State of process is Launching when using lldb module in python - lldb

Question

I am learning to use the LLDB.py module in python and am trying to run the following example I found on http://lldb.llvm.org/python-reference. I already added lldb.so to PYTHONPATH. Here is the result I got:
Creating a target for './a.out'
a.out
SBBreakpoint: id = 1, name = 'main', module = a.out, locations = 1
SBProcess: pid = 0, state = launching, threads = 0, executable = a.out
It seems like the program doesn't get started, the state of process is always Launching. Is there any configuration problems or any missing codes?
import lldb
import os
def disassemble_instructions(insts):
for i in insts:
print i
# Set the path to the executable to debug
exe = "./a.out"
# Create a new debugger instance
debugger = lldb.SBDebugger.Create()
# When we step or continue, don't return from the function until the process
# stops. Otherwise we would have to handle the process events ourselves which, while doable is
#a little tricky. We do this by setting the async mode to false.
debugger.SetAsync (False)
# Create a target from a file and arch
print "Creating a target for '%s'" % exe
target = debugger.CreateTargetWithFileAndArch (exe, lldb.LLDB_ARCH_DEFAULT)
if target:
# If the target is valid set a breakpoint at main
main_bp = target.BreakpointCreateByName ("main", target.GetExecutable().GetFilename());
print main_bp
# Launch the process. Since we specified synchronous mode, we won't return
# from this function until we hit the breakpoint at main
process = target.LaunchSimple (["./story.txt"], None, os.getcwd())
# Make sure the launch went ok
if process:
# Print some simple process info
state = process.GetState ()
print process
if state == lldb.eStateStopped:
# Get the first thread
thread = process.GetThreadAtIndex (0)
if thread:
# Print some simple thread info
print thread
# Get the first frame
frame = thread.GetFrameAtIndex (0)
if frame:
# Print some simple frame info
print frame
function = frame.GetFunction()
# See if we have debug info (a function)
if function:
# We do have a function, print some info for the function
print function
# Now get all instructions for this function and print them
insts = function.GetInstructions(target)
disassemble_instructions (insts)
else:
# See if we have a symbol in the symbol table for where we stopped
symbol = frame.GetSymbol();
if symbol:
# We do have a symbol, print some info for the symbol
print symbol
}