See if a file is a JPG with Python

is_jpeg.py

#is_jpeg.py - Does the file have a JPEG binary signature?

import sys
import binascii

jpeg_signatures = [
    binascii.unhexlify(b'FFD8FFD8'),
    binascii.unhexlify(b'FFD8FFE0'),
    binascii.unhexlify(b'FFD8FFE1')
]

with open(sys.argv[1], 'rb') as file:
    first_four_bytes = file.read(4)

    if first_four_bytes in jpeg_signatures:
        print("JPEG detected.")
    else:
        print("File does not look like a JPEG.")