Py Script for looping over files

[b0ng0]

I am fairly new to python and I was just wondering if someone could post some code that would allow me to loop over files in a directory and perform a video conversion (using ffmpeg) one by one (so as not to chew up my CPU).
I was trying with os.walk() and os.listdir() but my knowledge of python is pretty limited. Thanks for any help/code

[Soybean]

I don't know how to do this in Python, so I probably shouldn't be answering at all... But I just thought I'd mention that, even when I do learn Python, this is probably something I'd still use Perl for. The Perl syntax for looping over all files in the current directory is:

#!/usr/bin/perl

while(<*>)
{
  print "$_ \n";
}

Then, instead of printing the filenames, you just replace that line with whatever you want to do, where $_ is the variable for the filename.

If you're trying to run command-line programs on each file (I assume ffmpeg is something you run from the command-line?), you can use system

system("ffmpeg $_ ...");

[[h2o]]

import glob

mpgfiles = glob.glob("~/video/*.mpg")

for file in mpgfiles:
  system("ffmpeg %s ...." % file)

glob is your friend

[b0ng0]

Woo! Thanks.

Just one last thing - each file will obviously have a different name, so the ffmpeg command will be something like:

ffmpeg -i movie.avi convertedmovie.avi

If I put this into the system("ffmpeg %s ...." % file) do I use %s where the file name should be?

Thanks

[[h2o]]

The python syntax for string formatting is

mystring = "I am an %s from %s" % ("alien","Mars")

I guess what you want is something like:

import glob

avifiles = glob.glob("~/video/*.avi")

for file in avifiles:
  outfile = "converted_%s" % file  # a.avi becomes converted_a.avi
  command = "ffmpeg -i %s %s " % (file, outfile) # create command
  system(command) # Run command

[b0ng0]

Awesome-o, thanks for that. I'll give it a go when I get back from work

[b0ng0]

Traceback (most recent call last):
File "convert.py", line 8, in ?
system(command) # Run command
NameError: name 'system' is not defined

I got this when I tried to run it. Should I have defined system before, or am I missing a module?

[Nekiruhs]

your missing a module. just add to the top

from os import system

[pmasiar]

for file in avifiles:

if you use any decent editor with syntax highlighting, you would notice that file has special color - it is reserved keyword and cannot be used as name. try infile instead.

[Soybean]

if you use any decent editor with syntax highlighting, you would notice that file has special color - it is reserved keyword and cannot be used as name. try infile instead.

Well that's interesting... gedit does color it differently, but on the other hand, it works. If file is a reserved word, why doesn't it cause an error? If you open python in interactive mode, it seems like you can use "file" however you want. That's kind of weird, isn't it?