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Kenny Barrera
Asked: 2020-09-28 14:21:58 +0800 CST 2020-09-28 14:21:58 +0800 CST

How do I add text to a Text widget in Tkinter?

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For the sake of simplicity, my "form" looks something like this:

import tkinter as tk

ventana = tk.Tk()

mensaje = tk.Text(ventana, background="white", width=165, height=25)
mensaje.config(state="disable")
mensaje.pack(padx=0, pady=125)

mensaje.insert(INSERT, "Hola Mundo")

ventana.mainloop()

I understand that I mensaje.insert(INSERT, "Hola Mundo")should add the required text to my widget, but I get this error:

File "search.py", line 5, in message.insert(INSERT, "Hello World") NameError: name 'INSERT' is not defined

What am I doing wrong?

python

1 Answers

  1. Best Answer

    INSERTis a variable defined inside the module tkinterand that has as value the string 'insert'. Actually, according to Python conventions it is a constant (identifier in capital letters should be treated as constants, keeping in mind that the concept of a constant does not exist in Python as such.)

    When belonging to the module tkinterand performing the import of the form, import tkinter as tkyou must indicate the namespace to which it belongs:

    mensaje.insert(tk.INSERT, "Hola Mundo")

    The confusion comes because much of the tkinter documentation ignores what PEPs and Python's own zen say about imports. It is very common to import in the form from tkinter import *, this is generally a bad practice, the only possible justification is that you want to overwrite tkinter widgets with ttk ones, and even then I don't like it :).

    from tkinter import *imports all globals into the current namespace, so it mensaje.insert(INSERT, "Hola Mundo")'s valid. The problem is that this can cause collisions with other imports or with our own variables, it populates the current namespace unnecessarily and we end up not clearly knowing where everything came from.

    The Zen of Python says:

    • Explicit better than implicit.
    • Namespaces are a good idea, let's do more of this.
    • Legibility counts.

    There's no point in throwing it all away to save us tk.(or std::in C++ and its using namespace std...). With tk.INSERTwe know who that variable belongs to and it never conflicts with other variables called INSERTin our own module or in other imports.

    Like the rest of constants such as N, NW, CENTER, etc, they can be substituted in the methods where they are used, replacing them with their value

    mensaje.insert("insert", "Hola Mundo")

    The method tkinter.Text.insertreceives as its first argument the index where the text is going to be inserted, the second is the text itself and the third is a tuple with the labels associated with that text and which is optional. The index can be specified in many ways ( see documentation ). With tk.INSERTwe indicate that the index where it should be inserted is the current position of the cursor in the widget Text.

    Finally, indicate that text cannot be inserted either through code or through standard input if it Texthas the status as "disabled".

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