Python script converts bin file endianness

• Modified from here

#!/bin/python3

import struct
import sys
import os


if sys.argv.__len__() > 1:
    src_file = sys.argv[1]

    if sys.argv.__len__() > 2:
        dst_file = sys.argv[2]
    else:
        dst_file = src_file[0:(src_file.__len__()-4)]
        dst_file += "_covert.bin"
else:
    print('Usage: ' + sys.argv[0] + ' input.bin output.bin')
    exit(1)

if not os.path.exists(src_file):
    print('File Path Invalid! Exiting...')
    exit(1)

if src_file == dst_file:
    print(src_file + ' ' + dst_file + ' same')
    exit(1)


#print("Source file: {0}\nTarget File: {1}\n".format(src_file, dst_file))

try:
    sf = open(src_file, "rb")
    df = open(dst_file, "wb")

    buf_tmp = [b'0' for x in range(0, 4)]
    contents = sf.read()
    buf_size = contents.__len__()

    extra_size = (buf_size % 4)
    if extra_size > 0:
        buf_size += (4 - extra_size)
        contents = contents + b'0000'

    for i in range(0, buf_size, 4):
        buf_tmp[3] = contents[i]
        buf_tmp[2] = contents[i+1]
        buf_tmp[1] = contents[i+2]
        buf_tmp[0] = contents[i+3]

        tmp_bytes = struct.pack("4B", buf_tmp[0], buf_tmp[1], buf_tmp[2], buf_tmp[3])
        df.write(tmp_bytes)

finally:
    if sf:
        sf.close()
    if df:
        df.close()

    exit(0)