Reading 32 bit signed ieee 754 floating points from a binary file with python?

Question

I have a binary file which is simple a list of signed 32 bit ieee754 floating point numbers. They are not separated by anything, and simply appear one after another until EOF.

How would I read from this file and interpret them correctly as floating point numbers?

I tried using read(4), but it automatically converts them to a string with ascii encoding.

I also tried using bytearray but that only takes it in 1 byte at a time instead of 4 bytes at a time as I need.

Asked By: Razor Storm

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Source

Answer 1

Take a peek at struct.unpack. Something like the following might work…

f = struct.unpack('f', data_read)

Answered By: Andrew White

Answer 2

struct.unpack('f', file.read(4))

You can also unpack several at once, which will be faster:

struct.unpack('f'*n, file.read(4*n))

Answered By: Marcelo Cantos

Answer 3

import struct
(num,) = struct.unpack('f', f.read(4))

Answered By: Chris Eberle

Answer 4

The fastest approach (in terms of performance) I found so far is numpy.fromfile

import numpy as np

class FloatReader:
    def __init__(self, filename):
        self.f = open(filename, "rb")
    
    def read_floats(self, count : int):
        return np.fromfile(self.f, dtype=np.float32, count=count, sep='')

This approach is much faster than struct.unpack in terms of performance!

Answered By: Anatoly

Reading 32 bit signed ieee 754 floating points from a binary file with python?

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