使用元组单击tkinter中的值更改按钮上的标签文本

Question

I have a list of strings sorted in a tuple like this:

values = ('1.Python','2.Ruby','3.PHP','4.Perl','5.JavaScript')

My simple code is:

from tkinter import *

root = Tk()
values = ('1.Python','2.Ruby','3.PHP','4.Perl','5.JavaScript')

ru = Button(root,
            text="Next",
            )
ru.grid(column=0,row=0)

lab = Label(root,
            text=values[0])
lab.grid(column=1,row=0)

ru2 = Button(root,
             text="Previous"
             )
ru2.grid(column=2,row=0)

root.mainloop()

I have two tkinter buttons "next" and "previous", the text value of the Label is directly taken from the tuple ( text=value[0] ), however I would want to know how to show the next string from the tuple when the next button is pressed, and how to change it to the previous values when the "previous" button is pressed. I know it can be done using for-loop but I cannot figure out how to implement that. I am new to python.

Answer 1

Use Button(..., command=callback) to assign function which will change text in label lab["text"] = "new text"

callback means function name without ()

You will have to use global inside function to inform function to assign current += 1 to external variable, not search local one.

import tkinter as tk

# --- functions ---

def set_next():
    global current

    if current < len(values)-1:
        current += 1
        lab["text"] = values[current]

def set_prev():
    global current

    if current > 0:
        current -= 1
        lab["text"] = values[current]

# --- main ---

values = ('1.Python','2.Ruby','3.PHP','4.Perl','5.JavaScript')
current = 0

root = tk.Tk()

ru = tk.Button(root, text="Next", command=set_next)
ru.grid(column=0, row=0)

lab = tk.Label(root, text=values[current])
lab.grid(column=1, row=0)

ru2 = tk.Button(root, text="Previous", command=set_prev)
ru2.grid(column=2, row=0)

root.mainloop()

---

BTW: if Next has to show first element after last one

def set_next():
    global current

    current = (current + 1) % len(values)
    lab["text"] = values[current]

def set_prev():
    global current

    current = (current - 1) % len(values)
    lab["text"] = values[current]