Python byte array to integer conversion (TFTP Client)

Question

I am trying to set up a TFTP client using Python 2.7.
Problem is when I receive data packet, it is in the form of byte array of integers. For example: '\x03\x00\x01'. I want to convert each byte of byte array string to corresponding integer value.

I tried this method:

receiving_pack = '\x03\x00\x01'
int(receiving_pack[0], 16)

But I got following error message:

ValueError: invalid literal for int() with base 16: '\x03'

I tried another method:

struct.unpack(h, receiving_pack[0])[0]

But got error:

error: unpack requires a string argument of length 2

This is likely a duplicate [of this question](http://stackoverflow.com/a/11826089/4607534) — pantalohnes, May 19 '17 at 14:53
I tried that method (struct.unpack) but got another error: unpack requires a string argument of length 2 — raja, May 19 '17 at 14:59

score 1 · Answer 1 · answered Aug 10 '17 at 18:39

Your format string is incorrect. It must be in quotes (obvious) and the count of bytes it defines MUST match number of bytes in the byte string.

Use unpack to convert the byte string b'\x03\x00\x01' to integers,

Using Python 3.6:

>>>import struct
>>>i = struct.unpack('<BBB', b'\x03\x00\x01')
>>>print(i)
(3,0,1)

struct has been around since Python 2.7, so you shouldn't have a problem. The format string '

score 0 · Answer 2 · answered May 19 '17 at 16:22

0

The best method would be:

receiving_pack = '\x03\x00\x01'

to convert this to integers byte by byte:

map(ord, receiving_pack)
-> [3, 0, 1]

answered May 19 '17 at 16:22

raja

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score 0 · Accepted Answer · answered Aug 10 '17 at 18:42

0

Convert to a bytearray and then index or iterate.

>>> nums = bytearray('\x03\x00\x01')
>>> nums[0]
3
>>> nums[1]
0
>>> nums[2]
1

answered Aug 10 '17 at 18:42

Ignacio Vazquez-Abrams

776,304
153
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Python byte array to integer conversion (TFTP Client)

3 Answers3