如何在python中将16位无符号整数拆分为字节数组？

Question

I need to split a 16-bit unsigned integer into an array of bytes (ie array.array('B') ) in python.

For example:

>>> reg_val = 0xABCD
[insert python magic here]
>>> print("0x%X" % myarray[0])
0xCD
>>> print("0x%X" % myarray[1])
0xAB

The way I'm currently doing it seems very complicated for something so simple:

>>> import struct
>>> import array
>>> reg_val = 0xABCD
>>> reg_val_msb, reg_val_lsb = struct.unpack("<BB", struct.pack("<H", (0xFFFF & reg_val)))
>>> myarray = array.array('B')
>>> myarray.append(reg_val_msb)
>>> myarray.append(reg_val_lsb)

Is there a better/more efficient/more pythonic way of accomplishing the same thing?

Answer 1

For non-complex numbers you can use divmod(a, b) , which returns a tuple of the quotient and remainder of arguments.

The following example uses map() for demonstration purposes. In both examples we're simply telling divmod to return a tuple (a/b, a%b), where a=0xABCD and b=256 .

>>> map(hex, divmod(0xABCD, 1<<8)) # Add a list() call here if your working with python 3.x
['0xab', '0xcd']

# Or if the bit shift notation is distrubing:
>>> map(hex, divmod(0xABCD, 256))

Or you can just place them in the array:

>>> arr = array.array('B')
>>> arr.extend(divmod(0xABCD, 256))
>>> arr
array('B', [171, 205])

Answer 2

(using python 3 here, there are some nomenclature differences in 2)

Well first, you could just leave everything as bytes . This is perfectly valid:

reg_val_msb, reg_val_lsb = struct.pack('<H', 0xABCD)

bytes allows for "tuple unpacking" (not related to struct.unpack , tuple unpacking is used all over python). And bytes is an array of bytes, which can be accessed via index as you wanted.

b = struct.pack('<H',0xABCD)

b[0],b[1]
Out[52]: (205, 171)

If you truly wanted to get it into an array.array('B') , it's still rather easy:

ary = array('B',struct.pack('<H',0xABCD))
# ary = array('B', [205, 171])

print("0x%X" % ary[0])
# 0xCD

Answer 3

You can write your own function like this.

def binarray(i):
    while i:
        yield i & 0xff
        i = i >> 8

print list(binarray(0xABCD))
#[205, 171]