merge #17973: fix technical inaccuracy in faq entry (it now passes doctest).

This commit is contained in:
R David Murray 2013-05-21 11:45:09 -04:00
commit b3a579223e
1 changed files with 8 additions and 5 deletions

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@ -1131,7 +1131,7 @@ a tuple points to.
Under the covers, what this augmented assignment statement is doing is
approximately this::
>>> result = a_tuple[0].__iadd__(1)
>>> result = a_tuple[0] + 1
>>> a_tuple[0] = result
Traceback (most recent call last):
...
@ -1154,16 +1154,19 @@ that even though there was an error, the append worked::
>>> a_tuple[0]
['foo', 'item']
To see why this happens, you need to know that for lists, ``__iadd__`` is equivalent
to calling ``extend`` on the list and returning the list. That's why we say
that for lists, ``+=`` is a "shorthand" for ``list.extend``::
To see why this happens, you need to know that (a) if an object implements an
``__iadd__`` magic method, it gets called when the ``+=`` augmented assignment
is executed, and its return value is what gets used in the assignment statement;
and (b) for lists, ``__iadd__`` is equivalent to calling ``extend`` on the list
and returning the list. That's why we say that for lists, ``+=`` is a
"shorthand" for ``list.extend``::
>>> a_list = []
>>> a_list += [1]
>>> a_list
[1]
is equivalent to::
This is equivalent to::
>>> result = a_list.__iadd__([1])
>>> a_list = result