@Alexis said:

cmdstr2 = """ffmpeg -i " + moviespec + " 2>&1 | sed -n 's/., (.) fp.*/\1/p'"""

Okay, I forgot to escape one of the backslashes in the sed string. The proper python-fu is:

cmdstr3 = "\"\"ffmpeg -i " + moviespec + " 2>&1 | sed -n 's/.*, \(.*\) fp.*/\\1/p'\"\""

...which properly returns the FPS of the movie file.

Thanks so much for getting me started on this! I'm converting my bash scripts to python and learning the language in the process!

[My editor changed the simple quotes into “smart” quotes for the posting, sorry.]

Anyway, the code below works to obtain the movie resolution. It returns the string “640x480” for the moviespec var I’m using:

cmdstr1 = "\"\"ffmpeg -i " + moviespec + " 2>&1 | sed -n 's/.*, \(.*\) [.*/\\1/p'\"\""
stdoutstr1 = subprocess.check_output(
    cmdstr1,
    shell=True, universal_newlines=True)

However, in translating the following bash line to obtain the frames/second:

fps=$(/opt/local/bin/ffmpeg -i $moviespec 2>&1 | sed -n "s/.*, \(.*\) fp.*/\1/p")

The above line, translated into pythonese, returns null:

cmdstr2 = "\"\"ffmpeg -i " + moviespec + " 2>&1 | sed -n 's/.*, \(.*\) fp.*/\1/p'\"\""
stdoutstr2 = subprocess.check_output(
    cmdstr2,
    shell=True, universal_newlines=True)

I can’t spot what my error might be here.

@Alexis said:

cmdstr2 = """ffmpeg -i " + moviespec + " 2>&1 | sed -n 's/., (.) fp.*/\1/p'"""

Okay, I forgot to escape one of the backslashes in the sed string. The proper python-fu is:

cmdstr3 = "\"\"ffmpeg -i " + moviespec + " 2>&1 | sed -n 's/.*, \(.*\) fp.*/\\1/p'\"\""

...which properly returns the FPS of the movie file.

Thanks so much for getting me started on this! I'm converting my bash scripts to python and learning the language in the process!

[My editor changed the simple quotes into “smart” quotes for the posting, sorry.]

Anyway, the code below works to obtain the movie resolution. It returns the string “640x480” for the moviespec var I’m using:

cmdstr1 = "\"\"ffmpeg -i " + moviespec + " 2>&1 | sed -n 's/.*, \(.*\) [.*/\\1/p'\"\""
stdoutstr1 = subprocess.check_output(
    cmdstr1,
    shell=True, universal_newlines=True)

However, in translating the following bash line to obtain the frames/second:

fps=$(/opt/local/bin/ffmpeg -i $moviespec 2>&1 | sed -n "s/.*, \(.*\) fp.*/\1/p")

The above line, translated into pythonese, returns null:

cmdstr2 = "\"\"ffmpeg -i " + moviespec + " 2>&1 | sed -n 's/.*, \(.*\) fp.*/\1/p'\"\""
stdoutstr2 = subprocess.check_output(
    cmdstr2,
    shell=True, universal_newlines=True)

I can’t spot what my error might be here.

Great examples! How about something more real-world?

I use the following bash command to obtain the resolution of a movie file:

/opt/local/bin/ffmpeg -i TEST.mp4 2>&1 | sed -n "s/.*, \(.*\) [.*/\1/p"

...and it returns a string like “640x480” for the movie’s resolution. Great!

Now, trying to do this in Python 3:

cmd = ‘/opt/local/bin/ffmpeg -i TEST.mp4 2>&1 | sed -n "s/.*, \(.*\) [.*/\1/p"’
ret = subprocess.getoutput(cmd)

Result: null string

subprocess.call(cmd, shell=True)

Result: null string

stdoutstr = subprocess.getoutput(cmd)
print("stdoutstr:” + stdoutstr.split()[0])

Result: null string

Surely, there MUST be a way!