On 03/07/2014 10:35, candide wrote:
>From that link:
"""
An augmented assignment expression like x += 1 can be rewritten as x =
x + 1 to achieve a similar, but not exactly equal effect. In the
augmented version, x is only evaluated once. Also, when possible, the
actual operation is performed in-place, meaning that rather than
creating a new object and assigning that to the target, the old object
is modified instead.
"""
The significance here is that the augmented assignment may not
necessarily be at all comparable to the non-augmented version, but
ought to have *approximately* the same *intention*.
This is not my reading.
of situations where the two will differ, eg when there are multiple
references to the same object:
a = b = [1,2]
a += [3]
a,b
([1, 2, 3], [1, 2, 3])
a = a + [4]
a,b
([1, 2, 3, 4], [1, 2, 3])
OK but this behavior is in conformance with the Reference Manual (cf. your quote above : "when
possible, the actual operation is performed in-place"). This is not my point because the doc
explictly claims that "an augmented assignment [...] performs the binary operation specific to
the type of assignment on the two operands".
To get the wording changed to satisfy yourself, either raise an issue on
the bug tracker at bugs.python.org and attach a patch file, or send an
email with suggested wording to d...@python.org.
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