Now I've just discovered there is the same problem with the
array.array() type (see following code).


import bz2, threading, array

bz2c = bz2.BZ2Compressor()
# Span at least a whole arena (256KB long)
junk_len = 512 * 1024
junk = array.array("c", b"a") * junk_len
empty = array.array("c")
buf = empty[:]

for x in range(50):
    buf[:] = junk
    t = threading.Thread(target=bz2c.compress, args=[buf])
    t.start()
    buf[:] = empty
    t.join()