SB Tkinter Standard Dialog Boxes

Section 15.2 Tkinter Standard Dialog Boxes

Subsection 15.2.1 Introduction

There are many common programming tasks that can be performed using pre-defined GUI dialog boxes. The following discussion describes these dialog boxes and provides some simple examples. You can refer to the Python documentation for additional optional parameters.

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Subsection 15.2.2 Messages

A messagebox can display information to a user. There are three variations on these dialog boxes based on the type of message you want to display. The functions’ first parameter gives a name for the dialog box which is displayed in the window’s header. The second parameter is the text of the message. The functions return a string which is typically ignored.

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from tkinter import messagebox

messagebox.showinfo("Information","Informative message")
messagebox.showerror("Error", "Error message")
messagebox.showwarning("Warning","Warning message")

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Subsection 15.2.3 Yes/No Questions

The tkinter messagebox object also allows you to ask a user simple yes/no type questions and varies the button names based on the type of question. These functions are:

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from tkinter import messagebox

answer = messagebox.askokcancel("Question","Do you want to open this file?")
answer = messagebox.askretrycancel("Question", "Do you want to try that again?")
answer = messagebox.askyesno("Question","Do you like Python?")
answer = messagebox.askyesnocancel("Question", "Continue playing?")

The return value is a Boolean, True or False, answer to the question. If “cancel” is an option and the user selects the “cancel” button, None is returned.

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Subsection 15.2.4 Single Value Data Entry

If you want to ask the user for a single data value, either a string, integer, or floating point value, you can use a simpledialog object. A user can enter the requested value and hit “OK”, which will return the entered value. If the user hits “Cancel,” then None is returned.

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import tkinter as tk
from tkinter import simpledialog

application_window = tk.Tk()

answer = simpledialog.askstring("Input", "What is your first name?",
                                parent=application_window)
if answer is not None:
    print("Your first name is ", answer)
else:
    print("You don't have a first name?")

answer = simpledialog.askinteger("Input", "What is your age?",
                                 parent=application_window,
                                 minvalue=0, maxvalue=100)
if answer is not None:
    print("Your age is ", answer)
else:
    print("You don't have an age?")

answer = simpledialog.askfloat("Input", "What is your salary?",
                               parent=application_window,
                               minvalue=0.0, maxvalue=100000.0)
if answer is not None:
    print("Your salary is ", answer)
else:
    print("You don't have a salary?")

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Subsection 15.2.5 File Chooser

A common task is to select the names of folders and files on a storage device. This can be accomplished using a filedialog object. Note that these commands do not save or load a file. They simply allow a user to select a file. Once you have the file name, you can open, process, and close the file using appropriate Python code. These dialog boxes always return you a “fully qualified file name” that includes a full path to the file. Also note that if a user is allowed to select multiple files, the return value is a tuple that contains all of the selected files. If a user cancels the dialog box, the returned value is an empty string.

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import tkinter as tk
from tkinter import filedialog
import os

application_window = tk.Tk()

# Build a list of tuples for each file type the file dialog should display
my_filetypes = [('all files', '.*'), ('text files', '.txt')]

# Ask the user to select a folder.
answer = filedialog.askdirectory(parent=application_window,
                                 initialdir=os.getcwd(),
                                 title="Please select a folder:")

# Ask the user to select a single file name.
answer = filedialog.askopenfilename(parent=application_window,
                                    initialdir=os.getcwd(),
                                    title="Please select a file:",
                                    filetypes=my_filetypes)

# Ask the user to select a one or more file names.
answer = filedialog.askopenfilenames(parent=application_window,
                                     initialdir=os.getcwd(),
                                     title="Please select one or more files:",
                                     filetypes=my_filetypes)

# Ask the user to select a single file name for saving.
answer = filedialog.asksaveasfilename(parent=application_window,
                                      initialdir=os.getcwd(),
                                      title="Please select a file name for saving:",
                                      filetypes=my_filetypes)

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Subsection 15.2.6 Color Chooser

Tkinter includes a nice dialog box for choosing colors. You provide it with a parent window and an initial color, and it returns a color in two different specifications: 1) a RGB value as a tuple, such as (255, 0, 0) which represents red, and 2) a hexadecimal string used in web pages, such as "#FF0000" which also represents red. If the user cancels the operation, the return values are None and None.

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from tkinter import colorchooser

rgb_color, web_color = colorchooser.askcolor(parent=application_window,
                                             initialcolor=(255, 0, 0))

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