Python: How to convert bytes to integer arrays efficiently?

Question

I have read a binary file from disk. Which produces a bytes variable e.g.

arr = open(file, "rb").read()

Now arr is structured such that each 4-byte form a 32bit integer (little endian). I see there is function int.from_bytes to convert bytes to int but it is too slow.

Is there a function to convert bytes to an integer array? Numpy solutions welcome.

In contrast, this seems easy to do in R and Julia e.g.

In R

readBin(arr, what="integer", n=length(arr)/4)

In Julia

reinterpret(Int32, arr)

See Python array module. Format code for 4-byte signed ints is 'l'. The .frombytes() method for what you asked, or the .fromfile() method to construct directly by a reading from an open binary-mode file. — Tim Peters
– Tim Peters, Commented Apr 26, 2020 at 4:06

xiaodai · Accepted Answer · 2020-04-26 04:42:04Z

1

Based on @Tim Peter's answer it is

b = array.array("i")
b.frombytes(arr)

Now b is an array of int.

See documentation here https://docs.python.org/3/library/array.html#module-array

answered Apr 26, 2020 at 4:42

xiaodai

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