ZstdCompressionParameters

Zstandard offers a high-level compression level that maps to lower-level compression parameters. For many consumers, this numeric level is the only compression setting you’ll need to touch.

But for advanced use cases, it might be desirable to tweak these lower-level settings.

The ZstdCompressionParameters type represents these low-level compression settings.

class zstandard.ZstdCompressionParameters(format=0, compression_level=0, window_log=0, hash_log=0, chain_log=0, search_log=0, min_match=0, target_length=0, strategy=-1, write_content_size=1, write_checksum=0, write_dict_id=0, job_size=0, overlap_log=-1, force_max_window=0, enable_ldm=0, ldm_hash_log=0, ldm_min_match=0, ldm_bucket_size_log=0, ldm_hash_rate_log=-1, threads=0)

Low-level zstd compression parameters.

This type represents a collection of parameters to control how zstd compression is performed.

Instances can be constructed from raw parameters or derived from a base set of defaults specified from a compression level (recommended) via ZstdCompressionParameters.from_level().

>>> # Derive compression settings for compression level 7.
>>> params = zstandard.ZstdCompressionParameters.from_level(7)

>>> # With an input size of 1MB
>>> params = zstandard.ZstdCompressionParameters.from_level(7, source_size=1048576)

Using from_level(), it is also possible to override individual compression parameters or to define additional settings that aren’t automatically derived. e.g.:

>>> params = zstandard.ZstdCompressionParameters.from_level(4, window_log=10)
>>> params = zstandard.ZstdCompressionParameters.from_level(5, threads=4)

Or you can define low-level compression settings directly:

>>> params = zstandard.ZstdCompressionParameters(window_log=12, enable_ldm=True)

Once a ZstdCompressionParameters instance is obtained, it can be used to configure a compressor:

>>> cctx = zstandard.ZstdCompressor(compression_params=params)

Some of these are very low-level settings. It may help to consult the official zstandard documentation for their behavior. Look for the ZSTD_p_* constants in zstd.h (https://github.com/facebook/zstd/blob/dev/lib/zstd.h).

chain_log

compression_level

enable_ldm

estimated_compression_context_size()

Estimated size in bytes needed to compress with these parameters.

force_max_window

format

static from_level(level, source_size=0, dict_size=0, **kwargs)

Create compression parameters from a compression level.

Parameters:

• level – Integer compression level.
• source_size – Integer size in bytes of source to be compressed.
• dict_size – Integer size in bytes of compression dictionary to use.

Returns:

ZstdCompressionParameters

hash_log

job_size

ldm_bucket_size_log

ldm_hash_log

ldm_hash_rate_log

ldm_min_match

min_match

overlap_log

search_log

strategy

target_length

threads

window_log

write_checksum

write_content_size

write_dict_id