Collapse labels if empty

Question

I have three labels that are directly under eachother (see image). I'd like the labels to be collapsed when they're empty.

In the case of the image, the second label is empty. I'd like the third label to be placed on the location of the second label.

In WPF (.NET) this would be done via:

<Style TargetType="TextBlock">
        <Style.Triggers>
            <Trigger Property="Text" Value="">
                <Setter Property="Visibility" Value="Collapsed" />
            </Trigger>
        </Style.Triggers>
</Style>

The simplified code of the picture below is as such:

import customtkinter as ctk

gui = ctk.CTk()

status = ctk.StringVar(value="status_test")
warning = ctk.StringVar(value="")
error = ctk.StringVar(value="error_test")

ctk.CTkLabel(gui, textvariable=status, text_color="grey", wraplength=gui.winfo_vrootwidth()).pack()
ctk.CTkLabel(gui, textvariable=warning, text_color="yellow", wraplength=gui.winfo_vrootwidth()).pack()
ctk.CTkLabel(gui, textvariable=error, text_color="red", wraplength=gui.winfo_vrootwidth()).pack()

gui.mainloop()

Image of UI

make sure you dont set visibility of the control anywhere else — Denis Schaf
– Denis Schaf, Commented Sep 10, 2024 at 11:21

Bryan Oakley · Accepted Answer · 2024-09-09 19:01:47Z

1

The normal way to do this is to is to call pack_forget when the label is empty, given that you're using pack.

This requires that you separate the creation of the labels from the layout of the labels so that you can reference them individually.

Here's an example:

import customtkinter as ctk

gui = ctk.CTk()

status = ctk.StringVar(value="status_test")
warning = ctk.StringVar(value="warning_test")
error = ctk.StringVar(value="error_test")

status_label = ctk.CTkLabel(gui, textvariable=status, text_color="grey", wraplength=gui.winfo_vrootwidth())
warning_label = ctk.CTkLabel(gui, textvariable=warning, text_color="yellow", wraplength=gui.winfo_vrootwidth())
error_label = ctk.CTkLabel(gui, textvariable=error, text_color="red", wraplength=gui.winfo_vrootwidth())

status_label.pack()
warning_label.pack()
error_label.pack()


def add_warning(message):
    if message == "":
        warning_label.pack_forget()
    else:
        warning_label.pack(after=status_label)
        warning.set(message)

b1 = ctk.CTkButton(gui, text="Add warning", command=lambda: add_warning("Warning!"))
b2 = ctk.CTkButton(gui, text="Remove warning", command=lambda: add_warning(""))
b1.pack(side="bottom")
b2.pack(side="bottom")

gui.mainloop()

answered Sep 9, 2024 at 19:01

Bryan Oakley

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3 Comments

Ulas Over a year ago

Would it also be possible to add this feature to the label itself, by for instance inheriting from it. I assume the Label gives some sort of callback function to the textvariable to update itself. Would it be possible to amend this callback function?

Bryan Oakley Over a year ago

@Ulas: you can add a trace on the variable which can call a function whenever the variable changes.

Ulas Over a year ago

That would work. Thank you!

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