Tk treeview column sort

This did not work in python3. Since the Variable was passed by reference, all lambdas ended up refering to the same, last, element in columns.

This did the trick for me:

for col in columns:
    treeview.heading(col, text=col, command=lambda _col=col: \
                     treeview_sort_column(treeview, _col, False))

patthoyts from #tcl pointed out that the TreeView Tk demo program had the sort functionality. Here's the Python equivalent of it:

def treeview_sort_column(tv, col, reverse):
    l = [(tv.set(k, col), k) for k in tv.get_children('')]
    l.sort(reverse=reverse)

    # rearrange items in sorted positions
    for index, (val, k) in enumerate(l):
        tv.move(k, '', index)

    # reverse sort next time
    tv.heading(col, command=lambda: \
               treeview_sort_column(tv, col, not reverse))

[...]
columns = ('name', 'age')
treeview = ttk.TreeView(root, columns=columns, show='headings')
for col in columns:
    treeview.heading(col, text=col, command=lambda: \
                     treeview_sort_column(treeview, col, False))
[...]