Tkinter file selection dialog fails to pass selected file ending and append to file being saved

[elkym]

Bug report

Bug description:

import tkinter as tk
from tkinter import filedialog
import os

class FileDialogTest:
    def __init__(self, file_extensions):
        self.file_extensions = file_extensions
        self.selected_file_type = None

    def _format_file_extensions(self):
        return [(f"{ext} files", ext) for ext in self.file_extensions]

    def _get_file_type(self, file_path):
        _, ext = os.path.splitext(file_path)
        return ext

    def select_file_to_save(self, default_name="testfile"):
        root = tk.Tk()
        root.withdraw()
        file_path = filedialog.asksaveasfilename(
            title="Select a file to save",
            filetypes=self._format_file_extensions(),
            initialfile=default_name
        )
        if not file_path:
            raise FileNotFoundError("No file selected.")
        self.selected_file_type = self._get_file_type(file_path)
        if not self.selected_file_type:
            # Append the default extension based on the selected file type
            self.selected_file_type = self.file_extensions[0]  # Default to the first extension if none is selected
            file_path += self.selected_file_type
        return file_path, self.selected_file_type

# Define file extensions for testing
file_extensions = ['.txt', '.csv']

# Initialize FileDialogTest with file extensions
file_dialog_test = FileDialogTest(file_extensions)

# Test select_file_to_save method
try:
    file_path, selected_file_type = file_dialog_test.select_file_to_save()
    print(f"Selected file path: {file_path}")
    print(f"Selected file type: {selected_file_type}")
except FileNotFoundError as e:
    print(e)

CPython versions tested on:

3.11

Operating systems tested on:

Windows

[JeffersGlass]

What is the expected output here, and what are you seeing?

On both Python 3.11 and 3.14 (main), when I run this script and hit Save with the default file name, I see something like:

Selected file path: /home/jglass/Documents/cpython/testfile.txt
Selected file type: .txt

This is on ubuntu 22.04, for what it's worth.

[terryjreedy]

And specify what you enter enter into the dialog box and what button you hit, as Jeff did above.

The filedialog doc is a bit skimpy. I have a vague memory of having issues getting the behavior we want across OSes, with macOS being the hardest. IDLE directly uses the Open and SaveAs classes and their show methods, so I have no experience with the convenience function wrappers.

[elkym]

What is the expected output here, and what are you seeing?

On both Python 3.11 and 3.14 (main), when I run this script and hit Save with the default file name, I see something like:

Selected file path: /home/jglass/Documents/cpython/testfile.txt
Selected file type: .txt

This is on ubuntu 22.04, for what it's worth.

I suspect that @terryjreedy is right-- I'm guessing this is an OS issue, but I'm not seeing enough in the documentation as yet to be certain.

Printed output at my console:
Selected file path: C:/Users/~~/MarcTT-2025-Testing/testfile.txt
Selected file type: .txt

The script prints those messages for me just fine, but no file is getting created in the working directory.

The script doesn't actually save the file, unless I manually enter the file ending, '.txt'.

I've run into a similar issue in Windows before, in which if a file path lacked an ending, the file wouldn't get written. I'm not sure if this is the same.

Would you mind checking to see if your script actually created the file? @JeffersGlass

[JeffersGlass]

@elkym I will presently when I'm back at the correct computer... but I'm not seeing where in your example code the file would actually get written. You retrieve a file path and extension, print it out, but I don't see where your sample code is actually writing to the file. What am I missing?

On the windows laptop I am on now, it does not create the file with your code. However, if I add this to the end of your try block:

with open(file_path, "w+") as f:
    f.write("Hello, world!")

It successfully writes the correct filename, whether I type ".txt" into the file name box or not. (This on a Windows 10 laptop now.)

Are you saying that the code as written above, with no changes, actually writes to a file when you give it a name ending in "txt"? If so, what's in that file?

Edit: This tested with python 3.11.7, for what it's worth.

[elkym]

I'm wondering if I've pasted the wrong version of the code. I'll have to check when I get back to my computer. I'm missing the function somehow, as you pointed out.

[elkym]

Ok. So maybe I'm wrong about where the problem is. I got it working.
`import tkinter as tk
from tkinter import filedialog
import os

class FileDialogTest:
def init(self, file_extensions):
self.file_extensions = file_extensions
self.selected_file_type = None

def _format_file_extensions(self):
    return [(f"{ext} files", ext) for ext in self.file_extensions]

def _get_file_type(self, file_path):
    _, ext = os.path.splitext(file_path)
    return ext

def select_file_to_save(self, default_name="testfile"):
    root = tk.Tk()
    root.withdraw()
    file_path = filedialog.asksaveasfilename(
        title="Select a file to save",
        filetypes=self._format_file_extensions(),
        initialfile=default_name
    )
    if not file_path:
        raise FileNotFoundError("No file selected.")
    self.selected_file_type = self._get_file_type(file_path)
    if not self.selected_file_type:
        # Append the default extension based on the selected file type
        self.selected_file_type = self.file_extensions[0]  # Default to the first extension if none is selected
        file_path += self.selected_file_type
    return file_path, self.selected_file_type

Define file extensions for testing

file_extensions = ['.txt', '.csv']

Initialize FileDialogTest with file extensions

file_dialog_test = FileDialogTest(file_extensions)

Test select_file_to_save method

try:
file_path, selected_file_type = file_dialog_test.select_file_to_save()
print(f"Selected file path: {file_path}")
print(f"Selected file type: {selected_file_type}")

# Sample data to save
sample_data = ["Value 1", 123, "Another string", 456.78]

# Save the sample data to the selected file
with open(file_path, 'w') as f:
    for item in sample_data:
        f.write(f"{item}\n")

print(f"Data saved to {file_path}")

except FileNotFoundError as e:
print(e)`

But this was an attempt at a simplified version of another script, writing parquet and xlsx files-- I'll be looping back around to that.

It may be an issue with the to_parquet and/or xlsxwriter elements of that script. I may be back with a new post soon.