zlib

Returns a compression object, to be used for compressing data streams that won’t fit into memory at once.

level is the compression level – an integer from 0 to 9 or -1. A value of 1 (Z_BEST_SPEED) is fastest and produces the least compression, while a value of 9 (Z_BEST_COMPRESSION) is slowest and produces the most. 0 (Z_NO_COMPRESSION) is no compression. The default value is -1 (Z_DEFAULT_COMPRESSION). Z_DEFAULT_COMPRESSION represents a default compromise between speed and compression (currently equivalent to level 6).

method is the compression algorithm. Currently, the only supported value is DEFLATED.

The wbits parameter controls the size of the history buffer (or the “window size”), and what header and trailer format will be used. It has the same meaning as described for compress().

The memLevel argument controls the amount of memory used for the internal compression state. Valid values range from 1 to 9. Higher values use more memory, but are faster and produce smaller output.

strategy is used to tune the compression algorithm. Possible values are Z_DEFAULT_STRATEGY, Z_FILTERED, Z_HUFFMAN_ONLY, Z_RLE (zlib 1.2.0.1) and Z_FIXED (zlib 1.2.2.2).

zdict is a predefined compression dictionary. This is a sequence of bytes (such as a bytes object) containing subsequences that are expected to occur frequently in the data that is to be compressed. Those subsequences that are expected to be most common should come at the end of the dictionary.

Changed in version 3.3: Added the zdict parameter and keyword argument support.