gzip.compress incorrectly ignores level parameter

[rhpvorderman]

BPO	46267
Nosy	@rhpvorderman
PRs	bpo-46267: Correctly use compresslevel in gzip.compress  #30416

^{Note: these values reflect the state of the issue at the time it was migrated and might not reflect the current state.}

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GitHub fields:

assignee = None
closed_at = None
created_at = <Date 2022-01-05.11:14:04.627>
labels = ['type-bug', 'library', '3.11']
title = 'gzip.compress incorrectly ignores level parameter'
updated_at = <Date 2022-03-02.14:33:46.499>
user = 'https://github.com/rhpvorderman'

bugs.python.org fields:

activity = <Date 2022-03-02.14:33:46.499>
actor = 'rhpvorderman'
assignee = 'none'
closed = False
closed_date = None
closer = None
components = ['Library (Lib)']
creation = <Date 2022-01-05.11:14:04.627>
creator = 'rhpvorderman'
dependencies = []
files = []
hgrepos = []
issue_num = 46267
keywords = ['patch']
message_count = 2.0
messages = ['409749', '414361']
nosy_count = 1.0
nosy_names = ['rhpvorderman']
pr_nums = ['30416']
priority = 'normal'
resolution = None
stage = 'patch review'
status = 'open'
superseder = None
type = 'behavior'
url = 'https://bugs.python.org/issue46267'
versions = ['Python 3.11']

[rhpvorderman]

def compress(data, compresslevel=_COMPRESS_LEVEL_BEST, *, mtime=None):
    """Compress data in one shot and return the compressed string.

compresslevel sets the compression level in range of 0-9.
mtime can be used to set the modification time. The modification time is
set to the current time by default.
"""
if mtime == 0:
    # Use zlib as it creates the header with 0 mtime by default.
    # This is faster and with less overhead.
    return zlib.compress(data, level=compresslevel, wbits=31)
header = _create_simple_gzip_header(compresslevel, mtime)
trailer = struct.pack("<LL", zlib.crc32(data), (len(data) & 0xffffffff))
# Wbits=-15 creates a raw deflate block.
return header + zlib.compress(data, wbits=-15) + trailer
                                   ^ 
                                   Level should be here

I noticed this while benchmarking against python-isal. This benchmarks add level 1 and it seemed oddly slow.

This can be fixed easily. PR coming up.

[rhpvorderman]

ping