it.
Also, this question seems like it might be a little thin, but I don't know what to add. Don't hesitate to ask for more information (but be specific).
Thanks!
Labelframes don't support scrolling. So the short answer to your question is "you can't". It sounds obvious, but if the documentation for a widget doesn't say it supports scrolling, it doesn't support scrolling.
However, there is a simple solution. First, add a canvas as a child to the labelframe and pack it so that it fills the labelframe. Attach scrollbars to the canvas and add them to the labelframe too. Then embed a frame within the canvas, add your widgets to that inner frame, and then adjust the scrollregion of the canvas to match the size of the frame after you've added all the inner labels and entries.
It sounds complicated, but it's really very straight-forward.
As for re-creating the widgets when you call load_message, calling grid_forget only removes them from view, it doesn't actually destroy the widgets. Over time you could potentially end up with hundreds of non-visible widgets which is almost certainly not what you want.
Instead, you want to first destroy all the existing widgets. That's pretty easy if they all are in the same parent, since you can ask the parent for a list of all its children. Just iterate over that list to delete each child, then add any new children. An even easier solution is to destroy and recreate that inner frame that contains the labels and entries. When you delete a widget, all child widgets get automatically destroyed. So, delete that inner frame, create a new one, and add your labels and entries again.
Related
Tkinter Requirements
So I am relatively new to using tkinter and I am struggling with a very specific doubt here. I tried finding solutions to this but as much as I find it obvious, the solution to this doesn't seem to be easy to understand. So if you can see the image above, I am trying to create a GUI for a particular project which requires multi-layer (I am calling it 3D array based) widgets.
Let's say the variables used for this pointer system are i, j, and k.
I am creating individual layer widgets using for loop:
for n in range(i):
frame_x[i] = Frame(root).grid(row = 1, column = i)
entry_x[i] = Entry(frame_x[i]).grid(row = 2, column = i)
button_x[i] = Button(frame_x[i]).grid(row=3, column = i)
Please note this is not a functional code, I have tried to keep it to the point just to give an idea of the method I am using. (Let me know if you want a more detailed code block.)
Now coming to the problem. I am able to do the basic part of this. But the problem is that I want it to work dynamically.
Let's say if the user enters j = 4 first. 4 blocks will be created.
Later if he changes the value to j = 2 and the presses the button, ideally it should make the widgets at block j= 3 and 4 disappear. But I guess tkinter works on overlapping basis and doesn't change a grid element until something is specifically overlapped over it. How do I do that. I tried destroying the entire frame just after entering the for loop, but that doesn't work as for the first time no widget is created before destroying and python throws NameError saying I can't use a variable before assignment.
Anyways, please let me know how do I do this efficiently.
And also in general, if there is a better way to go about the whole thing. Please refer the image above and let me know if it doesn't make sense.
I am not very comfortable with classes in general. I prefer the inefficient way by only using functions to do everything I have to. So it would be great if you can share me a framework without using classes. But its okay if you use them. I know I should start working with classes at some point.
First off, I want to address this part of the question:
I guess tkinter works on overlapping basis and doesn't change a grid element until something is specifically overlapped over it.
I'm not entirely sure what you mean by that, but if it means what I think it means, it is a false statement. tkinter doesn't "work on an overlapping basis". If you destroy a widget, it is destroyed. It doesn't matter if it's overlapped or not.
Based on the tiny bit of code you posted, the main problem is that you aren't putting the entry and button in the frame. Because of that, they are not destroyed when you destroy the frame.
The reason you aren't putting the widgets into the frame is because of this line:
frame_x[i] = Frame(root).grid(row = 1, column = i)
In python, when you do x=y().z(), x has the value of z(). Thus, when you do frame_x[i] = Frame(...).grid(...), frame_x[i] has the value of .grid(...), and .grid(...) always returns None. Thus, frame_x[i] will be None.
When you next do entry_x[i] = Entry(frame_x[i]).grid(...), it's the same as doing entry_x[i] = Entry(None).grid(...). Because the master of the Entry is None, it becomes a child of the root window.
So, the first step is to separate the creation of the widget from the layout of the widget.
frame_x[i] = Frame(root)
frame_x[i].grid(row = 1, column = i)
Once you do that, the Entry and Button widgets will become a child of the frame, and you can remove widgets you don't want by destroying the frame (eg: frame_x[i].destroy()), since destroying a widget will also cause all children of the widget to be destroyed.
Once you have that in place, you can destroy unwanted widgets by simply calling .destroy() on the frame. For example, if you have previously created 10 groups and now need only 5, you can destroy the others and then remove them from the list like this:
# assume 'num' contains the number of frames that we want,
# and that it is smaller than the number of items in frames_x
for frame in frames_x[num:]:
frame.destroy()
frames_x = frames_x[:num]
Here is a complete working program to illustrate. Enter a number and click the button. It will create that many frame+entry+button combinations. Enter a new number that is larger or smaller and it will either add or remove widgets.
