PEP 467: motivation, rationale, remove discouragement (GH-2069)

* add rationale and motivation sections
* "discouragement" removed (feedback from rhettinger)

pep-0467.txt

@@ -14,48 +14,44 @@ Post-History: 2014-03-30 2014-08-15 2014-08-16 2016-06-07 2016-09-01 2021-04-13
 Abstract
 ========
 
-During the initial development of the Python 3 language specification, the
-core ``bytes`` type for arbitrary binary data started as the mutable type
-that is now referred to as ``bytearray``. Other aspects of operating in
-the binary domain in Python have also evolved over the course of the Python
-3 series.
-
 This PEP proposes five small adjustments to the APIs of the ``bytes`` and
 ``bytearray`` types to make it easier to operate entirely in the binary domain:
 
-* Discourage passing single integer values to ``bytes`` and ``bytearray``
 * Add ``bytes.fromsize`` and ``bytearray.fromsize`` alternative constructors
 * Add ``bytes.fromint`` and ``bytearray.fromint`` alternative constructors
 * Add ``bytes.getbyte`` and ``bytearray.getbyte`` byte retrieval methods
 * Add ``bytes.iterbytes`` and ``bytearray.iterbytes`` alternative iterators
 
 
-Proposals
+Rationale
 =========
 
-Discourage use of current "zero-initialised sequence" behavior
----------------------------------------------------------------
+During the initial development of the Python 3 language specification, the
+core ``bytes`` type for arbitrary binary data started as the mutable type
+that is now referred to as ``bytearray``. Other aspects of operating in
+the binary domain in Python have also evolved over the course of the Python
+3 series, for example with PEP 461.
 
-Currently, the ``bytes`` and ``bytearray`` constructors accept an integer
-argument and interpret it as meaning to create a zero-initialised sequence
-of the given size::
 
-    >>> bytes(3)
-    b'\x00\x00\x00'
-    >>> bytearray(3)
-    bytearray(b'\x00\x00\x00')
+Motivation
+==========
 
-This PEP proposes to update the documentation to discourage making use of that
-input type dependent behavior in Python 3.11, suggesting to use a new, more
-explicit, ``bytes.fromsize(n)`` or ``bytearray.fromsize(n)`` spelling instead
-(see next section).
+With Python 3 and the split between ``str`` and ``bytes``, one small but
+important area of programming became slightly more difficult, and much more
+painful -- wire format protocols.
 
-However, the current handling of numeric inputs in the default constructors
-would remain in place indefinitely to avoid introducing a compatibility break.
+This area of programming is characterized by a mixture of binary data and
+ASCII compatible segments of text (aka ASCII-encoded text).  The addition of
+the new constructors, methods, and iterators will aid both in writing new
+wire format code, and in porting any remaining Python 2 wire format code.
 
-No other changes are proposed to the existing constructors.
+Common use-cases include ``dbf`` and ``pdf`` file formats, ``email``
+formats, and ``FTP`` and ``HTTP`` communications, among many others.
 
 
+Proposals
+=========
+
 Addition of explicit "count and byte initialised sequence" constructors
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