Question

I am trying to talk to a device using python. I have been handed a tuple of bytes which contains the storage information. How can I convert the data into the correct values:

response = (0, 0, 117, 143, 6)

The first 4 values are a 32-bit int telling me how many bytes have been used and the last value is the percentage used.

I can access the tuple as response[0] but cannot see how I can get the first 4 values into the int I require.

Answer 1

See Convert Bytes to Floating Point Numbers in Python

You probably want to use the struct module, e.g.

import struct  response = (0, 0, 117, 143, 6) struct.unpack('>I', ''.join([chr(x) for x in response[:-1]])) 

Assuming an unsigned int. There may be a better way to do the conversion to unpack, a list comprehension with join was just the first thing that I came up with.

EDIT: See also ΤΖΩΤΖΙΟΥ’s comment on this answer regarding endianness as well.

EDIT #2: If you don’t mind using the array module as well, here is an alternate method that obviates the need for a list comprehension. Thanks to @JimB for pointing out that unpack can operate on arrays as well.

import struct from array import array  response = (0, 0, 117, 143, 6) bytes = array('B', response[:-1]) struct.unpack('>I', bytes)