"""A list box with add/replace/delete
operations."""

from Tkinter import *

class App:

    def __init__(self, parent):
        self.parent = parent
        self.create_widgets()

    def create_widgets(self):
        self.listbox1 = Listbox(
            self.parent,
            width=20, height=10,
            exportselection=0)
        self.listbox1.pack(
            expand=1, fill=BOTH)
        self.entry1 = Entry(
            self.parent)
        self.entry1.pack(fill=BOTH)
        self.b_add = Button(
            self.parent, text="add",
            command=self.add_it)
        self.b_add.pack()
        self.b_replace = Button(
            self.parent, text="replace",
            command=self.replace_it)
        self.b_replace.pack()
        self.b_delete = Button(
            self.parent, text="delete",
            command=self.delete_it)
        self.b_delete.pack()
        
        self.entry1.bind(
            '<Return>',
            self.replace_it)
        self.listbox1.bind(
            '<ButtonRelease-1>',
            self.select_it)

        self.listbox1.insert(
            0, 'Alabama','Alaska',
            'Arizona', 'etcetera')

    def select_it(self, event=None):
        index = self.getcurrent()
        if index >= 0:
            data = self.listbox1.get(index)
            self.entry1.delete(0, END)
            self.entry1.insert(END, data)
            self.entry1.select_range(0, END)
            self.entry1.focus_set()

    def add_it(self, event=None):
        data = self.entry1.get()
        self.entry1.select_range(0, END)
        self.listbox1.select_clear(0, END)
        self.listbox1.insert(END, data)

    def replace_it(self, event=None):
        data = self.entry1.get()
        self.entry1.select_range(0, END)
        index = self.getcurrent()
        if index >= 0:
            self.listbox1.delete(index)
        else:
            index = END
        self.listbox1.insert(index, data)
        self.listbox1.select_clear(0, END)
        if index != END:
            self.listbox1.select_set(index)

    def delete_it(self, event=None):
        index = self.getcurrent()
        if index >= 0:
            self.listbox1.delete(index)
            self.listbox1.select_set(index)

    def getcurrent(self):
        list = self.listbox1.curselection()
        if len(list) > 0:
            return list[0]
        else:
            return -1


# Boilerplate from here on...
if __name__ == '__main__':
    root = Tk()
    app = App(root)
    root.mainloop()