Python + ffmpeg TypeError: not all arguments converted during string formatting

Question

I'm sending a file to a function in python, and trying to save the results to a variable, but I keep getting that error.

I've looked over the other answers but nothing seems to fit. Any help is appreciated:

def ffmpegLUFS(fileName):
    subprocess.Popen("ffmpeg -i %s -filter_complex ebur128 -f null - 2>&1 | grep -n '.*' | grep -A 5 'size' | grep 'I:' | cut -d ':' -f3-" % tuple(map(pipes.quote, sys.argv[1])),stdout=subprocess.PIPE,shell=True).communicate()[0]
    return

Traceback (most recent call last):
  File "/Volumes/videos/videos/DROP_BIN/CHRIS/POD_Workflow_Files/WebContent_Audio.py", line 30, in <module>
    sourceLUFS = ffmpegLUFS(sys.argv[1])
  File "/Volumes/videos/videos/DROP_BIN/CHRIS/POD_Workflow_Files/WebContent_Audio.py", line 18, in ffmpegLUFS
    subprocess.Popen("ffmpeg -i %s -filter_complex ebur128 -f null - 2>&1 | grep -n '.*' | grep -A 5 'size' | grep 'I:' | cut -d ':' -f3-" % tuple(map(pipes.quote, fileName)),stdout=subprocess.PIPE,shell=True).communicate()[0]
TypeError: not all arguments converted during string formatting

Answer 1

I'm not sure what you're trying to achieve with this part of your code:

tuple(map(pipes.quote, sys.argv[1]))

The Python map function takes a function and an iterable and returns a list obtained by applying the function to each element of the iterable ^[1] . In your case, the iterable is a string, and the elements of the string are its characters, so the result of map(pipes.quote, sys.argv[1]) will be a list of characters from your string, quoted as necessary. For example, if sys.argv[1] is 10 characters long, map(pipes.quote, sys.argv[1]) will be a list of length 10.

I could only see one %s placeholder in your command-line string, so unless sys.argv[1] happens to contain only one character, you will encounter the 'not all arguments converted...' exception, because the number of %s placeholders in your string differs from the number of values you are attempting to put into the string.

As I see it, the simplest fix is to remove the calls to tuple and map and just use pipes.quote(sys.argv[1]) instead.

^[1] map() can actually take more than one iterable, but for simplicity I'm ignoring this. When given two arguments it behaves as I have described.