python tkinter treeview sort tree

Question

based on examples and Henry's help I have come up with the following code to sort the tree in a tkinter treeview, but it does not work. I do not get any errors but the tree is not sorted. Any help is appreciated.

def treeview_sort_column(tv, col, reverse):
 l = [(tv.set(k, col), k) for k in tv.get_children('')]
 l.sort(key=lambda t: int(t[0]), reverse=reverse)
 # ^^^^^^^^^^^^^^^^^^^^^^^
 for index, (val, k) in enumerate(l):
 tv.move(k, '', index)
 tv.heading(col,
 command=lambda: treeview_sort_column(tv, col, not reverse))
def SortTree():
 columns = ('#0',)
 for col in columns:
 tree.heading(col, text=col,
 command=lambda c=col: treeview_sort_column(tree, c, False))

• Henry Yik: Did you execute SortTree? You should get a _tkinter.TclError: Display column #0 cannot be set if you did when you do the sorting with the above code.
• ironfish: Hi, I do run SortTree (I have some print statements to make sure) and I do not get any errors if I use columns = ('#0',), if I use columns = ('#0') without a comma then I get _tkinter.TclError: Invalid column index #
• ironfish: I feel like I am guessing with this whole code because I cannot seem to find any documentation on this, and examples that I find, they sort other columns, not the tree. A tree item can have features such as text, tag, iid, etc and I am sure I need to specify which one to sort on, but I don't know how to. Any sample code would be appreciated.
• Henry Yik: I had shown a sample below to just sort on first column.

Answer 1

Since you are just adding the command to column #0, you don't have to put it in a loop.

from tkinter import ttk
import tkinter as tk
root = tk.Tk()
tree = ttk.Treeview(root,height=10)
tree.pack()
def treeview_sort_column(tv, col, reverse):
 l = [(tv.item(k)["text"], k) for k in tv.get_children()] #Display column #0 cannot be set
 l.sort(key=lambda t: t[0], reverse=reverse)
 for index, (val, k) in enumerate(l):
 tv.move(k, '', index)
 tv.heading(col, command=lambda: treeview_sort_column(tv, col, not reverse))
tree.heading("#0", command=lambda : treeview_sort_column(tree, "#0", False))
for i in range(10):
 tree.insert("",0,text=i)
root.mainloop()

• ironfish: Thanks again, it was very helpful! Unfortunately I do not have enough Reputation to upvote your answer....
• Henry Yik: If it helped, you can check it as the accepted answer.
• Zelphir Kaltstahl: For explanation: treeview.set can apparently not be called on column "#0". So instead of doing that, a different way of getting the value of the treeview items, according to which we want to sort the items. This is apparently done by treeview.item(item)["text"], avoiding the error.

Answer 2

As I wanted to sort by column values alphabetically on clicking the specific column header I made an addition to the function in the answer of @Henry Yik and wanted to post for people with the same question in the future.

def treeview_sort_column(tv, col, reverse):
 column_index = self.tree["columns"].index(col)
 l = [(str(tv.item(k)["values"][column_index]), k) for k in tv.get_children()]
 l.sort(key=lambda t: t[0], reverse=reverse)
 for index, (val, k) in enumerate(l):
 tv.move(k, '', index)
 
 tv.heading(col, command=lambda: treeview_sort_column(tv, col, not reverse))