>>> import struct
>>> fmt = '<3s3sHH'  # 1
>>> with open('filter.gif', 'rb') as fp:
...     img = memoryview(fp.read())  # 2
...
>>> header = img[:10]  # 3
>>> bytes(header)  # 4
b'GIF89a+\x02\xe6\x00'
>>> struct.unpack(fmt, header)  # 5
(b'GIF', b'89a', 555, 230)
>>> del header  # 6
>>> del img