Python zlib use custom dictionary(pre-defined zdict) example with and without unicode.

main.py

import zlib

#Data for compression
hello = b'hello'


#Compression with dictionary
co = zlib.compressobj(wbits=-zlib.MAX_WBITS, zdict=hello)
compress_data = co.compress(hello) + co.flush()

#Compression without dictionary
co_nodict = zlib.compressobj(wbits=-zlib.MAX_WBITS, )
compress_data_nodict = co_nodict.compress(hello) + co_nodict.flush()
#De-compression with dictionary
do = zlib.decompressobj(wbits=-zlib.MAX_WBITS, zdict=hello)
data = do.decompress(compress_data)

#print compressed output when dict used
print(compress_data)
print('\n')
#print compressed output when dict not used
print(compress_data_nodict)
print('\n')
#print decompressed output when dict used
print(data)

main_unicode.py

#UNICODE EXAMPLE

import zlib

#Data for compression
unicode_data = 'റെക്കോർഡ്'
hello = unicode_data.encode('utf-16be')

#Compression with dictionary
co = zlib.compressobj(wbits=-zlib.MAX_WBITS, zdict=hello)
compress_data = co.compress(hello) + co.flush()

#Compression without dictionary
co_nodict = zlib.compressobj(wbits=-zlib.MAX_WBITS, )
compress_data_nodict = co_nodict.compress(hello) + co_nodict.flush()
#De-compression with dictionary
do = zlib.decompressobj(wbits=-zlib.MAX_WBITS, zdict=hello)
data = do.decompress(compress_data)

#print compressed output when dict used
print(compress_data)
print('\n')
#print compressed output when dict not used
print(compress_data_nodict)
print('\n')
#print decompressed output when dict used
print(data)

Zlib Python Examples.md

IMPORTANT

zdict parameter and keyword argument support added in v3.3. Use python3.

Refences:

1. https://docs.python.org/3/library/zlib.html#zlib.compressobj
2. https://stackoverflow.com/questions/37499818/python-3-4-zlib-deflate-and-shared-dict
3. https://golang.org/pkg/compress/flate/#example__dictionary

Thank you. It's super useful.

Thanks to your example, we at SerpApi found out that zlib with a custom dictionary compressed data even more than zstd with a custom dictionary. (Checked with the small JSON for Sidekiq scheduled jobs.)