Working with a Tkinter Listbox (Python)

# load a Tkinter listbox with data lines from a file,
# sort data lines, select a data line, display the data line,
# edit the data line, update listbox with the edited data line
# add/delete a data line, save the updated listbox to a data file
# used a more modern import to give Tkinter items a namespace
# tested with Python24       vegaseat       16nov2006
 
import Tkinter as tk  # gives tk namespace

def add_item():
    """
    add the text in the Entry widget to the end of the listbox
    """
    listbox1.insert(tk.END, enter1.get())

def delete_item():
    """
    delete a selected line from the listbox
    """
    try:
        # get selected line index
        index = listbox1.curselection()[0]
        listbox1.delete(index)
    except IndexError:
        pass
 
def get_list(event):
    """
    function to read the listbox selection
    and put the result in an entry widget
    """
    # get selected line index
    index = listbox1.curselection()[0]
    # get the line's text
    seltext = listbox1.get(index)
    # delete previous text in enter1
    enter1.delete(0, 50)
    # now display the selected text
    enter1.insert(0, seltext)

def set_list(event):
    """
    insert an edited line from the entry widget
    back into the listbox
    """
    try:
        index = listbox1.curselection()[0]
        # delete old listbox line
        listbox1.delete(index)
    except IndexError:
        index = tk.END
    # insert edited item back into listbox1 at index
    listbox1.insert(index, enter1.get())

def sort_list():
    """
    function to sort listbox items case insensitive
    """
    temp_list = list(listbox1.get(0, tk.END))
    temp_list.sort(key=str.lower)
    # delete contents of present listbox
    listbox1.delete(0, tk.END)
    # load listbox with sorted data
    for item in temp_list:
        listbox1.insert(tk.END, item)

def save_list():
    """
    save the current listbox contents to a file
    """
    # get a list of listbox lines
    temp_list = list(listbox1.get(0, tk.END))
    # add a trailing newline char to each line
    temp_list = [chem + '\n' for chem in temp_list]
    # give the file a different name
    fout = open("chem_data2.txt", "w")
    fout.writelines(temp_list)
    fout.close()
 
# create the sample data file
str1 = """ethyl alcohol
ethanol
ethyl hydroxide
hydroxyethane
methyl hydroxymethane
ethoxy hydride
gin
bourbon
rum
schnaps
"""
fout = open("chem_data.txt", "w")
fout.write(str1)
fout.close()
 
# read the data file into a list
fin = open("chem_data.txt", "r")
chem_list = fin.readlines()
fin.close()
# strip the trailing newline char
chem_list = [chem.rstrip() for chem in chem_list]
 
root = tk.Tk()
root.title("Listbox Operations")
# create the listbox (note that size is in characters)
listbox1 = tk.Listbox(root, width=50, height=6)
listbox1.grid(row=0, column=0)
 
# create a vertical scrollbar to the right of the listbox
yscroll = tk.Scrollbar(command=listbox1.yview, orient=tk.VERTICAL)
yscroll.grid(row=0, column=1, sticky=tk.N+tk.S)
listbox1.configure(yscrollcommand=yscroll.set)
 
# use entry widget to display/edit selection
enter1 = tk.Entry(root, width=50, bg='yellow')
enter1.insert(0, 'Click on an item in the listbox')
enter1.grid(row=1, column=0)
# pressing the return key will update edited line
enter1.bind('<Return>', set_list)
# or double click left mouse button to update line
enter1.bind('<Double-1>', set_list)

# button to sort listbox
button1 = tk.Button(root, text='Sort the listbox    ', command=sort_list)
button1.grid(row=2, column=0, sticky=tk.W)

# button to save the listbox's data lines to a file
button2 = tk.Button(root, text='Save lines to file', command=save_list)
button2.grid(row=3, column=0, sticky=tk.W)

# button to add a line to the listbox
button3 = tk.Button(root, text='Add entry text to listbox', command=add_item)
button3.grid(row=2, column=0, sticky=tk.E)

# button to delete a line from listbox
button4 = tk.Button(root, text='Delete selected line     ', command=delete_item)
button4.grid(row=3, column=0, sticky=tk.E)

# load the listbox with data
for item in chem_list:
    listbox1.insert(tk.END, item)
 
# left mouse click on a list item to display selection
listbox1.bind('<ButtonRelease-1>', get_list)
 
root.mainloop()