OSError: [Errno 2] No such file or directory while using python subprocess in Django

I am trying to run a program to make some system calls inside Python code using subprocess.call() which throws the following error:

Traceback (most recent call last):
      File "<console>", line 1, in <module>
      File "/usr/lib/python2.7/subprocess.py", line 493, in call
      return Popen(*popenargs, **kwargs).wait()
      File "/usr/lib/python2.7/subprocess.py", line 679, in __init__
errread, errwrite)
      File "/usr/lib/python2.7/subprocess.py", line 1249, in _execute_child
      raise child_exception
      OSError: [Errno 2] No such file or directory

My actual Python code is as follows:

url = "/media/videos/3cf02324-43e5-4996-bbdf-6377df448ae4.mp4"
real_path = "/home/chanceapp/webapps/chanceapp/chanceapp"+url
fake_crop_path = "/home/chanceapp/webapps/chanceapp/chanceapp/fake1"+url
fake_rotate_path = "/home/chanceapp/webapps/chanceapp.chanceapp/fake2"+url
crop = "ffmpeg -i %s -vf "%(real_path)+"crop=400:400:0:0 "+ "-strict -2 %s"%(fake_crop_path)
rotate = "ffmpeg -i %s -vf "%(fake_crop_path)+"transpose=1 "+"%s"%(fake_rotate_path)
move_rotated = "mv"+" %s"%(fake_rotate_path)+" %s"%(real_path)
delete_cropped = "rm "+"%s"%(fake_crop_path)
#system calls:
subprocess.call(crop)

Can I get some relevant advice on how to solve this?

Use shell=True if you're passing a string to subprocess.call.

From docs:

If passing a single string, either shell must be True or else the string must simply name the program to be executed without specifying any arguments.

subprocess.call(crop, shell=True)

or:

import shlex
subprocess.call(shlex.split(crop))

No such file or directory can be also raised if you are trying to put a file argument to Popen with double-quotes.

For example:

call_args = ['mv', '"path/to/file with spaces.txt"', 'somewhere']

In this case, you need to remove double-quotes.

call_args = ['mv', 'path/to/file with spaces.txt', 'somewhere']

Can't upvote so I'll repost @jfs comment cause I think it should be more visible.

@AnneTheAgile: shell=True is not required. Moreover you should not use it unless it is necessary (see @ valid's comment). You should pass each command-line argument as a separate list item instead e.g., use ['command', 'arg 1', 'arg 2'] instead of "command 'arg 1' 'arg 2'". – jfs Mar 3 '15 at 10:02