merge .webm (Audio) file and a .mp4 (Video) file

merge_webmp4.py

# https://stackoverflow.com/a/35939357/3362993

import os
import glob
import subprocess

flist = sorted(glob.glob("*.webm") + glob.glob("*.mp4"))
pairs_index = [(x, x + 2) for x in range(0, len(flist), 2)]
flist_pairs = [flist[pairs_index[i][0]:pairs_index[i][1]] for i in range(0, int(len(flist)/2))]

def merge(audio, video):    
    stem = os.path.splitext(audio)[0]
    outpath = stem + ".avi"

    if not os.path.exists(outpath):
        shell_cmd = "ffmpeg -i " + audio + " -i " + video + " -acodec copy -vcodec copy " + outpath
        print(shell_cmd)
        subprocess.call(shell_cmd, shell=True)
    return None

for pair in flist_pairs:
    merge(pair[1], pair[0])