try:
    [zenity command here]
except subprocess.CalledProsessError:
    do this
else:
    do that

p = subprocess.Popen(cmd, shell=True, stdout=subprocess.PIPE)

subprocess.check_output()

subprocess.Popen()

subprocess.call()

shell=True

  File "/usr/lib/python2.7/subprocess.py", line 711, in __init__
    errread, errwrite)
  File "/usr/lib/python2.7/subprocess.py", line 1340, in _execute_child
    raise child_exception
OSError: [Errno 2] No such file or directory

raise child_exception

raise child_exception

shell-True

try:
    arg = get('zenity --entry --entry-text "30 30 30 30" --text "border left, right, top, bottom" --title "Screenshot margins"').strip().split()
except:
    pass
else:
    time.sleep(0.5)
    # frontmost window pos
    frontmost = [l.split()[4] for l in get("xprop -root").splitlines() if "ACTIVE_WINDOW(WINDOW)" in l][0].replace(",", "")
    frontmost = frontmost[:2]+"0"+frontmost[2:]
    f_data = [l.split() for l in get("wmctrl -lG").splitlines() if frontmost in l][0][2:6]
    # extent

# find... while loop, requires find (-print0) and shell (read -d) extensions.
 # Fails on Cygwin; in while loops, filenames ending in \r \n and \n look =.
 # Variable values may be lost unset because loop may run in a subshell.
 find . -print0 | while IFS="" read -r -d "" file ; do ...
   COMMAND "$file" # Use quoted "$file", not $file, everywhere.
 done

$ grep grep .bashrc
    alias grep='grep --color=auto'
    alias fgrep='fgrep --color=auto'
    alias egrep='egrep --color=auto'

try:
 79         filepath = subprocess.check_call(
 80                    [ 'zenity', '--file-selection',
 81                    '--file-filter="*.desktop"',
 82                    '--filename="/usr/share/applications/"' ] )
 83     except subprocess.CalledProcessError:
 84         sys.exit(1)

       -a, --area
              Grab an area of the screen instead of the entire screen.