casting byte array to signed short in python

Question

I want to convert a bytearray type or a list of binary strings in python to a signed short list. In fact, I am getting a byte stream from Ethernet and I want to convert them in signed short; however, the only way I found in Python is using struct.unpack which seems to be slow since it requires a format string to determine the type of each byte.

This format requirement slows in two steps:

1) Required to make a long string for a long array of bytes

2) Required to search one-by-one in the array.

In C++, the following simple code does the job on the entire memory block contained by InBuf:

OutBuf = short int[len]
InBuf = char[len*2]
memcpy(&OutBuf, &InBuf, len*2)

This skips doing the format search within the byte array as well as the format string construction. Does anyone know a better way to do so in Python?

Cody Gray · Accepted Answer · 2019-03-07 19:52:25Z

1

If you're using Python > 3.2 you could use int.from_bytes:

int.from_bytes(b, byteorder='little', signed=True)

edited Mar 7, 2019 at 19:52

Cody Gray♦

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answered Feb 25, 2019 at 18:56

l'L'l

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1 Comment

eleaut Over a year ago

This does not work since I have a binary string or a list of binary strings likeMyBin = b'12wda121q' or MyBin = [b'12was',b'1231ws'] and int.from_bytes should be applied on the 2-byte slices to get the true conversion I need. This is still very slow.

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