• Consider what happens if a user closes the "Load MP3" dialog without picking a file. In that case, filepath would get set to "". The label would not change, but should the user press the "Shred" button anyway, we would try to import a file called "" (since the filepath variable exists, we don't get that NameError) which would presumably not go terribly well
• I'm not sure why we write the chunks to temporary files only to read them again? It seems like it'd be simpler to do something like this:

glued_song = AudioSegment.empty()

for chunk in song[::1000]:
    glued_song += chunk

• Should you need to keep the temp files, I would advise using the tempfile module to create it in a more secure and portable manner, in a standard location
• You only seem to use mutagen to get the duration of the original track. Since pydub supports getting the duration of AudioSegments, (using song.duration_seconds), taking on a whole other dependency just for that seems unnecessary
• Instead of a global variable, it may be neater to have the currently selected file path be a property of the shredder class - you could set it like self.filepath = None in the __init__, and then access it as self.filepath in getfile and shred
• I do think allowing the user to pick the output file name might be a desirable feature
• Finally, I'm not a big fan of some of the variable names in use here:
  • shredder, as a class name, would typically be written like Shredder
  • btn and btn1 tells me very little about what those buttons are. load_button and shred_button, for example, would be more descriptive
  • Similarly, I have no clue what le means. I might go for something like path_label or selection_label instead
  • getfile is two words - get_file. Or perhaps select_file, or pick_file, to more clearly indicate a choice is being made
  • song is re-used for different purposes in the same method, which might get confusing
  • glue_it_back sounds like less like a thing and more like something you do - it's a fine name for a function, but for an object I'd prefer something like glued_song, or even just result

• Consider what happens if a user closes the "Load MP3" dialog without picking a file. In that case, filepath would get set to "". The label would not change, but should the user press the "Shred" button anyway, we would try to import a file called "" (since the filepath variable exists, we don't get that NameError) which would presumably not go terribly well
• I'm not sure why we write the chunks to temporary files only to read them again? It seems like it'd be simpler to do something like this:

glued_song = AudioSegment.empty()

for chunk in random.sample(song[::1000], song.duration_seconds):
    glued_song += chunk

• Should you need to keep the temp files, I would advise using the tempfile module to create it in a more secure and portable manner, in a standard location
• You only seem to use mutagen to get the duration of the original track. Since pydub supports getting the duration of AudioSegments, (using song.duration_seconds), taking on a whole other dependency just for that seems unnecessary
• Instead of a global variable, it may be neater to have the currently selected file path be a property of the shredder class - you could set it like self.filepath = None in the __init__, and then access it as self.filepath in getfile and shred
• I do think allowing the user to pick the output file name might be a desirable feature
• Finally, I'm not a big fan of some of the variable names in use here:
  • shredder, as a class name, would typically be written like Shredder
  • btn and btn1 tells me very little about what those buttons are. load_button and shred_button, for example, would be more descriptive
  • Similarly, I have no clue what le means. I might go for something like path_label or selection_label instead
  • getfile is two words - get_file. Or perhaps select_file, or pick_file, to more clearly indicate a choice is being made
  • song is re-used for different purposes in the same method, which might get confusing
  • glue_it_back sounds like less like a thing and more like something you do - it's a fine name for a function, but for an object I'd prefer something like glued_song, or even just result

• Consider what happens if a user closes the "Load MP3" dialog without picking a file. In that case, filepath would get set to "". The label would not change, but should the user press the "Shred" button anyway, we would try to import a file called "" (since the filepath variable exists, we don't get that NameError) which would presumably not go terribly well
• I'm not sure why we write the chunks to temporary files only to read them again? It seems like it'd be simpler to do something like this:

glued_song = AudioSegment.empty()

for chunk in song[::1000]:
    glued_song += chunk

• Should you need to keep the temp files, I would advise using the tempfile module to create it in a more secure and portable manner, in a standard location
• You only seem to use mutagen to get the duration of the original track. Since pydub supports getting the duration of AudioSegments, (using song.duration_seconds), taking on a whole other dependency just for that seems unnecessary
• Instead of a global variable, it may be neater to have the currently selected file path be a property of the shredder class
• I do think allowing the user to pick the output file name might be a desirable feature
• Finally, I'm not a big fan of some of the variable names in use here:
  • shredder, as a class name, would typically be written like Shredder
  • btn and btn1 tells me very little about what those buttons are. load_button and shred_button, for example, would be more descriptive
  • Similarly, I have no clue what le means. I might go for something like path_label or selection_label instead
  • getfile is two words - get_file. Or perhaps select_file, or pick_file, to more clearly indicate a choice is being made
  • song is re-used for different purposes in the same method, which might get confusing
  • glue_it_back sounds like less like a thing and more like something you do - it's a fine name for a function, but for an object I'd prefer something like glued_song, or even just result

• Consider what happens if a user closes the "Load MP3" dialog without picking a file. In that case, filepath would get set to "". The label would not change, but should the user press the "Shred" button anyway, we would try to import a file called "" (since the filepath variable exists, we don't get that NameError) which would presumably not go terribly well
• I'm not sure why we write the chunks to temporary files only to read them again? It seems like it'd be simpler to do something like this:

glued_song = AudioSegment.empty()

for chunk in song[::1000]:
    glued_song += chunk

• Should you need to keep the temp files, I would advise using the tempfile module to create it in a more secure and portable manner, in a standard location
• You only seem to use mutagen to get the duration of the original track. Since pydub supports getting the duration of AudioSegments, (using song.duration_seconds), taking on a whole other dependency just for that seems unnecessary
• Instead of a global variable, it may be neater to have the currently selected file path be a property of the shredder class - you could set it like self.filepath = None in the __init__, and then access it as self.filepath in getfile and shred
• I do think allowing the user to pick the output file name might be a desirable feature
• Finally, I'm not a big fan of some of the variable names in use here:
  • shredder, as a class name, would typically be written like Shredder
  • btn and btn1 tells me very little about what those buttons are. load_button and shred_button, for example, would be more descriptive
  • Similarly, I have no clue what le means. I might go for something like path_label or selection_label instead
  • getfile is two words - get_file. Or perhaps select_file, or pick_file, to more clearly indicate a choice is being made
  • song is re-used for different purposes in the same method, which might get confusing
  • glue_it_back sounds like less like a thing and more like something you do - it's a fine name for a function, but for an object I'd prefer something like glued_song, or even just result