If you want to call a function named GetRate, you can do it as:

from ctypes import *
from ctypes.wintypes import *

GetRate = windll.YOURLIB.GetRate
GetRate.restype = c_int
GetRate.argtypes = [HANDLE, POINTER(c_int)]

# now call GetRate as something like:
#
# hDev = ... # handle
# Data = c_int()
#
# GetRate(hDev, byref(Data)) # GetRate(hDev, &Data)
# print Data

but if you try to declare a callback, function pointer, you can do it as (I think you're looking for the first):

from ctypes import *
from ctypes.wintypes import *

def GetRate(hDev, pDate):
    # Your implementation
    return 0

# you'll need GETRATE to pass it in the argtypes to the target function
GETRATE = WINFUNCTYPE(c_int, HANDLE, POINTER(c_int))
pGetRate = GETRATE(GetRate)

# now you can pass pGetRate as a callback to another function

You can use ctypes.cast(addr, type). I'll extend your example to acquire an address via a known object, to demonstrate:

INTP = ctypes.POINTER(ctypes.c_int)
num = ctypes.c_int(42)
addr = ctypes.addressof(num)
print 'address:', addr, type(addr)
ptr = ctypes.cast(addr, INTP)
print 'pointer:', ptr
print 'value:', ptr[0]

Output:

address: 4301122528 <type 'int'>
pointer: <__main__.LP_c_int object at 0x1005decb0>
value: 42

>>> platform.architecture()
('64bit', 'WindowsPE')
>>> ctypes.sizeof(ctypes.c_int*4)
16
>>> ctypes.sizeof(ctypes.POINTER(ctypes.c_int))
8

Clearly, these are different entities. Specifically, an array cannot be returned from a C function since it doesn't fit into a register.

In the 2nd case, your result is your returned int* saved somewhere by ctypes and interpreted as int[4]: the 1st is your pointer, further are some garbage at the following addresses. On x64, the 1st is one DWORD of the address, the next is the other DWORD (which is which depends on your endianness), the rest are garbage.

Define b as a pointer in the first place.

#coding=utf-8

import ctypes
from ctypes import *

if __name__ == "__main__":
    lib = ctypes.CDLL("./test.so")
    a = c_int()
    b = pointer(c_int())
    lib.test_2(
        byref(a),
        byref(b)
    )
    for index in range(0,a.value):
      print b[index]