import random,zipfile

filesize=4097
testsize=4096

junk =  (("%%0%dX" % (filesize * 2)) % random.getrandbits(filesize * 8)).decode("hex")

with zipfile.ZipFile('test.zip','w',zipfile.ZIP_DEFLATED) as f:
    f.writestr('foo',junk)
    fp=f.open('foo','r')
    buf=fp.read(testsize)
    assert len(buf)<=testsize,'Read returned %d bytes (%d requested)'%(len(buf),testsize)