bpo-47040: improve document of checksum functions (gh-31955)

Clarifies a versionchanged note on crc32 & adler32 docs that the workaround is only needed for Python 2 and earlier.
Also cleans up an unnecessary intermediate variable in the implementation.

Authored-By: Ma Lin / animalize
Co-authored-by: Gregory P. Smith <greg@krypto.org>

2 files changed, 9 insertions, 12 deletions

diff --git a/Doc/library/binascii.rst b/Doc/library/binascii.rst
index 62d7efe..19efc2d 100644
--- a/Doc/library/binascii.rst
+++ b/Doc/library/binascii.rst
@@ -107,7 +107,7 @@ The :mod:`binascii` module defines the following functions:
 
 .. function:: crc32(data[, value])
 
-   Compute CRC-32, the 32-bit checksum of *data*, starting with an
+   Compute CRC-32, the unsigned 32-bit checksum of *data*, starting with an
    initial CRC of *value*.  The default initial CRC is zero.  The algorithm
    is consistent with the ZIP file checksum.  Since the algorithm is designed for
    use as a checksum algorithm, it is not suitable for use as a general hash
@@ -121,9 +121,8 @@ The :mod:`binascii` module defines the following functions:
 
    .. versionchanged:: 3.0
       The result is always unsigned.
-      To generate the same numeric value across all Python versions and
-      platforms, use ``crc32(data) & 0xffffffff``.
-
+      To generate the same numeric value when using Python 2 or earlier,
+      use ``crc32(data) & 0xffffffff``.
 
 .. function:: b2a_hex(data[, sep[, bytes_per_sep=1]])
               hexlify(data[, sep[, bytes_per_sep=1]])
diff --git a/Doc/library/zlib.rst b/Doc/library/zlib.rst
index 793c90f..f0c67d5 100644
--- a/Doc/library/zlib.rst
+++ b/Doc/library/zlib.rst
@@ -42,10 +42,9 @@ The available exception and functions in this module are:
    for use as a general hash algorithm.
 
    .. versionchanged:: 3.0
-      Always returns an unsigned value.
-      To generate the same numeric value across all Python versions and
-      platforms, use ``adler32(data) & 0xffffffff``.
-
+      The result is always unsigned.
+      To generate the same numeric value when using Python 2 or earlier,
+      use ``adler32(data) & 0xffffffff``.
 
 .. function:: compress(data, /, level=-1, wbits=MAX_WBITS)
 
@@ -137,10 +136,9 @@ The available exception and functions in this module are:
    for use as a general hash algorithm.
 
    .. versionchanged:: 3.0
-      Always returns an unsigned value.
-      To generate the same numeric value across all Python versions and
-      platforms, use ``crc32(data) & 0xffffffff``.
-
+      The result is always unsigned.
+      To generate the same numeric value when using Python 2 or earlier,
+      use ``crc32(data) & 0xffffffff``.
 
 .. function:: decompress(data, /, wbits=MAX_WBITS, bufsize=DEF_BUF_SIZE)