Issue #26244: Clarify default zlib compression level in documentation
Based on patch by Aviv Palivoda.
diff --git a/Doc/library/zlib.rst b/Doc/library/zlib.rst
index a815d1f..1869bb8 100644
--- a/Doc/library/zlib.rst
+++ b/Doc/library/zlib.rst
@@ -60,10 +60,11 @@
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``. A value
- of ``1`` is fastest and produces the least compression, while a value of
+ *level* is the compression level -- an integer from ``0`` to ``9`` or ``-1``.
+ A value of ``1`` is fastest and produces the least compression, while a value of
``9`` is slowest and produces the most. ``0`` is no compression. The default
- value is ``6``.
+ 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``.