I have a data file with chemical names (one name per line) and want to load that into a Tkinter GUI listbox and then be able to select it by clicking on the line. Need some help.

I had to fiddle with this for a while to get it to go. The scrollbar is a little hairy with Tkinter. Here is an example how to do this ...

# loading a Tkinter listbox with data and selecting a data line

from Tkinter import *

def get_list(event):
    """
    function to read the listbox selection
    and put the result in a label
    """
    # get line index tuple
    sel = listbox1.curselection()
    # get the text
    seltext = listbox1.get(int(sel[0]))
    label1.config(text=seltext)

# 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()
# create the listbox (note that size is in characters)
listbox1 = Listbox(root, width=50, height=6)
listbox1.grid(row=0, column=0)

# create a vertical scrollbar to the right of the listbox
yscroll = Scrollbar(command=listbox1.yview, orient=VERTICAL)
yscroll.grid(row=0, column=1, sticky=N+S)
listbox1.configure(yscrollcommand=yscroll.set)

# label to display selection
label1 = Label(root, text='Click on an item in the list')
label1.grid(row=1, column=0)

# load the listbox with data
for item in chem_list:
    listbox1.insert(END, item)

# left mouse click on a list item to display selection
listbox1.bind('<ButtonRelease-1>', get_list)

root.mainloop()

Oh thank you, that will be a good start into my next project. Is there a way to sort the items in a listbox?

In your case it would be easy to have a sorted listbox by simply loading it with a sorted list. So, replace the lines ...

# load the listbox with data
for item in chem_list:
    listbox1.insert(END, item)

... with ...

# load the listbox with data, sorted case insensitive
for item in sorted(chem_list, key=str.lower):
    listbox1.insert(END, item)

Rather than putting your selected line into Label, put it into Entry. Now you can edit it. Bind the Entry to double mouse click to load it back into Listbox at the index sel[0] you have.

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