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| -rw-r--r-- | Doc/faq/programming.rst | 1 | ||||
| -rw-r--r-- | Doc/reference/datamodel.rst | 12 |
2 files changed, 8 insertions, 5 deletions
diff --git a/Doc/faq/programming.rst b/Doc/faq/programming.rst index 42e55d6d6f..280d5e13d2 100644 --- a/Doc/faq/programming.rst +++ b/Doc/faq/programming.rst @@ -1103,6 +1103,7 @@ Use a list comprehension:: result = [obj.method() for obj in mylist] +.. _faq-augmented-assignment-tuple-error: Why does a_tuple[i] += ['item'] raise an exception when the addition works? --------------------------------------------------------------------------- diff --git a/Doc/reference/datamodel.rst b/Doc/reference/datamodel.rst index 22cac07030..160af305d8 100644 --- a/Doc/reference/datamodel.rst +++ b/Doc/reference/datamodel.rst @@ -2023,11 +2023,13 @@ left undefined. ``&=``, ``^=``, ``|=``). These methods should attempt to do the operation in-place (modifying *self*) and return the result (which could be, but does not have to be, *self*). If a specific method is not defined, the augmented - assignment falls back to the normal methods. For instance, to execute the - statement ``x += y``, where *x* is an instance of a class that has an - :meth:`__iadd__` method, ``x.__iadd__(y)`` is called. If *x* is an instance - of a class that does not define a :meth:`__iadd__` method, ``x.__add__(y)`` - and ``y.__radd__(x)`` are considered, as with the evaluation of ``x + y``. + assignment falls back to the normal methods. For instance, if *x* is an + instance of a class with an :meth:`__iadd__` method, ``x += y`` is equivalent + to ``x = x.__iadd__(y)`` . Otherwise, ``x.__add__(y)`` and ``y.__radd__(x)`` + are considered, as with the evaluation of ``x + y``. In certain situations, + augmented assignment can result in unexpected errors (see + :ref:`faq-augmented-assignment-tuple-error`), but this behavior is in + fact part of the data model. .. method:: object.__neg__(self) |