try.py

import zlib
import zlib_into

a = b'abcde' * 5000
b = bytearray(5000)
res = zlib_into.compress_into(a, b, level=9)

print("res", res)
print(b[:res])

print("Roundtrip", zlib.decompress(b[:res]) == a)

c = bytearray(25001)
res2 = zlib_into.decompress_into(b[:res], c)
print(f"Decompressed {res2} bytes")
print("Roundtrip within zlib_into", bytes(c[:res2]) == a)