Reading 4 Byte Integers From Binary File In Python

I have a some sets of binary files (some are potentially large (100MB)) that contain 4 byte integers. Can anyone supply a code snippet to show how to extract each 4 byte integer un

Solution 1:

You could use struct.unpack():

withopen(filename, 'rb') as fileobj:
    for chunk initer(lambda: fileobj.read(4), ''):
        integer_value = struct.unpack('<I', chunk)[0]

This uses <I to interpret the bytes as little-endian unsigned integers. Adjust the format as needed; > for big-endian, i for signed integers.

If you need to read a lot of integer values in one go and know how many you need to read, take a look at the array module as well:

fromarray import array

arr =array('L')
withopen(filename, 'rb') as fileobj:
    arr.fromfile(fileobj, number_of_integers_to_read)

where you'd need to use array.byteswap() if the endianess of the file and your system didn't match:

ifsys.byteorder!='little':arr.byteswap()

Solution 2:

Check out the NumPy fromfile function. You provide a simple type annotation about the data to be read, and the function efficiently reads it into a NumPy ndarray object.

import numpy as np
np.fromfile(file_name, dtype='<i4')

You can change dtype to reflect size and byte order as well. See here for some examples.