This would be easier if you used classes, but you specifically asked for a solution that doesn't use classes. In your real code you probably need to also save the entry widgets in an array so that you can reference them later, but this example is focuses on the creation of the widgets rather than writing your whole program for you.
import tkinter as tk
frames_x = [] def create_widgets():
global frames_x
num = int(num_widgets.get())
# if the number is less than the previous number of
# widgets, delete the widgets we no longer want
for frame in frames_x[num:]:
frame.destroy()
frames_x = frames_x[:num]
# if the number is greater than the previous number of
# widgets, create additional widgets
for i in range(len(frames_x), num):
# create new widget
frame = tk.Frame(root, bd=1, relief="raised")
entry = tk.Entry(frame)
button = tk.Button(frame, text="click me")
# pack entry and button in frame
button.pack(side="right")
entry.pack(side="left", fill="x", expand=True)
# grid the frame in the parent
frame.grid(row=i+1, column=0, columnspan=2)
# save the new frame in the array
frames_x.append(frame)
root = tk.Tk() num_widgets = tk.Entry(root) button = tk.Button(root, text="Create widgets", command=create_widgets)
button.grid(row=0, column=1) num_widgets.grid(row=0, column=0, sticky="ew")
root.mainloop()
I am creating a gui with tkinter in python. I have created a scrollbar and this is what the section of code looks like:
beta_frame = Frame(width="500", height="680")
beta_frame.pack()
holder = ScrolledWindow(beta_frame, width=500, height=680)
holder.pack()
alpha_frame = holder.window
I would like to position this scrollbar at the very bottom every time something new is put on the screen (which would obviously be added to the bottom The only things I'm adding to the screen are labels and buttons), though I'm unsure how to do this and I've searched everywhere. All I came up with is the method see, which I am unsure if it is even applicable in this instance. Any help would be appreciated.
.see() is the normal way to get Tkinter to auto-scroll to a given position, but that method only exists on the widgets that have built-in support for scrolling - Listbox, Canvas, Text, and Entry. The Tix ScrolledWindow makes an ordinary Frame scrollable, so no such method will exist.
It appears that this line of code will do what you want:
holder.tk.eval(holder.vsb['command'] + " moveto 1.0")
vsb is the vertical scrollbar component of the ScrolledWindow, 'command' is the scrollbar configuration option that specifies a callback to invoke when the position is changed. This will refer to something deep inside Tix, but we don't care exactly what it is; we just invoke it with the same parameters that the scrollbar itself would, if being moved to the very end.
My problem is this. I create a tkinter widget and later down the road I create a new frame that I want to add this widget to. When I call .grid() on the widget the widget is placed on the first frame, not the newer one that I want it to be on.
By default a widget is managed by its parent. If you don't want that, use the parameter in_ when calling pack, place or grid.
For example:
self.f1 = tk.Frame(...)
self.label = tk.Label(self.f1, ...)
self.label.pack(...)
...
self.f2 = tk.Frame(...)
self.label.pack(in_=self.f2, ...)
However, if you find yourself doing this a lot, you're probably doing something wrong. This is almost never necessary in most tkinter applications.
I have a canvas (for ttk.Frame not having xview,yview methods) holding frames inside of it, which I want to browse horizontally, as they are in the same row. Found some tutorials, and while they were dealing with different combination of widgets, I followed them, and tried to apply them to my problem, but with no success. I do see a scrollbar, but it doesn't do or respond to anything.
class App:
def __init__(self,db):
self.db = db
self.root = tkinter.Tk()
self.masterframe = ttk.Frame(self.root)
self.masterframe.grid()
self.mastercanvas = tkinter.Canvas(self.masterframe)
self.mastercanvas.grid()
self.scrollbar = ttk.Scrollbar(self.masterframe,orient="horizontal",
command = self.mastercanvas.xview)
self.scrollbar.grid()
self.mastercanvas.configure(xscrollcommand=self.scrollbar.set)
for i,e in enumerate(self.db.elements):
xf = XFrame(self,e)
xf.grid(row=0,column=i,sticky="n")
Edit:
class XFrame:
def __init__(self,app,x):
self.app = app
self.x = x
self.frame = ttk.Frame(self.app.mastercanvas)
self.set_up() # this sets frame's padding and populates it with widgets
Now, where ever I paste two lines of code here suggested* - at the end of the first init definition, or at the end of the second init definition - nothing new happens. I see my frames appearing as I intended them to appear - 3 of them. Part of the 4th. And an unfunctional scrollbar.
*
self.update_idletasks() # using self.root in first, self.app.root in second variant
self.mastercanvas.configure(scrollregion=self.mastercanvas.bbox("all"))
# in second variant reffered to as self.app.mastercanvas ...
You've got to configure the scrollregion attribute of the canvas so that it knows how much of the virtual canvas you want to scroll. This should do it:
# create everything that will be inside the canvas
...
# next, cause the window to be drawn, so the frame will auto-size
self.update_idletasks()
# now, tell the canvas to scroll everything that is inside it
self.mastercanvas.configure(scrollregion=self.mastercanvas.bbox("all"))
That being said, there's nothing in your canvas to be scrolled, and I'm not entirely sure what you were expecting to be in the canvas. If you are wanting to scroll through the instances of XFrame, they need to be children of some other frame, and that other frame needs to be an object on the canvas.
Im making a simplish widget that can act as a container for other widgets. One of the features of the widget is that you can expand/collapse it by clicking on it. My current method is basically looking up all child widgets of the layout and hiding them. I'm looking for any help on how to handle this properly - my current implementation has at least one serious caveat: that you can't add widgets while it's collapsed (they're added in an 'unhidden' state)
heres the setCollapsed method that is run when the widget is clicked
def collapsed(self):
return self._isCollapsed
def setCollapsed(self, collapseBool):
self._isCollapsed = collapseBool
if self.layout()!=None:
childWidgets = [self.layout().itemAt(i).widget() for i in range(self.layout().count())]
for w in childWidgets:
if isinstance(w,QtGui.QWidget):
w.setHidden(collapseBool)
if collapseBool:
self._cachedMargin = self.layout().margin()
self.layout().setMargin(0)
else:
self.layout().setMargin(self._cachedMargin)
Rather than hiding all child widgets individually, I would just hide a single parent item.