subprocess.call с използване на низ срещу използване на списък

Опитвам се да използвам rsync с subprocess.call. Странно, работи, ако предам subprocess.call низ, но няма да работи със списък (ала, документът на Python).

извикване на sp.call с низ:

In [23]: sp.call("rsync -av content/ writings_raw/", shell=True)
sending incremental file list

sent 6236 bytes  received 22 bytes  12516.00 bytes/sec
total size is 324710  speedup is 51.89
Out[23]: 0

извикване на sp.call със списък:

In [24]: sp.call(["rsync", "-av", "content/", "writings_raw/"], shell=True)
rsync  version 3.0.9  protocol version 30
Copyright (C) 1996-2011 by Andrew Tridgell, Wayne Davison, and others.
Web site: http://rsync.samba.org/
Capabilities:
    64-bit files, 64-bit inums, 32-bit timestamps, 64-bit long ints,
    socketpairs, hardlinks, symlinks, IPv6, batchfiles, inplace,
    append, ACLs, xattrs, iconv, symtimes

rsync comes with ABSOLUTELY NO WARRANTY.  This is free software, and you
are welcome to redistribute it under certain conditions.  See the GNU
General Public Licence for details.

rsync is a file transfer program capable of efficient remote update
via a fast differencing algorithm.

Usage: rsync [OPTION]... SRC [SRC]... DEST
  or   rsync [OPTION]... SRC [SRC]... [USER@]HOST:DEST
  or   rsync [OPTION]... SRC [SRC]... [USER@]HOST::DEST
  or   rsync [OPTION]... SRC [SRC]... rsync://[USER@]HOST[:PORT]/DEST
  or   rsync [OPTION]... [USER@]HOST:SRC [DEST]
  or   rsync [OPTION]... [USER@]HOST::SRC [DEST]
  or   rsync [OPTION]... rsync://[USER@]HOST[:PORT]/SRC [DEST]
The ':' usages connect via remote shell, while '::' & 'rsync://' usages connect
to an rsync daemon, and require SRC or DEST to start with a module name.

Options
 -v, --verbose               increase verbosity
 -q, --quiet                 suppress non-error messages
     --no-motd               suppress daemon-mode MOTD (see manpage caveat)
... snipped....
                             repeated: --filter='- .rsync-filter'
     --exclude=PATTERN       exclude files matching PATTERN
     --blocking-io           use blocking I/O for the remote shell
 -4, --ipv4                  prefer IPv4
 -6, --ipv6                  prefer IPv6
     --version               print version number
(-h) --help                  show this help (-h is --help only if used alone)
...snipped ...
rsync error: syntax or usage error (code 1) at main.c(1438) [client=3.0.9]
Out[24]: 1

Какво не е наред с начина, по който използвам списъка? Как бихте го поправили? Имам нужда от списъка, защото бих искал да използвам променливи. Разбира се, че мога да използвам:

  sp.call("rsync -av "+Orig+" "+Dest, shell=True)    

Но бих искал да разбера как subprocess разбира списъци срещу низове.

настройка на shell=False и списък:

In [36]: sp.call(['rsync', '-av', ORIG, DEST], shell=False)
sending incremental file list

sent 6253 bytes  received 23 bytes  12552.00 bytes/sec
total size is 324710  speedup is 51.74
Out[36]: 0

настройка на shell=False и низ

In [38]: sp.call("rsync -av"+" "+ORIG+" "+DEST, shell=False)
---------------------------------------------------------------------------
OSError                                   Traceback (most recent call last)
<ipython-input-38-0d366d3ef8ce> in <module>()
----> 1 sp.call("rsync -av"+" "+ORIG+" "+DEST, shell=False)

/usr/lib/python2.7/subprocess.pyc in call(*popenargs, **kwargs)
    491     retcode = call(["ls", "-l"])
    492     """
--> 493     return Popen(*popenargs, **kwargs).wait()
    494 
    495 

/usr/lib/python2.7/subprocess.pyc in __init__(self, args, bufsize, executable, stdin, stdout, stderr, preexec_fn, close_fds, shell, cwd, env, universal_newlines, startupinfo, creationflags)
    677                             p2cread, p2cwrite,
    678                             c2pread, c2pwrite,
--> 679                             errread, errwrite)
    680 
    681         if mswindows:

/usr/lib/python2.7/subprocess.pyc in _execute_child(self, args, executable, preexec_fn, close_fds, cwd, env, universal_newlines, startupinfo, creationflags, shell, p2cread, p2cwrite, c2pread, c2pwrite, errread, errwrite)
   1257                     if fd is not None:
   1258                         os.close(fd)
-> 1259                 raise child_exception
   1260 
   1261 

OSError: [Errno 2] No such file or directory