Augmented Assignment in Python (PER)
tdelaney at avaya.com
Wed Jul 18 04:30:58 CEST 2001
> "For the built-in types, augmented assignment doesn't violate
> mutability or perform in-place modification of objects. Therefore,
> writing x+=y creates an entirely new object x with the value x + y.
> User defined types and classes may choose to implement different
> behavior by redefining special methods such as __iadd__(),
> and so forth."
> Note: I still stand by the statement for built-in types. I
> looked through
> the Python sources when writing the book and couldn't find any use of
> augmented assignment for built-in types. I am not aware of any
> counter-example where x += y is not equal to x = x + y for
> the standard
> built-in types (if there is such an example, please enlighten me!).
This is very very wrong.
a = 
b = a
a += [1, 2]
List is a built-in type. Lists are modified in-place by augmented
The information in your book will lead to bad programming errors.
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