Pydub concatenate mp3 in a directory

Just sum as elements of a Python list:

sum(playlist_songs)

you can start with an empty sound like so:

combined = AudioSegment.empty()
for song in playlist_songs:
    combined += song

combined.export("/path/to/output.mp3", format="mp3")

or if you'd like to get a little fancy and use 5 second crossfades you'll have to pop the first song off the list

combined = playlist_songs[0]

for song in playlist_songs[1:]:
    combined = combined.append(song, crossfade=5000)

combined.export("/path/to/output.mp3", format="mp3")