Python help: Globally defined item keeps yielding not defined error

Question

PSA: Python learner (30 days and counting).
I am trying to create a python script which creates a playlist of videos which are randomly selected from given folder/sub-folder. When I run it, I get a "’selected_files’ is not defined" error in line 40 (in the "# create a VLC playlist in select folder" section) of my script, when I have clearly defined it globally…I think. Welcome the assist.

import os
import random
    
def find_files(folder, extensions):
    files = []
    for root, dirs, filenames in os.walk(folder):
        for filename in filenames:
            if any(filename.endswith(ext) for ext in extensions):
                files.append(os.path.join(root, filename))
    return files

def main():
    global selected_files
    # specify the folders to search and the file extensions to search for
    folders = [r"pathtoshow1", r"pathtoshow2", r"pathtoshow3", r"pathtoshow4"]
        
    extensions = (".mp4", ".avi", ".mkv")

    selected_files = []
    for folder in folders:
        files = find_files(folder, extensions)
        if files:
            selected_files.append(random.choice(files))
        else:
            print(f"No files found in {folder}.")
    if not selected_files:
        print("No files found.")
        return
    
# create a VLC playlist in select folder
playlist_folder = r"pathwhereplaylistissaved"
if not os.path.exists(playlist_folder):
    os.makedirs(playlist_folder)
playlist_file = os.path.join(playlist_folder, "PMTV.xspf")
with open(playlist_file, "w", encoding='utf8') as f:
    f.write('<?xml version="1.0" encoding="UTF-8"?>n')
    f.write('<playlist xmlns="http://xspf.org/ns/0/" xmlns_vlc="http://www.videolan.org/vlc/playlist/ns/0/" version="1">n')
    f.write('t<title></title>n')
    f.write('t<trackList>n')
    for file in selected_files:
        f.write('tt<track>n')
        f.write(f'ttt<location>{file}</location>n')
        f.write('ttt<title></title>n')
        f.write('ttt<duration></duration>n')
        f.write('ttt<extension application="http://www.videolan.org/vlc/playlist/0">n')
        f.write('tttt<vlc:id></vlc:id>n')
        f.write('ttt</extension>n')
        f.write('tt</track>n')
    f.write('t</trackList>n')
    f.write('</playlist>n')
print(f"{len(selected_files)} files added to {playlist_file}")
    
if __name__ == "__main__":
    main()

Asked By: rustyshackleford_V

||

Source

Answer 1

As your script is loaded, the code at

# create a VLC playlist in select folder

… gets executed, BEFORE reaching main

And it barfs at you as selected_files has not been defined yet.
… so by inserting

selected_files=[]

you define it, and stop the barfing.

Now, beyond this you have a likely logic fault in this, as selected_files contains nothing as you enter the loop at for file in selected_files: – on line 40 – due to the fact that it has not been filled with items yet.

Answered By: Hannu

Answer 2

Thank you, Hannu and Chepner. Don’t have commenting privileges, yet (newbie on SuperUser) so I’ll post what I did as an answer.

I made two changes, which solved the riddle:

#1) Define folders in main ()
    def main():
     folders = folders = [pathtoshow1, pathtoshow2...yada...yada...yada...]

#2) Localize selected_files
    selected_files = []
        for folder in folders:
            files = find_files(folder, extensions)
            if files:
                selected_files.append(random.choice(files))

Answered By: user21168294

Python help: Globally defined item keeps yielding not defined error

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