Python: "list index out of range"

Question

Issues:

1. What makes the code snippet below? He’s making a mistake.
2. How can I identify and correct this mistake?

verificar = self.tree.column(titulos_listbox[ix], width=None)

When running the code, displays the following error message:

Indexerror: list index out of range

If I remove all part of the code below, the program runs normally.

        for ix, val in enumerate(item):
            col_w = tkFont.Font().measure(val)
            verificar = self.tree.column(titulos_listbox[ix], width=None)
            if verificar<col_w:
                self.tree.column(titulos_listbox[ix], width=col_w)

The result will be the following image:

'''
Here the TreeView widget is configured as a multi-column listbox
with adjustable column width and column-header-click sorting.
'''
try:
    import Tkinter as tk
    import tkFont
    import ttk
except ImportError:  # Python 3
    import tkinter as tk
    import tkinter.font as tkFont
    import tkinter.ttk as ttk

class MultiColumnListbox(object):
    """use a ttk.TreeView as a multicolumn ListBox"""

    def __init__(self):
        self.tree = None
        self._setup_widgets()
        self._build_tree()

    def _setup_widgets(self):
        # s = "BANDO DE DADOS"
        #
        # msg = ttk.Label(wraplength="4i", justify="left", anchor="n",
        #     padding=(10, 2, 10, 6), text=s)
        # msg.pack(fill='x')
        container = ttk.Frame()
        # container.pack(fill='both', expand=True)
        container.place(x=5, y=5, width=1170)

        # create a treeview with dual scrollbars
        self.tree = ttk.Treeview(columns=titulos_listbox, show="headings")
        vsb = ttk.Scrollbar(orient="vertical",
            command=self.tree.yview)
        hsb = ttk.Scrollbar(orient="horizontal",
            command=self.tree.xview)
        self.tree.configure(yscrollcommand=vsb.set,
            xscrollcommand=hsb.set)
        self.tree.grid(column=0, row=0, sticky='nsew', in_=container)
        vsb.grid(column=1, row=0, sticky='ns', in_=container)
        hsb.grid(column=0, row=1, sticky='ew', in_=container)
        container.grid_columnconfigure(0, weight=1)
        container.grid_rowconfigure(0, weight=1)

    def _build_tree(self):
        for col in titulos_listbox:
            self.tree.heading(col, text=col.title(),
                command=lambda c=col: sortby(self.tree, c, 0))
            # adjust the column's width to the header string
            self.tree.column(col,
                width=tkFont.Font().measure(col.title()))

        for item in banco_dados:
            self.tree.insert('', 'end', values=item)
            # adjust column's width if necessary to fit each value

            for ix, val in enumerate(item):
                col_w = tkFont.Font().measure(val)
                verificar = self.tree.column(titulos_listbox[ix], width=None)
                if verificar<col_w:
                    self.tree.column(titulos_listbox[ix], width=col_w)

def sortby(tree, col, descending):
    """sort tree contents when a column header is clicked on"""
    # grab values to sort
    data = [(tree.set(child, col), child) \
        for child in tree.get_children('')]
    # if the data to be sorted is numeric change to float
    #data =  change_numeric(data)
    # now sort the data in place
    data.sort(reverse=descending)
    for ix, item in enumerate(data):
        tree.move(item[1], '', ix)
    # switch the heading so it will sort in the opposite direction
    tree.heading(col, command=lambda col=col: sortby(tree, col, \
        int(not descending)))

# the test data ...

titulos_listbox = ['Data', 'Código', 'Item', 'Quantidade', 'Custo unitário', 'Custo total']
banco_dados = [
    ('01/01/2019', 123, 'teste1', 1, 10.0, 100.0, 'observação1'),
    ('02/01/2019', 456, 'teste2', 2, 20.0, 200.0, 'observação2'),
    ('03/01/2019', 789, 'teste3', 3, 30.0, 300.0, 'observação3')]



if __name__ == '__main__':
    root = tk.Tk()
    root.title("Multicolumn Treeview/Listbox")
    root["bg"] = "LightSteelBlue"
    root.geometry('1180x650+5+40')
    listbox = MultiColumnListbox()
    root.mainloop()

MultiColumnListbox()

Answer 1

In the verificar = self.tree.column(titulos_listbox[ix], width=None) the program passes column by column searching which of them has width equal to nothing to, in the if next, assign the width of col_w.

[...]
if verificar<col_w:
                    self.tree.column(titulos_listbox[ix], width=col_w)

The error of index out of range very likely it is happening because you have 6 columns analyzed and there are only 5 of them declared, for example. You’re referring to something that doesn’t exist.